Gauges - Analog Or Virtual

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 the fuel level sender and sends a fuel level data message to the PCM through the GWM to calculate the fuel level.

The PCM calculates the fuel level based on current fuel in the fuel tank and the tank size. The PCM sends the fuel level display message to the IPC through the GWM to activate the needle in the fuel gauge.

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

The PCM uses 4 different operating modes to calculate the fuel level:

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

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 40 minutes to go from empty (E) to full (F).

The key off fueling mode (2 seconds to read empty [E] to full [F]) requires 3 conditions to be met:

• The ignition must be in the OFF mode when refueling the vehicle.
• At least 10% of the vehicle's fuel capacity must be added to the fuel tank.
• The IPC must receive a valid ignition ON fuel sensor reading within one second of the ignition being put into the RUN mode. 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.

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 P or N.
• The ignition is in the RUN mode.
• At least 10% 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 P or N position. When the 30-second time has elapsed and at least 9% 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 P or N, 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 the RUN mode.

Speedometer 

The IPC receives the vehicle speed data from the PCM. The PCM receives the wheel speed data from the ABS. The PCM uses axle ratio and tire size stored in the vehicle configuration file along with wheel speed inputs to generate a vehicle speed signal.

The IPC provides a tolerance that allows the speed indication to display between 3% below and 7% above the actual vehicle speed. This means that with an actual vehicle speed of 97 km/h (60 mph), the speedometer can indicate between 94-103 km/h (58-64 mph). Incorrect tire size or tire size configuration could potentially affect the speedometer accuracy.

Tachometer 

The IPC uses engine rpm data from the PCM to display the current rpm in the gauge.

Temperature Gauge 

The IPC uses 2 messages to control the temperature gauge. The first is the engine coolant temperature data, which provides the current engine temperature input to the PCM. The second message is the engine overheat indication request, which is sent by the PCM to the IPC when an overheating condition exists. When the IPC receives the engine overheat indication request message, the IPC sends the temperature gauge to full hot and turns on the over-temperature warning indicator.