DTC Troubleshooting: P0643 (133-4)

DTC P0643:  Sensor Reference Voltage A Circuit High Voltage

1.Turn the ignition switch ON (II).

2.Clear the DTC with the HDS.

3.Check for Temporary DTCs or DTCs with the HDS.

Is DTC P0643 indicated?


YES - Go to 4.


NO - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the FRP sensor, the MAF sensor/IAT sensor 1, the MAP sensor/IAT sensor 2, the APP sensor and the ECM.n


4.Turn the ignition switch OFF, and wait 30 seconds.

5.Disconnect ECM connectors No. 1 (96P) and No. 2 (58P).

6.Turn the ignition switch ON (II).

7.Measure voltage between body ground and ECM connector No. 1 terminals No. 8, No. 9, No. 33 and ECM connector No. 2 terminal No. 14 individually.

 

Is there battery voltage?


YES - Repair short to power in the wire between the ECM connector terminals and these sensors, then go to 18.

  • FRP sensor and ECM connector No. 1 terminal No. 9
  • MAF sensor/IAT sensor 1 and ECM connector No. 1 terminal No. 8
  • MAP sensor/IAT sensor 2 and ECM connector No. 1 terminal No. 33
  • APP sensor and ECM connector No. 2 terminal No. 14

NO - Go to 8.


8.Turn the ignition switch OFF.

9.Disconnect the connectors from these sensors:
  • FRP sensor
  • MAF sensor/IAT sensor 1
  • MAP sensor/IAT sensor 2
  • APP sensor

10.Connect FRP sensor 3P connector terminal No. 1 to body ground with a jumper wire.

 

11.Check for continuity between ECM connector No. 2 terminal No. 1 and body ground.

 

Is there continuity?


YES - Repair short in the wire between the FRP sensor and ECM connector No. 2 terminals No. 1, No. 3 or No. 5, then go to 18.


NO - Go to 12.


12.Connect MAF sensor/IAT sensor 1 5P connector terminal No. 2 to body ground with a jumper wire.

 

13.Check for continuity between ECM connector No. 2 terminal No. 1 and body ground.

 

Is there continuity?


YES - Repair short in the wire between the MAF sensor/IAT sensor 1 and ECM connector No. 2 terminals No. 1, No. 3 or No. 5, then go to 18.


NO - Go to 14.


14.Connect MAP sensor/IAT sensor 2 4P connector terminal No. 2 to body ground with a jumper wire.

 

15.Check for continuity between ECM connector No. 2 terminal No. 1 and body ground.

 

Is there continuity?


YES - Repair short in the wire between the MAP sensor/IAT sensor 2 and ECM connector No. 2 terminals No. 1, No. 3 or No. 5, then go to 18.


NO - Go to 16.


16.Connect APP sensor 6P connector terminal No. 5 to body ground with a jumper wire.

 

17.Check for continuity between ECM connector No. 2 terminal No. 1 and body ground.

 

Is there continuity?


YES - Repair short in the wire between the APP sensor and ECM connector No. 2 terminals No. 1, No. 3 or No. 5, then go to 18.


NO - Go to 22.


18.Reconnect all connectors.

19.Turn the ignition switch ON (II).

20.Reset the ECM with the HDS.

21.Check for Temporary DTCs or DTCs with the HDS.

Are any Temporary DTCs or DTCs indicated?


YES - If DTC P0643 is indicated, check for poor connections or loose terminals at the FRP sensor, the MAF sensor/IAT sensor 1, the MAP sensor/IAT sensor 2, the APP sensor and the ECM, then go to 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.


NO - Troubleshooting is complete.n

22.Update the ECM if it does not have the latest software, or substitute a known-good ECM.

23.Check for Temporary DTCs or DTCs with the HDS.

Are any Temporary DTCs or DTCs indicated?


YES - If DTC P0643 is indicated, check for poor connections or loose terminals at the FRP sensor, the MAF sensor/IAT sensor 1, the MAP sensor/IAT sensor 2, the APP sensor and the ECM, then go to 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.


NO - If the ECM was updated, troubleshooting is complete. If the ECM was substituted, replace the original ECM.n