DTC Troubleshooting: P0643 (133)
DTC P0643:
 Sensor Reference Voltage A Circuit High Voltage
NOTE: Before you troubleshoot, record all freeze data and review the general troubleshooting information.
  1. Turn the ignition switch ON (II).
  1. Clear the DTC with the HDS.
  1. Check for Temporary DTCs or DTCs with the HDS.
Is DTC P0643 indicated?
YES -
Go to Step 4 .
NO -
Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the APP sensor and the ECM.■
  1. Turn the ignition switch OFF, and wait 2 minutes.
  1. Disconnect ECM connector No. 2 (58P).
  1. Turn the ignition switch ON (II).
  1. Measure voltage between body ground and ECM connector No. 2 terminals No. 14, No. 15 individually.
Is there battery voltage?
YES -
Repair short to power in the wire between the APP sensor and ECM connector No. 2 terminal No. 14 (No. 15) * , then go to Step 12 .
NO -
Go to Step 8 .
*: APSBVCC line
  1. Turn the ignition switch OFF.
  1. Disconnect the APP sensor 6P connector.
  1. Check for continuity between ECM connector No. 2 terminal No. 1 and APP sensor 6P connector terminal No. 3.
Is there continuity?
YES -
Repair short in the wire between the APP sensor and ECM connector No. 2 terminal No. 1, No. 3 or No. 5 then go to Step 12 .
NO -
Go to Step 11 .
  1. Check for continuity between ECM connector No. 2 terminal No. 1 and APP sensor 6P connector terminal No. 6.
Is there continuity?
YES -
Repair short in the wire between the APP sensor and ECM connector No. 2 terminal No. 1, No. 3 or No. 5 then go to Step 12 .
NO -
Go to Step 16 .
  1. Reconnect all connectors.
  1. Turn the ignition switch ON (II).
  1. Reset the ECM with the HDS.
  1. Check for Temporary DTCs or DTCs with the HDS.
Is DTC P0643 indicated?
YES -
Check for poor connections or loose terminals at the APP sensor and the ECM, then go to Step 1 .
NO -
Troubleshooting is complete. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.■
  1. Reconnect all connectors.
  1. Check for Temporary DTCs or DTCs with the HDS.
Is DTC P0643 indicated?
YES -
Check for poor connections or loose terminals at the APP sensor and the ECM. If the ECM was updated, substitute a known-good ECM, then recheck. If the ECM was substituted, go to Step 1 .
NO -
If the ECM was updated, troubleshooting is complete. If the ECM was substituted, replace the original ECM. If any other Temporary DTCs or DTCs were indicated in Step 13 , go to the indicated DTC's troubleshooting.■