For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptors

DTC P0601: Control Module Read Only Memory (ROM)
DTC P0602: Control Module Not Programmed
DTC P0603: Control Module (TCM) Long Term Memory Reset
DTC P0604: Control Module Random Access Memory (RAM)

### Circuit/System Description

This diagnostic applies to internal microprocessor integrity conditions within the transmission control module (TCM) system. This diagnostic also addresses if the TCM is not programmed.

### Conditions for Running the DTC

• | The ignition is ON, or the engine is operating.

• | The DTCs run once an ignition cycle.

### Conditions for Setting the DTC

#### P0601

The TCM detects that the checksum calculation does not match the expected checksum.

#### P0602

The TCM is identified as not programmed.

#### P0603

The TCM detects an incorrect copy of non-volatile memory.

#### P0604

The TCM detects a random access memory (RAM) read/write error.

### Action Taken When the DTC Sets

#### P0601 and P0602

• | DTCs P0601, and P0602 are Type A DTCs.

• | The transmission will operate in 5th gear in D or M range, 2nd gear in L range.

#### P0603

• | DTC P0603 is a Type A DTC.

• | The TCM uses default EEPROM values.

• | The TCM disables engine start.

#### P0604

DTC P0604 is a Type A DTC.

### Conditions for Clearing the DTC

DTCs P0601, P0602, P0603, and P0604 are Type A DTCs.

### Reference Information

#### Description and Operation

Electronic Component Description

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

### Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. Verify that DTC P0602 does not fail this ignition cycle.

⇒ | If DTC P0602 failed this ignition, reprogram the TCM. Refer to Control Module References. If DTC P0602 resets, replace the TCM.

2. Observe the DTC information with a scan tool. Verify that DTCs P0601, P0603, and P0604 do not set this ignition cycle.

⇒ | If any of the DTCs P0601, P0603, or P0604 are set this ignition cycle replace the TCM, refer to Transmission Control Module Removal procedure and Transmission Control Module Installation procedure.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Refer to Control Module References for TCM replacement, setup, and programming.