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 U1500 00: Inter-Device Dedicated Bus 1

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
CAN Bus High Serial Data | U1500 | U2105-U2199 (U2142 or U2143 only) | U1500 | --
CAN Bus Low Serial Data | U1500 | U2105-U2199 (U2142 or U2143 only) | U1500 | --
CAN Bus High Terminated Serial Data | U1500 | U2105-U2199 (U2142 or U2143 only) | U1500 | --
CAN Bus Low Terminated Serial Data | U1500 | U2105-U2199 (U2142 or U2143 only) | U1500 | --

### Circuit/System Description

Modules connected to the CAN bus serial data circuits are high speed serial data modules that monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

The electronic brake control module (EBCM) activates the other modules connected to the CAN serial data circuits by applying voltage when the ignition key is in ACC, ON or START. The EBCM, Yaw Rate Sensor, and the Steering Angle Sensor are the only modules connected to the CAN bus serial data circuits. For more information on CAN bus serial data refer to Data Link Communications Description and Operation .

### Conditions for Running the DTC

• | The system voltage is between 9-16 volts.

• | The vehicle power mode master requires serial data communication to occur.

### Conditions for Setting the DTC

A no communication condition exists on the CAN bus serial data for the EBCM.

### Action Taken When the DTC Sets

• | The Vehicle Stability Enhancement System (VSES), if equipped, and Traction Control System (TCS) will not function.

• | System OFF lamps will illuminate for these systems.

### Conditions for Clearing the DTC

• | A current DTC clears when the malfunction is no longer present.

• | A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

### Diagnostic Aids

• | An open on 1 CAN Bus circuit will not cause a U1500 DTC.

• | If there are multiple non-communicating modules choose the one farthest from the EBCM.

### Reference Information

#### Schematic Reference

Antilock Brake System Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Data Link Communications Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for Scan Tool Information

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector of the yaw rate sensor.
2. Ignition ON, with a scan tool attempt to retrieve data from the steering wheel angle sensor in Chassis/Electronic Brake Control Module. Data should be available.

⇒ | If data is not available, test the serial data circuits for a short to ground or a short to voltage. If the circuits test normal, replace the steering wheel angle sensor.

3. Replace the yaw rate sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | GMLAN Wiring Repairs

• | Steering Wheel Position Sensor Replacement

• | Vehicle Yaw Sensor Replacement

• | Control Module References for module replacement, setup, and programming