Test B: Incorrect Fuel Gauge Indication

PINPOINT TEST B: INCORRECT FUEL GAUGE INDICATION

B1-B3:

B3-B6:

B6-B9:

B10-B12:

B13:

Normal Operation
The fuel tank is a saddle tank design with variable resistance senders, driven by floats, that provide resistances related to fuel height, to the smart junction box (SJB). The fuel level is determined using a variable resistance fuel sender unit, with an approximate resistance range between 15 ohms at empty (E) and 160 ohms at full (F) ± 1%. The fuel pump sender 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 senders 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.

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