Fuel Pump: Description and Operation

Fuel Pumps

Primary Fuel Pump - No Commands Received
The rear electronics module drives the fuel pump motor. It also monitors the circuit and sends its status to the ECM via the communications network buses. As part of this status, the ECM receives flags indicating invalid input and open circuit on the battery supply. If either of these flags indicates a fault for longer than a set time, then a fault judgment is made and P1234 is logged.

Primary Fuel Pump - Not Working When Requested
The ECM also receives a 'fuel pump loss of ground' flag via the CAN network from the rear electronics module. If this flag is set for longer than a pre-defined time a fault judgment is made and P1236 is logged.

Primary Fuel Pump Circuit High/Low Fault
The ECM also receives the following flag via the CAN bus from the rear electronics module:
- Fuel pump monitor line open circuit.
- Fuel pump monitor line short circuit to battery.
- Fuel pump monitor line short circuit to ground

If any of these flags indicate a fault for longer than a set time, then a fault is registered and P1338 is logged.













Secondary Fuel Pump Monitor
A status flag monitors the Pulse Width Modulation (PWM) signal from the secondary fuel pump driver module. When this status flag is stuck low for a set time, then a fault is flagged and P1233 is logged. When this status flag is stuck high, or the PWM duty is outside a calibrated range for a set time, then a fault is flagged and P1339 is logged.