DTC Troubleshooting

Control System DTCs

DTC Troubleshooting: P0641

DTC P0641 : Sensor Reference Voltage A Malfunction

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information How To Troubleshoot The Fuel And Emissions Systems.

1. Problem verification:

Problem verification
-1. Turn the ignition switch to ON (II).

-2. Clear the DTC with the HDS.

-3. Check for Pending or Confirmed DTCs with the HDS.

Is DTC P0641 indicated?
-YES- The failure is duplicated. Go to step 2.
-NO- Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the ECM and these parts:
* MAP sensor
* Output shaft (countershaft) speed sensor
* Throttle body
* APP sensor

2. Determine possible failure area (VCC lines, others):

Determine possible failure area (VCC lines, others)
-1. Turn the ignition switch to LOCK (0).

-2. Disconnect the connectors from these parts:
* MAP sensor
* Output shaft (countershaft) speed sensor
* Throttle body
* APP sensor

-3. Turn the ignition switch to ON (II).

-4. Clear the DTC with the HDS.

-5. Check for Pending or Confirmed DTCs with the HDS.

Is DTC P0641 indicated?
-YES- Go to step 4.
-NO- Go to step 3.

3. Shorted part check:

Shorted part check
-1. Check for Pending or Confirmed DTCs with the HDS while reconnecting these parts, one at a time:
* MAP sensor
* Output shaft (countershaft) speed sensor
* Throttle body
* APP sensor

Is DTC P0641 indicated?
-YES- Replace the part that caused the DTC when it was reconnected, then do the repair verification.
-NO- Check for poor connections or loose terminals at the ECM and the following parts, then go to step 1.
* MAP sensor
* Output shaft (countershaft) speed sensor
* Throttle body
* APP sensor

4. Shorted wire check (VCC lines):

Shorted wire check (VCC lines)
-1. Turn the ignition switch to LOCK (0).

-2. Jump the SCS line with the HDS.

-3. Disconnect the following connectors.





-4. Check for continuity between these test points and body ground individually.


















Is there continuity?
-YES- Repair a short in the VCC wire between the ECM (A36, C22, or C23) and each part that was disconnected in step 2-2, then do the repair verification.
-NO- The VCC wires are OK. Update the ECM ECM/PCM Update if it does not have the latest software, or substitute a known-good ECM Service and Repair, then do the repair verification.

Repair verification:

-1. Turn the ignition switch to LOCK (0).

-2. Reconnect all connectors.

-3. Turn the ignition switch to ON (II).

-4. Reset the ECM with the HDS How To Troubleshoot The Fuel And Emissions Systems.

-5. Do the ECM idle learn procedure ECM/PCM Idle Learn Procedure.

-6. Check for Pending or Confirmed DTCs with the HDS.

Is DTC P0641 indicated?
-YES- Check for poor connections or loose terminals at the ECM and the following parts, then go to step 1.
* MAP sensor
* Output shaft (countershaft) speed sensor
* Throttle body
* APP sensor
-NO- Troubleshooting is complete. If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting.