Test B: Incorrect Fuel Gauge Indication

PINPOINT TEST B: INCORRECT FUEL GAUGE INDICATION

Normal Operation
The fuel pump module is hardwired to the instrument cluster (IC) through the input circuit VMC11 (YE/VT) and return circuit RMC32 (GN/BU). The fuel level sensor (part of the pump module) is a variable resistor actuated by a float with resistance ranging between 180 ohms ± 4 ohms at empty (E) to 10 ohms ± 2 ohms at full (F). The instrument cluster (IC) provides a reference voltage to the fuel pump module on the input circuit. As the fuel level changes, the fuel level sensor float moves up or down according to the fuel level altering the fuel level signal voltage through the resistor. The instrument cluster (IC) interprets this signal and commands the fuel gauge pointer to sweep to the correct level.

The instrument cluster (IC) 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.

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 sender readings caused by fuel moving around in the tank), the fuel gauge takes approximately 55 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 be met:
- The key must be in the OFF position throughout the entire refueling of the vehicle.
- At least 15% of the vehicle's fuel capacity must be added to the fuel tank.
- The instrument cluster (IC) must receive a valid key ON fuel sender reading within 1 second of the key being put into the RUN position. The key ON sample readings are considered valid if the fuel sender 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 90 seconds to read empty [E] to full [F]) requires 3 conditions be met:
- The transmission is in PARK (P).
- The key is in the RUN position.
- 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 (P) 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 90 seconds to read from empty (E) to full (F). When the transmission is shifted out of PARK (P), 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 key in the RUN position.

Recovery mode is incorporated into the instrument cluster (IC) strategy to recover from a missing fuel level input after a refueling event. Missing fuel level inputs result from intermittent opens in the fuel sender or its circuits. Recovery mode (empty [E] to full [F] approximately 20 minutes) is initiated when the following 2 conditions are met:
- The instrument cluster (IC) 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.

Instrument Cluster (IC) DTCs
- DTC B1203 (Fuel Sender Circuit Short to Battery) - is a continuous and on-demand DTC that sets if the instrument cluster (IC) detects an open or short to voltage on the input circuit VMC11 (YE/VT) for more than 33 seconds.
- DTC B1204 (Fuel Sender Circuit Short to Ground) - is a continuous and on-demand DTC that sets if the instrument cluster (IC) detects a short to ground on the input circuit VMC11 (YE/VT) or a short together between the input circuit VMC11 (YE/VT) and the return circuit RMC32 (BN/BU) for more than 33 seconds.

PCM DTCs:

This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Fuel level sensor
- Fuel pump module assembly
- Fuel tank
- Instrument cluster (IC)

B1-B3:

B3-B5:

B5-B8:

B8-B10:

B10-B12:

B12-B13: