GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2003 🢒 ION 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - AF23-5 🢒 DTC P0602

Circuit Description

A normal function of the transmission control module (TCM) is to perform an internal test that verifies the security of the diagnostic and shift calibration programming. The programming must contain security codes that enable a software lock to engage. The software lock is designed to prevent unauthorized changes to the diagnostics or shift calibrations. The software lock utility is processed independently from the diagnostic and shift calibration software and contains application specific data. This software lock data is entered into the TCM during the final assembly of the vehicle.

When the security codes from the diagnostic and shift calibration software fail to engage the software lock, the TCM sets DTC P0602. DTC P0602 is a type C DTC.

Conditions for Running The DTC

The ignition is ON.

Conditions for Setting The DTC

The TCM detects an unlocked calibration memory range.

Action Taken When the DTC Sets
    • The TCM requests the DIC to display the SERVICE VEHICLE message.
    • The TCM turns the Trans. Protection Mode ON. When the Trans. Protection Mode is ON, the following conditions occur:
      • The transmission will operate in 5th gear when the transmission is shifted into D or I range and 2nd gear when shifted into L range.
      • The line pressure is at maximum.
      • The torque converter clutch (TCC) is disabled.
      • The TCM freezes the transmission adaptive functions.
    • The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record.
    • 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 stores DTC P0602 in TCM history.

Conditions for Clearing the DIC/DTC
    • The TCM clears the SERVICE VEHICLE driver information center (DIC) message request, when the condition no longer exists.
    • A scan tool can clear the DIC/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 default actions when the ignition is OFF long enough in order to power down the TCM.

Diagnostic Aids

DTC P0602 may set as a result of TCM reprogramming.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step eliminates the TCM software as a possible cause of the DTC. If the DTC continues to set after reprogramming, the fault is in the TCM hardware.

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 - 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 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.
  4. Clear the DTC.
  5. Turn OFF the ignition for at least 30 seconds.
  6. Turn ON the ignition.

Did DTC P0602 reset?

--

Go to Step 3

Go to Diagnostic Aids

3

Perform the Transmission Control Module Reprogramming Procedure. Refer to Transmission Control Module Reprogramming .

Did DTC P0602 reset?

--

Go to Step 4

Go to Step 5

4

Replace the TCM. Refer to Transmission Control Module Replacement .

Is the action complete?

--

Go to Step 5

--

5

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. Turn ON the ignition.
  5. Select Specific DTC.
  6. Enter DTC P0602.

Has the test run and passed?

--

Go to Step 6

Go to Step 2

6

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