DTC P0463: Fuel Level Signal High: Testing

1. If Instrument Panel Cluster (IPC) system diagnostic system check has been performed, go to next step. If IPC system diagnostic system check has not been performed, perform IPC system diagnostic system check. See INSTRUMENT PANEL CLUSTER DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
2. Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). DLC is located below left side of instrument panel, to right of steering column. Turn ignition on, with engine off. Using scan tool, observe FUEL LEVEL parameter in PCM EVAP data list. If scan tool displays more than 5.0 volts, go to next step. If scan tool displays less than 5.0 volts, go to DIAGNOSTIC AIDS  .
3. Turn ignition switch to OFF position. Disconnect fuel level sender harness connector. Connect a 3-amp fused jumper wire between fuel level sender harness connector Black wire and Purple wire terminals. Turn ignition on, with engine off. Using scan tool, observe FUEL LEVEL parameter in PCM EVAP data list. If scan tool does not display less than .39 volts, go to next step. If scan tool displays less than .39 volts, go to step  6 .
4. Test Purple wire between fuel sender harness connector and Powertrain Control Module (PCM) Red harness connector C2 terminal No. 54 for open circuit or high resistance or short to voltage. See Figure . PCM is located in front left corner of engine compartment, inside air cleaner. If problem is not found, go to next step. If problem is found, repair as necessary. After repair, go to step  10 .
5. Test Black wire between fuel sender harness connector and PCM (Blue) harness connector C1 terminal No. 23 for open circuit or high resistance or short to voltage. See Fig 1 . If problem is not found, go to step  7 . If problem is found, repair as necessary. After repair, go to step  10 .
6. Check for poor connections at fuel level sender harness connector. If poor connections are not found, go to step  8 . If poor connections are found, repair as necessary. After repair, go to step  10 .
7. Check for poor connections at PCM harness connector. If poor connections are not found, go to step  9 . If poor connections are found, repair as necessary. After repair, go to step  10 .
NOTE: Fuel level sender is an integral part of fuel pump assembly.
8. Replace fuel level sender. See FUEL PUMP under FUEL SYSTEMS in appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repair, go to step  10 .
9. Replace PCM. See POWERTRAIN CONTROL MODULE  under REMOVAL & INSTALLATION. Perform set up procedure on PCM. See POWERTRAIN CONTROL MODULE/ PROGRAMMING ON BOARD  and POWERTRAIN CONTROL MODULE/ PROGRAMMING OFF BOARD  under PROGRAMMING. After repair, go to next step.
10. Turn ignition switch to OFF position. Reconnect any disconnected components and harness connectors. Using scan tool, clear DTCs. Operate vehicle within CODE ENABLE CRITERIA  conditions. Using scan tool, retrieve DTCs. If DTC resets as current, go to step  2 . If DTC does not reset as current, system is okay.

Fig 1: Identifying Powertrain Control Module Harness Connector C1 (Blue)

Courtesy of GENERAL MOTORS CORP.