GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2003 🢒 ION 🢒 DTC 🢒 DTC P0604

Circuit Description

A normal function of the transmission control module (TCM) is to perform an internal test that verifies the read and write capability of the random access memory (RAM). This diagnostic detects faults in the RAM by writing test data to the RAM, reading the same data, and then comparing the two datasets. When the TCM detects that the data that was read from the RAM is differentfrom the test data that was written to the RAM, DTC P0604 sets. DTC P0604is a type A DTC.

Conditions for Running The DTC

The engine is running.

Conditions for Setting The DTC

The data read from RAM does not match the test data written to the RAM.

Action Taken When the DTC Sets
    • The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL).
    • The TCM freezes all ratio control functions, including the ratio control motor and desired speed ratio.
    • The TCM discontinues use of the closed loop ratio control algorithm. This causes the speed ratio to be defaulted and possibly not accurate. Theresulting open loop control may or may not provide optimum ratio performance.
    • The TCM inhibits TCC engagement.
    • The TCM commands maximum line pressure.
    • The TCM no longer inhibits shifting to between reverse and drive when moving.
    • The TCM turns power off to the TCC enable solenoid valve.
    • The TCM discontinues torque management.
    • The TCM freezes garage shift transmission adaptive functions.
    • The TCM freezes main line pressure transmission adaptive functions.
    • The TCM freezes torque converter clutch (TCC) transmission adaptive functions.
    • The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records.
    • 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 P0604 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 switch 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?

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Go to Step 2

Go to Diagnostic System Check - Engine Controls in Engine Controls - 2.2L (L61)

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 Failure Records. Using the Clear Eng./Trans. DTC Info function erases the Failure Records from 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.
  4. Clear the DTC.
  5. Turn OFF the ignition for at least 30 seconds.
  6. Turn ON the ignition.

Did DTC P0604 reset?

--

Go to Step 3

Go to Diagnostic Aids

3

Replace the TCM. Refer to Transmission Control Module Replacement .

Is the action complete?

--

Go to Step 4

--

4

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Turn OFF the ignition for at least 30 seconds.
  4. Start the engine.
  5. Select Specific DTC.
  6. Enter DTC P0604.

Has the test run and passed?

--

Go to Step 5

Go to Step 2

5

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 - 2.2L (L61)

System OK