Test B: Incorrect Fuel Gauge Indication

PINPOINT TEST B: INCORRECT FUEL GAUGE INDICATION

B1-B3:

B3-B4:

B4-B5:

B5-B7:

B8-B9:

B9-B11:

B11-B13:

B13-B14:

Normal Operation
The instrument cluster is hardwired to the fuel sending unit, which is a variable resistor controlled by the action of a float arm. The fuel gauge receives its signal from the fuel level sensor, part of the fuel pump module. The fuel level is determined using a variable resistance fuel level sender unit, with an approximate resistance range between 138 ohms ± 4 ohms when full (F) and 7 ohms ± 2 ohms at empty (E) for vehicles equipped with flex-fuel and 160 ohms ± 4 ohms at full (F) and 15 ohms ± 2 ohms at empty (E) for vehicles not equipped with flex-fuel. The fuel level sender unit is hardwired to the instrument cluster through the signal circuit 29 (YE/WH) and the return circuit 396 (BK/OG). The instrument cluster monitors the resistance readings that are sent to the instrument cluster from the fuel pump module and commands the fuel gauge with a corresponding movement of the pointer. This information is also supplied by the instrument cluster to the powertrain control module (PCM) through the communication network.

On flex-fuel vehicles, basic fuel level indication is the same as gasoline vehicles, except that the flex-fuel vehicles incorporate the use of a flex-fuel module and converter harness. The flex-fuel module and converter harness is a DC-AC-DC interface, used to prevent chemical reactions created by the interaction of DC current with the fuel. The flex-fuel module and converter harness is part of the wire jumper harness between the vehicle wiring harness and the fuel pump module and is installed as an assembly. The flex-fuel module and converter harness receives voltage on circuit 705 (LG/OG) and is grounded through the fuel pump motor ground, circuit 57 (BK)

DTC B1201 - is a continuous and on-demand DTC that sets if the instrument cluster detects an open or short to voltage for greater than 33 seconds on the fuel level input, circuit 29 (YE/WH).

DTC B1204 - is a continuous and on-demand DTC that sets if the instrument cluster detects a short to ground for greater than 33 seconds on the fuel level input, circuit 29 (YE/WH) or if circuits 29 (YE/WH) and 396 (BK/OG) are shorted together.

Possible Causes
- Fuse
- Circuit 29 (YE/WH) open, short to ground or voltage
- Circuits 29 (YE/WH) and 396 (BK/OG) shorted together
- Circuit 396 (BK/OG) open or short to voltage
- Circuit 705 (LG/OG) open (flex-fuel only)
- Fuel pump module assembly
- Flex-fuel module and converter wire harness (if equipped)
- Fuel tank
- Fuel level sensor
- Instrument cluster