GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2002 🢒 VUE - AWD 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - AF33-5 (M45) 🢒 DTC P1779

Circuit Description

Engine torque information is sent to the transmission control module (TCM) by the engine control module (ECM) through a communication network called the controller area network (CAN). Two circuits are used to communicate CAN data between the ECM and TCM. A fault in the CAN will not cause DTC P1779 to set by itself. If a CAN fault occurs, other DTCs will set before DTC P1779.

When the ECM sends the TCM a driver requested torque signal that is invalid, DTC P1779 will set. DTC P1779 is a type A DTC.

Conditions for Running the DTC
    • No CAN DTC U2105.
    • The ignition voltage is 8-18 volts.
    • The ignition has been ON for at least 3.0 seconds.
    • Trans. Protection Mode is OFF.
    • The engine is running.

Conditions for Setting the DTC

Engine torque signal is below the lower limit, above the upper limit, or is an unreliable value for 4 seconds.

Action Taken When the DTC Sets
    • The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL).
    • The TCM uses 300 N·m (221 lb ft) as a default value for driver requested torque.
    • The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as a Freeze Frame.
    • The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.
    • The TCM stores DTC P1779 in TCM history.

Conditions for Clearing the MIL/DTC
    • The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.
    • A scan tool can clear the MIL/DTC.
    • The TCM clears the DTC from TCM history if the vehicle completes 40  warm-up cycles without an emission-related diagnostic fault occurring.
    • The TCM cancels the DTC default actions when the ignition is OFF long enough in order to power down the TCM.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls in Engine Controls - 3.0L (L81)

2
  1. Install a scan tool.
  2. Turn ON the ignition with the engine OFF.

    3. Important: 

       • Before clearing the DTC, use the scan tool in order to record the ECM Freeze Frame and the TCM Failure Records. Using the Clear Eng./Trans. DTC Info function erases the Freeze Frame and Failure Records from the ECM and the TCM.
       • Using the Clear Eng./Trans. DTC Info function erases stored DTCs in both the ECM and TCM.

  3. Record the DTC Failure Records.

Did you record any ECM Failure Records?

--

Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 3.0L (L81)

Go to Step 3

3
  1. Clear the DTC.
  2. Turn the ignition OFF for at least 30 seconds.
  3. Start, and allow the engine to idle.

Did DTC P1779 reset?

--

Go to Step 4

Go to Intermittent Conditions in Engine Controls - 3.0L (L81)

4

Did any other DTCs set?

--

Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 3.0L (L81)

Go to Step 5

5

Replace the ECM. Refer to Engine Control Module Replacement in Engine Controls 3.0L (L81).

Is the action complete?

--

Go to Step 6

--

6

Perform the following operation to verify the repair:

  1. Select DTC on the scan tool.
  2. Select Clear Info.
  3. Start, and idle the engine.
  4. Select Specific DTC.
  5. Enter DTC P1779.

Does the DTC reset?

--

Go to Step 2

Go to Step 7

7

With the scan tool, observe the stored information, capture info and DTC info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 3.0L (L81)

System OK