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 Descriptor

DTC P1504: TCM Communication Performance

### Circuit/System Description

The controller area network (CAN) serial data bus is used by the engine control module (ECM) and automatic transmission control module (TCM) to share information. An example of information shared is engine speed, engine coolant temperature, manifold absolute pressure (MAP), throttle position and vehicle speed.

### Conditions for Running the DTC

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

• | The ignition 1 voltage is more than 10 volts.

• | The DTC runs continuously when the above conditions are met.

### Conditions for Setting the DTC

The ECM receives no valid vehicle speed data from the TCM for more than 1 second.

### Action Taken When the DTC Sets

DTC P1504 is a Type A DTC.

### Conditions for Clearing the DTC

DTC P1504 is a Type A DTC.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### 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 for scan tool information

### Circuit/System Verification

1. Engine running, observe the DTC information with a scan tool. DTC P1504 should not set.
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.

### Circuit/System Testing

1. Ignition ON, attempt to establish communication with the TCM with a scan tool.

⇒ | If no communication with the TCM, refer to Symptoms - Data Communications for further diagnosis.

2. Ignition OFF, disconnect the harness connector at the TCM.
3. Ignition ON, test for 1.5-3.4 volts between the CAN serial data low circuit terminal A7 and the CAN serial data high circuit terminal A17.

⇒ | If not within the specified range, test the CAN communication circuits between the ECM and the TCM for an open, short to ground, or a short to voltage.

⇒ | If the circuit tests normal, replace the ECM.

4. If the circuits test normal, replace the TCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for engine and transmission control module replacement, setup, and programming