U1403

SYMPTOM
U1403 - IMPLAUSIBLE FUEL LEVEL SIGNAL

WHEN MONITORED
Ignition on.

SET CONDITION
The fuel level message the PCM is receiving is implausible. The circuit is continuously monitored.

POSSIBLE CAUSES
- CAN B OPEN OR SHORTED
- CLUSTER MODULE
- FRONT CONTROL MODULE
- PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Scan Tool Testing and Procedures

THEORY OF OPERATION
The Front Control Module isn't receiving a fuel level signal over CAN B from the Cluster Module. The FCM has to send the PCM a fuel level signal over CAN C. The signal the FCM sends over CAN C is implausible.

DIAGNOSTIC TEST
1. ACTIVE DTC





Ignition on, engine not running.
With a scan tool read DTCs.
Is the DTC active at this time?
Yes>> Go To 2
No>> Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5. Powertrain Verification Test - Ver 5

2. CAN B BUS HARDWARE DTCS ALSO ACTIVE





With a scan tool check for DTCs in the FCM.
Are any CAN B Hardware related DTCs active at this time?
Yes>> Perform BODY VERIFICATION TEST VER-1.
No>> Replace and program the Powertrain Control Module per Service Information. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.