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Information And Message Center

Overview 

The message center is an integral part of the IPC that receives and acts upon much of the same information that is input and used to operate the IPC gauges, indicators, and warning indicators. The message center uses both hardwired and the network based inputs to receive information.

The message center functionality is controlled through the message center switch (part of the LH steering wheel switch), which is hardwired to the SCCM through input and return circuits.

Whenever conditions are present that require a warning message, the message center replaces the last selected display with the new warning display. Once the message is reset or cleared, the message center returns to the last selected display. If multiple warnings are present, the message center displays each warning for approximately 4 seconds. Warning messages are also generally associated with other observable outputs of the IPC (gauges, indicators and Reconfigurable Telltale (RTT) indicators). For example, when the BCM detects a low brake fluid condition, the BCM sends the IPC a request to illuminate the brake warning indicator and a request to display the low brake fluid message in the message center. This allows the message center to be a more informative supplement to the IPC gauges and indicators.

Another function of the message center is to display Reconfigurable Telltales (RTTs). Similar to the interaction between the message center and the standard warning indicators, the message center often displays a warning message and the Reconfigurable Telltale (RTT) at the same time. For example, if the PCM detects low engine oil pressure, the PCM sends a request to the IPC to illuminate the low oil pressure Reconfigurable Telltale (RTT) and to display the low oil pressure message in the message center. If multiple warnings are present requiring multiple Reconfigurable Telltale (RTTs), the message center cycles or rotates through the displays in the same manner the message center cycles the text messages.

System Warning Messages 

The system warning messages alert the operator to possible problems or malfunctions in the vehicle operating systems. System warning messages may be stand alone messages but are often associated with another form of indication such as a gauge, an indicator or Reconfigurable Telltale (RTT). The message center displays the last selected feature if there are no additional warning messages. Once a warning message has been displayed, the message must be acknowledged to allow full functionality of the message center. Press the OK button to acknowledge and clear the warning message.

Refer to the Owner's Literature for a complete list of the messages.

System Operation 

System Diagram 

GFD31567Courtesy of FORD MOTOR COMPANY

Network Message Chart Module Network Input Messages - IPC 

Broadcast Message Originating Module Message Purpose
2WD indicator TCCM Input used to control the 2WD indicator.
4x4 auto indicator TCCM Input used to control the 4x4 auto indicator.
4x4 high indicator TCCM Input used to control the 4x4 high indicator.
4x4 low indicator TCCM Input used to control the 4x4 low indicator.
4x4 range fault TCCM Engine input used to control the powertrain malfunction (wrench) Reconfigurable Telltale (RTT) and to display the check 4x4 message.
4x4 status indication TCCM Input used to display the status messages related to the neutral tow function.
Adaptive headlamps HCM Input used to display the check headlamps message.
Average fuel economy reset BCM Input used by the IPC to confirm the driver request to reset the Average Fuel Economy (AFE).
Battery charge low BCM Input used to control the charging system Reconfigurable Telltale (RTT), charging system fault message load shed message display.
BLIS ® side detection sensor status BCM Input used to display the BLIS ® fault warning messages.
Brake chime request ABS module Input used to display the service AdvanceTrac ® message.
Brake fluid level low indicator BCM Input used to display the brake fluid level low warning message.
Brake lamp request ABS module Input used to display the check brake system warning message associated with an ABS concern.
CTA BCM Input used to display the CTA operational warning messages and fault warning messages.
Cruise control set speed display PCM Input used to display the cruise control set speed.
Cruise control status display PCM Input used to control the cruise control Reconfigurable Telltale (RTT).
Driver door ajar BCM Input used to control the door ajar Reconfigurable Telltale (RTT) and warning message for the driver door ajar input. Input used to display the PRNDL not in park message.
Driver rear door ajar BCM Input used to control the door ajar Reconfigurable Telltale (RTT) and warning message for the LH rear door ajar input.
Engine coolant temperature PCM Input used to control the engine over-temperature Reconfigurable Telltale (RTT) and warning message.
Engine oil life percent PCM Input used to display the engine oil change messages.
Engine oil temperature PCM Input used to control the engine oil temperature display.
Engine service required PCM Engine input used to control the powertrain malfunction (wrench) Reconfigurable Telltale (RTT) and to display the see manual message.
Engine speed PCM Input used by the IPC to calculate and display the engine hours and engine idle hours.
EPAS fault PSCM Input used to display the steering system messages.
Fuel alcohol percent PCM Input used by the IPC for the calculation of the DTE.
Fuel fill inlet indication PCM Input used to display the check fuel fill inlet message.
Fuel flow volume display PCM Input used by the IPC to calculate the Average Fuel Economy (AFE) and DTE.
GPS direction GPSM Input used to display the compass direction.
Hill descent message display ABS module Input used to control the hill descent Reconfigurable Telltale (RTT) and to display the hill descent status messages.
Ignition key type BCM Input used by the IPC to determine if a MyKey ® is used when requesting a reset of the Average Fuel Economy (AFE).
Ignition status BCM Ignition RUN, START and accessory states required for the IPC and message center operating modes and fault reporting.Input used to determine the ignition state for the PRNDL not in park message.
IKT programming status BCM Input used to display the could not program the integrated key message.
Keycode status BCM Input used to display the keypad factory code.
Liftgate ajar BCM Input used to control the door ajar Reconfigurable Telltale (RTT) and warning message for the liftgate ajar input.
Outside air temperature HVAC module Input used to display the outside air temperature.
Odometer count PCM Input used for the odometer display. Input used by the IPC to calculate the Average Fuel Economy (AFE) and DTE.
Oil pressure warning indicator PCM Input used to control the oil pressure display, low oil pressure Reconfigurable Telltale (RTT) and to display the low oil pressure warning message.
PATS indicator command BCM Input used to display the PATS starting system fault message.
Parking aid audible warning indicator PAM Input used to display the check parking aid message for the rear parking aid.
Parking aid chime request PAM Input used to display the check front parking aid message.
Parking brake chime BCM Input used to display the parking brake engaged message.
Passenger door ajar BCM Input used to control the door ajar Reconfigurable Telltale (RTT) and warning message for the passenger door ajar input.
Passenger rear door ajar BCM Input used to control the door ajar Reconfigurable Telltale (RTT) and warning message for the RH rear door ajar.
PEPS system status BCM Input used to display the passive entry, push button start and key programming messages.
Perimeter alarm chime BCM Input used to display the vehicle alarm message.
Powertrain cooling message request PCM Input used to display the power reduced to lower engine temperature message.
Remote start status BCM Input used to display the instructional messages to the driver operating the vehicle once it is remote started.
Steering wheel message center switch commands SCCM Message center switch messages used to control the message center navigation and driver interaction.
Trailer brake status Trailer Brake Module (TBM) Input used to display the trailer brake system fault and general trailer brake electrical messages.
Trailer brake electrical status Trailer Brake Module (TBM) Input used to display the trailer lighting and electrical messages.
Trailer sway event in progress ABS module Input used to display the trailer sway reduce speed message.
Transmission fluid temperatrure PCM Input used for the transmission fluid temperature display.
Transmission gear display status PCM Input used for the SelectShift ® display.
Transmission gear position PCM Input used to display the PRNDL and PRNDL not in park message.
Transmission service required PCM Transmission input used to control the powertrain malfunction (wrench) Reconfigurable Telltale (RTT) and display the see manual message.
Transmission tow haul mode PCM Input used to control the tow haul Reconfigurable Telltale (RTT)
Vehicle mode BCM Input used to display the factory and transport mode messages. Input used to display the PRNDL not in park message.
Vehicle speed PCM Input used to display the PRNDL not in park message. Input used for the digital speedometer display. Input used to display the engine idle hours.

Network Message Chart - PCM 

Broadcast Message Originating Module Message Purpose
Wheel speed ABS module Input used by the PCM to calculate the vehicle speed.

Message Center Displays 

The message center switch (part of the LH steering wheel switch) is hardwired to the SCCM. The IPC receives the steering wheel message center switch message from the SCCM.

Compass Display 

The compass signal originates with the GPSM. The IPC receives the GPS direction from the BCM. There is no calibration or zone adjustment required since the compass heading is based on the GPS signal. For additional information on the GPSM, Refer to the appropriate article for the procedure.

Digital Speedometer Display (If Equipped) 

The IPC provides a redundant digital speedometer display in the message center. The digital speedometer display operates using the same vehicle speed inputs used to control the analog speedometer.

NOTE: There may be a difference between the speed indicated by the speedometer and the digital speedometer display due to the tolerances allowed for the speedometer indication.

The PCM calculates the vehicle speed from the wheel count message sent by the ABS module and from the tire size and axle ratio configuration in the PCM VID block. The PCM provides the IPC with a vehicle speed message to command the digital display.

DTE 

The DTE is calculated in the IPC using the Running Average Fuel Economy (RAFE), which is the fuel economy over the last 480 km (300 miles), and the fuel level input from the fuel sender(s) to determine how many miles the vehicle can be driven based on the remaining fuel in the tank. The DTE can vary in the short term by up to 50 miles, but is usually within 10 miles. Even if the fuel economy is relatively constant, the DTE can be off over a 50 mile range by -24% to +38%. The DTE display and the fuel gauge both use the fuel level input from the fuel tank to provide their respective functions. If the fuel gauge doesn't function correctly, both the fuel gauge and the DTE display are affected.

The IPC defaults to around 18 mpg when the battery is initially connected and changes based on driving habits and conditions. Generally, the driver should be getting somewhere between 13-21 mpg.

NOTE: The actual DTE can be higher or lower than the DTE displayed in the message center due to changes in driving conditions. It is important to understand how the DTE is calculated and the factors that impact the DTE display when determining how to address any DTE concerns.

Since the DTE is calculated and averaged over a longer period of time (480 km [300 miles]), varying driving conditions can have a significant impact on the current or short term DTE as opposed to the displayed DTE. This difference often leads to customer complaints of incorrect or invalid DTE. The following list provides some (not all) of the driving conditions that may lead to an incorrect or fluctuating DTE concern:

To better illustrate the affects of how driving conditions can affect DTE, refer to the following 2 examples. The first example below illustrates how the following observations are normal and expected since the low fuel reminder is triggered from a fuel volume and not from a fixed distance to empty.

The second example (below) illustrates what occurs when idling on an incline. In this example, the customer should be made aware of how the condition will correct after a few minutes of idling on a level surface.

Engine Hour And Engine Idle Hour Displays (If Equipped) 

The IPC provides engine hour and engine idle hour displays in the message center. The IPC receives the engine speed message for both displays from the PCM. The engine idle hour displays also uses vehicle speed to identify whether the engine is simply idling or if the vehicle is being driven. The IPC receives the vehicle speed message from the PCM.

Engine Oil Pressure (If Equipped) 

The engine oil pressure display provides a text-based display to supplement the low engine oil pressure warning indicator or Reconfigurable Telltale (RTT). The IPC receives the oil pressure warning indicator message from the PCM. Refer to the Owner's Literature for the message center menu navigation to display the engine oil pressure display.

Engine Oil Temperature (If Equipped) 

The engine oil temperature display provides a text-based engine oil temperature status to the driver. The IPC receives the engine oil temperature message from the PCM. Refer to the Owner's Literature for the message center menu navigation to display the engine oil temperature display.

Keypad Factory Code Display 

The message center can display the original keypad factory code when requested. The IPC receives the keycode status request from the BCM. Refer to Handles, Locks, Latches and Entry Systems Description and Operation (D&O) for the procedure to display the keypad factory code.

Off Road Display (If Equipped) 

The IPC provides a display screen in the message center to inform the customer of vehicle conditions such as vehicle roll and pitch when driving off road in rough terrain. The IPC uses multiple messaged inputs to control the following off road display components:

The IPC receives the hill descent message display, electronic stability control mode, vehicle roll and vehicle pitch messages from the ABS module.

The IPC receives the vehicle speed from the PCM and the 4x4 indicator message from the TCCM.

Oil Change Minder 

The message center provides an oil change minder to inform the driver an oil change is required. When the remaining oil life is between 1%-5%, the message center displays the change oil soon message. When the remaining oil life is at 0%, the message center displays the oil change required message. The duration of the interval between oil changes is calculated in the PCM and varies due to driving conditions. The PCM assumes a base mileage of 16, 090 km (10, 000 mi) or 1 year for normal driving. However, this number is adjusted down for conditions such as high engine temperature, high engine Revolutions Per Minute (RPM), use of flex fuel and low oil level (if equipped). The PCM calculates and provides an engine oil life percent message to the IPC.

When the oil is changed and the oil life is reset through the message center menu, the IPC sends the engine oil life reset request to the PCM.

Outside Air Temperature Display (If Equipped) 

The AAT sensor is hardwired to the PCM through separate input and return circuits. The PCM provides a reference voltage to the AAT sensor and monitors the change in voltage resulting from changes in resistance as determined by outside air temperature. The PCM messages the outside air temperature data to the HVAC module through the BCM. The HVAC module filters the temperature data and sends the updated outside air temperature data back to the BCM. The BCM in turn messages the outside air temperature in degrees Celsius (metric) to the IPC. When the Fahrenheit (English) display is selected by the driver, the IPC converts the Celsius to Fahrenheit and displays the temperature in the message center.

NOTE: The outside air temperature is only displayed in the base IPC.

The HVAC module is programmed to update the messaged outside air temperature data at different rates depending on several criteria to prevent false temperature displays due to a condition known as heat soaking. Heat soaking is where the outside air temperature is hotter in the location of the AAT sensor than the actual outside air temperature.

When the sensed outside temperature rises, the display updates slowly at varying rates based on vehicle speed. When the sensed outside temperature drops, the display updates more quickly following the drop experienced by the AAT sensor.

PRNDL/Progressive Range Select And SelectShift ® Displays 

The IPC receives the transmission gear position message from the PCM. The IPC also uses a park detect switch (part of the selector lever) input to signal the IPC the shift lever is fully seated in the PARK (P) position. The IPC compares the park detect switch input with the park status in the transmission gear position message sent from the PCM. The IPC provides a battery reference voltage to the park detect switch. When the selector lever is in PARK (P), the park detect switch routes the reference voltage to ground, pulling the circuit low to the IPC. When the selector lever is moved out of PARK (P), the park detect switch opens to ground, sending the reference voltage high.

The progressive range select display provides a numerical display of the lower transmission ranges and indicates to the driver which gear is currently selected when the driver has manually shifted to a lower range (1, 2, 3, 4, 5 or 6). The IPC receives the transmission gear display status message from the PCM.

The SelectShift ® display indicates to the driver which gear is currently selected when the transmission is in the SelectShift ® mode. The IPC receives the transmission gear display status message from the PCM. When the transmission is in SelectShift ® mode, the gear number is displayed in the SelectShift ® display area.

For additional information related to the progressive range select or SelectShift ® features, refer to the Owner's Literature.

Transmission Temperature (If Equipped) 

The IPC provides a text-based transmission fluid temperature display to indicate the transmission operating temperature. The IPC receives the transmission fluid temperature message from the PCM. The PCM filters the transmission fluid temperature signal to remove fluctuations that would affect the transmission temperature display. Refer to the Owner's Literature for the message center menu navigation to display the transmission fluid temperature display.

Message Center Messages 

Adaptive Headlamps 

The IPC provides a message to inform the driver an adaptive headlamps concern exists. The IPC receives the adaptive headlamp fault message from the HCM.

BLIS ® /CTA System (If Equipped) 

The IPC provides warning messages to indicate a fault condition in the /CTA system and warning messages to indicate a CTA vehicle approach. The IPC receives the BLIS ® side detection sensor status message and the CTA message from the BCM.

Brake System 

The IPC provides brake system displays for low brake fluid level, parking brake applied and ABS concerns that display along with the brake warning indicator operation. When the parking brake is applied, the BCM sends the parking brake chime message to the IPC to illuminate the brake warning indicator and display the parking brake applied message in the message center.

When a low brake fluid level condition exists, the BCM sends the brake fluid level low indicator message to the IPC to illuminate the brake warning indicator and display the brake fluid level low message in the message center.

When an ABS concern exists, the ABS module sends the brake lamp request message to the IPC to illuminate the brake warning indicator, and to display the brake system fault message in the message center.

Charging System Fault Warning 

The IPC receives the battery charge low message from the BCM. When a fault is detected in the charging system, the BCM sends the IPC the battery charge low message to illuminate the charging system warning indicator and the charging system fault warning message.

Check Fuel Fill Inlet 

The PCM monitors the fuel tank evaporative emission system for significant leaks that occur following refueling of the vehicle. Once the PCM detects a fuel vapor leak, the PCM sends a fuel fill inlet indication message to the IPC to display the check fuel fill inlet message.

Engine Over-Temperature Warning 

The IPC provides an engine over-temperature warning message in combination with the engine temperature gauge to alert the driver of an engine over-temperature condition. The PCM uses the CHT sensor to measure the engine temperature. The IPC receives the engine coolant temperature message from the PCM. When the PCM detects an engine over-temperature condition, the PCM sends the IPC the engine coolant temperature message to send the engine temperature gauge to full hot, illuminate the engine temperature warning indicator or Reconfigurable Telltale (RTT) and display the engine coolant over-temperature message center message.

Hill Descent Control 

When the hill descent control is active, the IPC provides message center messages to alert the driver of the various hill descent system states. The IPC receives the hill descent message display message from the ABS module.

Load Shed 

The IPC provides messages to inform the driver of the battery state of charge and to turn off accessories to reduce the load on the battery or the system automatically reduces the load by turning off accessories. The IPC receives the battery charge low message from the BCM.

Low Oil Pressure Warning 

The engine oil pressure switch is hardwired to the PCM. When the engine oil pressure is low, the PCM provides the oil pressure warning indicator request to the IPC to illuminate the low oil pressure warning indicator or Reconfigurable Telltale (RTT) and to display the low engine oil pressure warning message.

Neutral Tow 

The IPC provides towing system messages to indicate the status of the neutral tow feature. When the neutral tow system is enabled and the vehicle is capable of free-rolling, the IPC receives a 4x4 status indication message from the TCCM to display the applicable neutral tow status messages.

Parking Aid System 

The IPC provides messages to indicate the status of the parking aid system. When a fault condition exists in the parking aid system, the PAM sends the parking aid audible warning indicator message or parking aid chime request message to the IPC to display the check rear or front park aid message.

PATS, IKT, Passive Key And Immobilizer Messages (If Equipped) 

The IPC provides the IKT, passive key and immobilizer system message center messages to inform the driver the IKT key could not be programmed, key detect status, accessory power is active, to inform the driver to press the brake to start the vehicle or to restart the vehicle or a key will be needed. The IPC uses the PEPS system status message from the BCM to display the passive key and immobilizer message center messages.

The IPC also provides a message to inform the driver of a starting system concern related to the PATS. The IPC uses the PATS indicator command message from the BCM to display the PATS message center message.

Perimeter Alarm 

The IPC provides a display to indicate the perimeter alarm has been activated and to start the vehicle to stop the alarm. The IPC receives the perimeter alarm chime request message from the BCM.

Powertrain Cooling Warning 

On vehicles equipped with a GTDI engine, the IPC provides a message to inform the driver that vehicle performance is reduced to allow the engine to cool. This feature is part of the smart cooling function in the PCM and provides powertrain cooling protection under high ambient temperature conditions. The IPC receives the powertrain cooling message request from the PCM.

Powertrain Malfunction (Wrench) 

The IPC receives the engine service required and the transmission service required messages from the PCM. The IPC receives the 4x4 range fault message from the TCCM.

When a fault condition exists in any of the monitored systems, the IPC illuminates the powertrain malfunction indicator or Reconfigurable Telltale (RTT) and displays the see manual message for an engine-transmission concern or displays the check 4x4 message.

PRNDL Not In Park 

The Instrument Panel Cluster (IPC) provides a shift to park message to inform the driver the vehicle is not in PARK (P) under 2 sets of conditions. First, the Instrument Panel Cluster (IPC) displays the shift to park message if the vehicle is not in PARK (P), the ignition is OFF and the driver door is open or ajar. Second, the Instrument Panel Cluster (IPC) displays the shift to park message if the vehicle is not in PARK (P), the ignition is ON or in ACT, the driver door is open or ajar and the brake pedal is not applied with vehicle speed less than 5 km/h. (3 mph).

The Instrument Panel Cluster (IPC) uses the transmission gear position and vehicle speed messages sent from the PCM and the ignition status, driver door ajar status and the vehicle mode messages sent from the BCM to display the transmission not in park message center message.

Remote Start 

The IPC provides messages to indicate to the driver actions required to drive the vehicle after a remote start. The IPC receives the remote start status message from the BCM.

Stability-Traction Control 

The Instrument Panel Cluster (IPC) provides a stability-traction control system message center message to indicate the stability-traction control system has a fault and requires service. When a fault condition exists in the stability-traction control system, the ABS module sets a DTC and sends the brake chime request message to the Instrument Panel Cluster (IPC) to display the service AdvanceTrac ® message center message.

Steering System 

The IPC provides message center messages to indicate there is an EPAS system concern. When a fault exists in the EPAS, the PSCM sends EPAS fault message to the IPC to display the applicable steering system fault message.

Trailer 

The IPC provides message center messages to inform the driver of conditions related to the Trailer Brake Module (TBM), trailer brakes, trailer charging, trailer wiring and trailer lighting. The IPC also provides a warning message to inform the driver the flashing stability-traction control is the result of a trailer sway condition and to reduce vehicle speed.

The IPC receives the trailer brake electrical status message from the BCM, the trailer brake status message from the Trailer Brake Module (TBM) and the trailer sway event in progress message from the ABS module.

Reconfigurable Telltale (RTT) Indicators 

4WD (2WD, 4X4 L, 4X4 H, 4X4 A And 2 H) 

The IPC receives the 4WD status from the TCCM. If the vehicle is shifted into 2WD, 4WD auto or 4WD low or high, the TCCM sends the IPC the 2WD, 4x4 auto, 4x4 high or 4x4 low message to illuminate the applicable Reconfigurable Telltale (RTT).

Charging System 

The charging system Reconfigurable Telltale (RTT) is controlled by the IPC based upon data received from the BCM. The BCM receives the battery charge low message from the PCM. When a fault is detected in the charging system, the BCM sends the IPC the battery charge low message to illuminate the charging system Reconfigurable Telltale (RTT). Refer to Charging System for additional information on the charging system operation.

Cruise Control 

The IPC receives the cruise control status display and cruise control set speed display messages from the PCM.

When the cruise control switch is placed in the ON position, the PCM sends the IPC a standby mode request through the cruise control status display message and the IPC illuminates the cruise control indicator in gray. When the cruise control is engaged, the IPC changes the cruise control indicator illumination from gray to green and the set speed is displayed in the set speed display area.

Door And Liftgate Ajar 

The IPC receives the door ajar status for the LF, RF, LR, RR and the liftgate ajar switches from the BCM. When the IPC receives a driver door, passenger door, left rear door, passenger rear door or liftgate ajar status message from the BCM that one or more doors are open or ajar, the IPC illuminates the appropriate door ajar Reconfigurable Telltale (RTT).

Engine Over-Temperature 

The PCM uses the CHT sensor to measure the engine temperature. The IPC receives the engine coolant temperature data message from the PCM. The IPC requires 2 basic messaged inputs to control the engine over-temperature Reconfigurable Telltale (RTT). The first is the engine coolant temperature data message. The second is an engine overheat mitigation message. When the PCM sends the engine coolant temperature data or engine overheat mitigation message, the IPC illuminates the engine over-temperature Reconfigurable Telltale (RTT).

Hill Descent Control 

The hill descent control system maintains vehicle speed on a downhill grade at operating speeds between 3.2 km/h (2 mph) and 32.2 km/h (20 mph). The system goes into standby mode on a flat or uphill terrain. The system deactivates at speeds above 64.4 km/h (40 mph). During periods of sustained use, the hill descent control system may automatically deactivate in order to cool the braking system.

When the hill descent control is engaged, the PCM then sends a message to the ABS module requesting system activation. The ABS module uses inputs from the RCM and wheel speed sensors to determine the mode of operation.

The IPC receives the hill descent message display message from the ABS module. The message center also displays hill descent control messages to inform the driver they have entered or exited various states of the hill descent control function.

Low Fuel 

The IPC uses fuel level, running average fuel economy, odometer counts and fuel flow data to calculate the DTE. The low fuel Reconfigurable Telltale (RTT) is controlled using the calculated DTE. When the DTE display is 120 km (75 miles) (with a MyKey ® programmed key) or 80 km (50 miles) (with an administrator key) to empty or less, the IPC illuminates the low fuel Reconfigurable Telltale (RTT).

Low Oil Pressure 

The engine oil pressure switch is hardwired to the PCM. The PCM sends the engine speed and oil pressure warning indicator messages to the IPC. The IPC requires engine Revolutions Per Minute (RPM) above 400 Revolutions Per Minute (RPM) before the message center displays the low oil pressure Reconfigurable Telltale (RTT).

The PCM provides a reference voltage to the engine oil pressure switch when the ignition is in RUN. With the engine running and low or no oil pressure, the engine oil pressure switch remains open. The PCM detects no change in the reference voltage and provides the IPC a request to illuminate the low oil pressure warning indicator. With the engine running and sufficient oil pressure, the engine oil pressure switch closes, pulling the reference voltage low. The PCM detects the low reference voltage and provides the IPC a request to turn off the low oil pressure warning indicator.

The engine oil pressure switch is hardwired to the PCM. The IPC receives the oil pressure warning message and the engine Revolutions Per Minute (RPM) message from the PCM. With the KOEO, the IPC does not display the low oil pressure Reconfigurable Telltale (RTT) until the engine is started and it receives the engine Revolutions Per Minute (RPM) message.

Low Washer Fluid 

The low washer fluid level sensor is hardwired to the IPC through a single signal circuit. The low washer fluid sensor is grounded through a separate ground circuit. The IPC provides a battery reference voltage to the washer fluid level switch. When the washer fluid is low, the washer fluid level switch closes to ground, pulling the reference voltage low. When the IPC detects the washer fluid input pulled low, it illuminates the low washer fluid level Reconfigurable Telltale (RTT).

Powertrain Malfunction (Wrench) 

The IPC receives the engine service required and the transmission service required messages from the PCM and the 4x4 range fault message from the TCCM.

When a fault condition exists in the ETC system, the PCM provides the IPC with the engine service required message to illuminate the powertrain malfunction (wrench) Reconfigurable Telltale (RTT).

When a fault condition exists in the transmission, the PCM provides the IPC with the transmission service required message to illuminate the powertrain malfunction (wrench) Reconfigurable Telltale (RTT).

When a fault condition exists in the 4WD system, the PCM provides the IPC with the 4x4 range fault message to illuminate the powertrain malfunction (wrench) Reconfigurable Telltale (RTT).

Tow Haul 

The tow haul Reconfigurable Telltale (RTT) illuminates when the tow haul system has been engaged and is actively providing tow haul control for the vehicle. When the vehicle is actively providing tow haul control, the PCM sends the transmission tow haul mode message to the IPC to illuminate the tow haul Reconfigurable Telltale (RTT).

Component Description 

Brake Fluid Level Switch 

The brake fluid level switch is mounted in the master cylinder reservoir and is hardwired to the BCM through separate signal and return circuits and is grounded to a body ground through a separate circuit. The BCM provides a battery reference voltage to the brake fluid level switch. When the brake fluid level is low, the float drops closing the switch, pulling the reference voltage low. When the brake fluid level is high, the float lifts, releasing the switch contacts and removing the ground to the BCM.

Fuel Level Sender 

The fuel level sender is mounted to the fuel pump assembly. The fuel level sender is a dual sweep potentiometer style resistor connected to a float mechanism. The dual sweep design provides a second resistance measurement that reduces the intermittent loss of data due to corrosion between the resistor wires and the sweep arm. As the fuel level changes, the float rises or falls with the fuel level moving the sweep arm across the resistor wires. This movement either increases or decreases the resistance through the unit. The fuel level sender resistance ranges from 180 ohms ± 4 ohms at empty (E) to 10 ohms ± 2 ohms at full (F). When the fuel level is low, the fuel level sender resistance is high. When the fuel level is high, the fuel level sender resistance is low.

The fuel pump assembly is hardwired to the IPC through separate signal and return circuits. The fuel level return circuit is grounded internally in the IPC. The IPC provides a battery reference voltage on the fuel level signal circuit. As the fuel level changes, the change in resistance raises or lowers the fuel level signal voltage depending on the resistance of the fuel level sender.

Parking Brake Position Switch 

The parking brake position switch is hardwired to the BCM through a single signal circuit and grounded through a separate ground circuit. The BCM provides a battery reference voltage on the signal circuit. When the parking brake is not applied, the parking brake position switch is open. When the parking brake is applied, the parking brake position switch closes, pulling the reference voltage low.

Steering Wheel Switch - Message Center 

The message center switch portion of the LH steering wheel switch is comprised of 5 buttons. Each button operates a unique switch within the overall switch assembly with each button using a different resistance value. The SCCM sends out a reference voltage to the LH steering wheel switch on the input circuit and monitors the voltage drop when a message center switch button is pressed. The voltage drop varies depending upon the resistance of the specific button pressed, indicating to the SCCM which switch is pressed.

Low Washer Fluid Level Switch 

The low washer fluid level switch is mounted in the washer fluid reservoir and is hardwired to the IPC through a single signal wire. The low washer fluid level switch is grounded to a body ground through a separate circuit. The IPC provides a battery reference voltage to the low washer fluid level switch. When the washer fluid level is low, the float drops closing the switch and pulling the reference voltage low. When the washer fluid level is high, the float lifts off the switch and opens the circuit to the IPC sending the reference voltage high.

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