GM Service Manual Online
For 1990-2009 cars only

DTC P0601 or P1790 Non Europe or N. American Emissions

Conditions for Setting the DTC

The transmission control module (TCM) detects a difference between the calculated checksum data and rear checksum data.

Action Taken When the DTC Sets

The TCM will request the illumination of the hold lamp and store the DTC when the TCM detects a failure on the first ignition cycle.

Conditions for Clearing the DTC

    • The TCM turns OFF the hold lamp when no further failures are detected on the next ignition cycles.
    • The scan tool can clear the DTC from the TCM history.
    • The TCM clears the DTC from the TCM history memory after 40 consecutive ignition cycles without fault.

Cause of Failure

    • Harness or connector between TCM and engine control module (ECM)
    • ECM
    • TCM

Step

Action

Yes

No

1

  1. Turn OFF the ignition.
  2. Install the scan tool.
  3. With the engine OFF, turn the ignition switch to the ON position.
  4. Select Store Freeze Frame/Failure Records from the Diagnostic Trouble Codes Information menu.
  5. Store Freeze Frame/Failure Records.
  6. Select Clear DTC Information from the Diagnostic Trouble Codes Information menu.
  7. Clear DTC Information.
  8. Perform 2 vehicle drive cycles.

Is the hold lamp ON?

Go to Step 2

Go to Step 3

2

  1. Select Request DTC by Status from the Diagnostic Trouble Codes Information menu.
  2. Request DTC by Status.

Is DTC P1790 displayed?

Go to Step 4

Go to Step 3

3

Repair the temporary connection failure of the connector. Refer to Wiring Harness and Connector Inspection Diagnosis .

Did you complete the repair?

System OK

--

4

Replace the transmission control module (TCM). Refer to Transmission Control Module Replacement .

Did you complete the replacement?

System OK

--

DTC P0601 or P1790 European and N. American Emissions

Conditions for Setting the DTC

The transmission control module (TCM) detects a difference between the calculated checksum data and rear checksum data.

Action Taken When the DTC Sets

The TCM will request the illumination of the malfunction indicator lamp (MIL) and store the DTC when the TCM detects a failure on the first ignition cycle.

Conditions for Clearing the DTC

    • The TCM turns OFF the MIL when no further failures are detected on the next ignition cycles.
    • The scan tool can clear the DTC from the TCM history.
    • The TCM clears the DTC from the TCM history memory after 40 consecutive ignition cycles without fault.

Cause of Failure

    • Harness or connector between TCM and engine control module (ECM)
    • ECM
    • TCM

Step

Action

Yes

No

1

  1. Turn OFF the ignition.
  2. Install the scan tool.
  3. With the engine OFF, turn the ignition switch to the ON position.
  4. Select Store Freeze Frame/Failure Records from the Diagnostic Trouble Codes Information menu.
  5. Store Freeze Frame/Failure Records.
  6. Select Clear DTC Information from the Diagnostic Trouble Codes Information menu.
  7. Clear DTC Information.
  8. Perform 2 vehicle drive cycles.

Is the malfunction indicator lamp (MIL) ON?

Go to Step 2

Go to Step 3

2

  1. Select Request DTC by Status from the Diagnostic Trouble Codes Information menu.
  2. Request DTC by Status.

Is DTC P1790 displayed?

Go to Step 4

Go to Step 3

3

Repair the temporary connection failure of the connector. Refer to Wiring Harness and Connector Inspection Diagnosis .

Did you complete the repair?

System OK

--

4

Replace the transmission control module (TCM). Refer to Transmission Control Module Replacement .

Did you complete the replacement?

System OK

--