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 provide 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

• | Engine Control Module Connector End Views

• | Engine Controls 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

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### Circuit/System Verification

1. Start the engine, observe the DTC information with a scan tool. DTC P1504 should not set.
2. If the vehicle passes the Circuit/System Verification Test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

### 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 DTC U0100-U0299 for further diagnosis.

2. Ignition OFF, disconnect the harness connector of the TCM.
3. Ignition ON, verify that 1.5-3.4 volts is available between the CAN serial data low and the CAN serial data high circuits.

⇒ | If the voltage is 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 circuits/connections test OK, replace the ECM.

4. If the circuits/connections test OK, 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