For 1990-2009 cars

### Circuit Description

A normal function of the transmission control module (TCM) programming is to perform an internal check that verifies the integrity of the EEPROM memory and data allocations. When the TCM detects the calculated checksum is different from the EEPROM checksum, DTC P0602 will set. DTC P0602 is a type B DTC.

### Conditions For Running The DTC

#### Condition 1:

The ignition switch is in the RUN position.

#### Condition 2:

The ignition switch is in the OFF position.

### Conditions For Setting The DTC

#### Condition 1:

TCM EEPROM checksum is incorrect.

#### Condition 2:

TCM is unable to write to the EEPROM.

### Action Taken When the DTC Sets

• | Early production - The TCM illuminates the service transmission lamp (STL) and sends a MIL request to the ECM on the second consecutive drive trip that the diagnostic runs and fails. The ECM then illuminates the MIL.

• | Late production - The TCM flashes the Sport Mode Lamp and sends a MIL request on the second consecutive drive trip that the diagnostic runs and fails. The TCM then illuminates the MIL.

• | The ECM records the operating conditions in the Freeze Frame at the time of the MIL request from the TCM.

• | The transmission operates in the default mode (maximum line pressure, command 4th gear, inhibit TCC, freeze shift adapts).

### Conditions for Clearing the MIL/DTC

• | Early production - The TCM turns off the STL as soon as the fault is no longer present.

• | Late production - The TCM stops flashing the sport mode lamp as soon as the fault is no longer present.

• | The ECM turns off the MIL after three consecutive drive trips during which the TCM sends no MIL request.

• | A History DTC clears after forty consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission related diagnostic.

• | The scan tool clears the MIL/DTC.

• | The TCM cancels the DTC default mode actions when the fault no longer exists and the ignition switch is Off long enough in order to power down the TCM.

### Diagnostic Aids

Vehicles equipped with Fuel Cap Lamps utilize the Sport Mode lamp to indicate a transmission malfunction. In these vehicles, the Sport Mode Lamp flashes at 200 millisecond intervals when the TCM commands the lamp ON.

Vehicles not equipped with Fuel Cap Lamps are equipped with a dedicated Service Transmission Lamp (STL) on the Instrument Panel Cluster (IPC). The STL illuminates steadily when the TCM commands the lamp ON.

### Test Description

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

1. This step verifies that an operational abnormality, such as Electromagnetic Interference (EMI), did not take place during TCM power up.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to On-Board Diagnostic System Check
2 |

1. Install the Scan Tool .
2. With the engine OFF, turn the ignition switch to the RUN position.

Important: Before clearing the DTC, use the Scan Tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the ECM/TCM.

3. Record the DTC Failure Records.
4. Clear the DTC.
5. Turn the ignition switch to the OFF position for at least 30 seconds.
6. With the engine OFF, turn the ignition switch to the RUN position.

Did DTC P0602 reset?

--

Go to Step 3

Go to Diagnostic Aids

3 | Replace the TCM. Refer to Transmission Control Module Replacement . Is the replacement 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 the ignition switch to the RUN position for more than 2 seconds.

Did DTC P0602 reset?

--

Go to Step 2

System OK