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 P0603: Transmission 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.

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

#### P0601

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

#### 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 P0604

• | DTCs P0601 and P0604 are Type A DTCs.

• | The transmission will operate in 4th gear in D range, Reverse in R range.

#### P0603

• | DTC P0603 is a Type A DTC.

• | The TCM uses default EEPROM values.

### Conditions for Clearing the DTC

DTCs P0601, P0603 and P0604 are Type A DTCs.

### Reference Information

#### Schematic Reference

Automatic Transmission Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Electronic Component Description

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References

### Circuit/System Verification

1. Observe the DTC information with a scan tool. Verify that DTCs P0601, P0603, P604 do not set this ignition cycle.

⇒ | If any of the DTCs P0601, P0603, or P604 are set this ignition cycle replace the TCM.

2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for TCM replacement, setup, and programming