Test A: Incorrect Fuel Gauge Indication

PINPOINT TEST A: INCORRECT FUEL GAUGE INDICATION

A1:

A2-A4:

A5-A7:

A7-A9:

A9-A10:

A10-A11:

A12-A13:

A13-A14:

A15-A18:

A19-A20:

A20-A22:

NOTE:
- The fuel pump module may also be called the fuel tank unit.
- The remote fuel sender may also be called the fuel sender or fuel level sensor.

Normal Operation
The fuel tank is a saddle tank design with variable resistance senders in each side of the tank. The fuel pump module and the remote fuel sender are driven by floats that provide resistances related to the fuel level on each side of the tank to the smart junction box (SJB). The fuel pump module and the remote fuel sender uses an approximate resistance range between 15 ohms ± 2 ohms at empty (E) and 160 ohms ± 4 ohms at full (F). The fuel pump module is hardwired to the SJB through the signal circuit 1356 (LG/VT) and the return circuit 1357 (LB/YE). The remote fuel sender is hardwired to the SJB through the signal circuit 29 (YE/WH) and the return circuit 1357 (LB/YE). The SJB monitors the resistance readings that are sent to the SJB from the fuel pump module and the remote fuel sender and sends the instrument cluster a message over the communication network to command the fuel gauge with a corresponding movement of the pointer. If the remote fuel sender is open, the fuel gauge defaults to the fuel pump sender value only and the fuel gauge indicates E to 1/2 tank. If the fuel pump sender is open, the fuel gauge defaults to the empty position.

NOTE: For system testing during the pinpoint test, make sure to use only the SJB self-test and SJB DTCs B1201, B1202, B2627 and B2628. Once the repairs are complete, clear the SJB and instrument cluster DTCs.

The only the instrument cluster DTC used for diagnosis is B2879.

DTC B1201 - sets in the SJB on-demand if the SJB detects a short to ground on the input from circuit 1356 (LG/VT) or if circuit 1356 (LG/VT) is shorted to circuit 1357 (LB/YE).

DTC B1202 - sets in the SJB on-demand if the SJB detects an open or short to voltage on the input from circuits 1356 (LG/VT) or 1357 (LB/YE).

DTC B2627 - sets in the SJB on-demand if the SJB detects an open or short to voltage on the input from circuits 29 (YE/WH) or 1357 (LB/YE).

DTC B2628 - sets in the SJB on-demand if the SJB detects a short to ground on the input from circuit 29 (YE/WH) or if circuit 29 (YE/WH) is shorted to circuit 1357 (LB/YE).

DTC B1202 - is a continuous DTC set in the instrument cluster if the message from the SJB indicates an open or short to voltage on the input from circuits 1356 (LG/VT) or 1357 (LB/YE) for 33 seconds.

DTC B1204 - is a continuous DTC set in the instrument cluster if the message from the SJB indicates a short to ground on the input from circuit 1356 (LG/VT) or if circuit 1356 (LG/VT) is shorted to circuit 1357 (LB/YE) for 33 seconds.

DTC B2627 - is a continuous DTC set in the instrument cluster if the message from the SJB indicates an open or short to voltage on the input from circuits 29 (YE/WH) or 1357 (LB/YE).

DTC B2628 - is a continuous DTC set in the instrument cluster if the message from the SJB indicates a short to ground on the input from circuit 29 (YE/WH) or if circuit 29 (YE/WH) is shorted to circuit 1357 (LB/YE).

NOTE: Normal operation of the fuel delivery system allows the remote side of the fuel tank (the side opposite the fuel filler hose inlet) to have less fuel than the fuel pump module side of the tank (the side with the fuel filler hose inlet).

DTC B2879 - is a continuous DTC set in the instrument cluster if the fuel level message from the SJB indicates a large discrepancy in the amount of fuel between the fuel pump module and the remote fuel sender sides of the tank. The fuel level in the remote fuel sender side of the tank (the side opposite the fuel filler hose inlet) has significantly more fuel than the fuel pump module side of the tank (the side with the fuel filler hose inlet).

Possible Causes
- Circuit 29 (YE/WH) short to circuit 1357 (LB/YE)
- Circuit 29 (YE/WH) open, short to ground or voltage
- Circuit 1356 (LG/VT) open, short to ground or voltage
- Circuit 1356 (LG/VT) short to circuit 1357 (LB/YE)
- Circuit 1357 (LB/YE) open or voltage
- Fuel pump module
- Remote fuel sender
- SJB
- Fuel tank
- Instrument cluster