System Operation: Gauges

Fuel Gauge 

The IPC sends a reference voltage to the fuel level sender. As the fuel level changes, a float actuates the variable resistor fuel level sender, raising or lowering the fuel level signal voltage. The IPC monitors the changes in voltage from both senders and commands the fuel gauge with a corresponding movement of the pointer.

The IPC interprets the fuel level input and uses 4 different operating modes to calculate the fuel level:

• Anti-slosh (default mode)
• Key OFF fueling
• Key ON fueling
• Recovery

After a fuel fill up, the time for the fuel gauge to move from empty (E) to full (F) ranges from 2 seconds to 55 minutes depending on which operating mode the fuel gauge is in.

Anti-Slosh Mode 

The default fuel gauge mode is called the anti-slosh mode. To prevent fuel gauge changes from fuel slosh (gauge instability due to changes in fuel sensor readings caused by fuel moving around in the tank), the fuel gauge takes approximately 55 minutes to go from empty (E) to full (F).

Key OFF Fueling Mode 

The key OFF fueling mode (2 seconds to read empty [E] to full [F]) requires the following conditions be met:

• The ignition must be OFF when refueling the vehicle.
• At least 15% of the vehicle's fuel capacity must be added to the fuel tank.
• The IPC must receive a valid key ON fuel sensor reading within one second of the ignition being put into RUN. The key ON sample readings are considered valid if the fuel sensor reading is between 10 ohms ± 2 ohms and 180 ohms ± 4 ohms.

If these conditions are not met, the fuel gauge stays in the anti-slosh mode, which results in a slow to read full (F) event.

Key ON Fueling Mode 

The key ON fueling mode (approximately 60 seconds to read empty [E] to full [F]) requires the following conditions be met:

• The transmission is in PARK or NEUTRAL.
• The ignition is in RUN.
• At least 15% of the vehicle's fuel capacity must be added to the fuel tank.

In key ON fueling mode, a 30 second timer activates after the transmission is put into the PARK or NEUTRAL position. When the 30 second time has elapsed and at least 15% of the vehicle's fuel capacity has been added, the fuel gauge response time is 60 seconds to read from empty (E) to full (F). When the transmission is shifted out of PARK or NEUTRAL, the fuel gauge strategy reverts to the anti-slosh mode. The key ON fueling mode prevents slow to read full events from happening if the customer refuels the vehicle with the ignition in RUN.

Recovery Mode 

Recovery mode is incorporated into the IPC strategy to recover from a missing fuel level input after a refueling event. Missing fuel level inputs result from intermittent opens in the fuel sensor or its circuits. Recovery mode (empty [E] to full [F] in approximately 20 minutes) is initiated when the following conditions are met:

• The IPC is in the anti-slosh (default) mode.
• The actual fuel level in the tank is greater than what is being displayed by the fuel gauge.

Odometer 

The IPC receives the odometer count message from the PCM. The IPC monitors the odometer count input from the PCM and commands the odometer with a digital display in the message center.

Power Distribution Gauge (Base And Mid-Level IPC Only) 

The power distribution gauge displays the level of torque applied to the front and rear wheels. The power distribution system is always active, it is transferring torque whenever the vehicle is accelerating, boosting output when wheels are slipping and shutting off on the highway to save fuel.

The IPC uses the following messaged inputs to determine the power distribution gauge display: Wheel torque data

• 4x4 range fault
• 4x4 range selection
• Gear lever position
• Vehicle speed
• Wheel torque

As power is applied to the wheels, the area directly in front (front wheels) or rear (rear wheels) of each displayed wheel begins to fill in. The lowest power displayed is the closest to the wheel. As the amount of power sent to the wheels increases, the area fills in either forward (front wheels) or rearward (rear wheels) of the wheels. The IPC receives the 4x4 range fault and 4x4 range selection messages from the TCCM over the HS-CAN. The IPC receives the gear lever position, vehicle speed and wheel torque from the PCM over the HS-CAN.

Speedometer 

The PCM calculates the vehicle speed from the wheel count message received from 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 speedometer pointer.

The IPC provides a tolerance which allows the gauge to display between 3% lower and 7% higher than the actual vehicle speed. This means that with an actual vehicle speed of 96.6 km/h (60 mph), the speedometer may indicate between 93.7 km/h (58.2 mph) and 103.3 km/h (64.2 mph), which is normal.

Tachometer 

The base, mid-level and optional IPC tachometers appear differently but function the same. The base and mid-level IPC uses an analog gauge. The optional IPC uses a virtual gauge (video image) that provides a 6, 000 Revolutions Per Minute (RPM) bar graph or a simulated 7, 000 Revolutions Per Minute (RPM) gauge display depending on the selected display mode.

The PCM uses the CKP sensor to measure the engine Revolutions Per Minute (RPM). The IPC receives the engine speed message from the PCM.

Temperature Gauge 

The temperature gauge is an analog gauge in the base and mid-level IPC. The temperature gauge is a virtual gauge (video image) on the high-level IPC and is located in the LH LCD display area.

The PCM uses the CHT sensor to measure the engine temperature. The IPC receives the engine coolant temperature message from the PCM.