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 B004A 00: Door Unlock on Crash Relay Circuit Malfunction

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Door Lock Relay B+ | B004A 00 | 4 | -- | --
Door Unlock Relay B+ | B004A 00 | 4 | -- | --
Central Door Lock Switch Lock/Unlock Signal | B3150 5A | 1 | 1 | --
Door Lock Relay Control | 2 | B004A 00 | 4 | --
Door Lock Indicator Control | 3 | 3 | 3 | --
Door Unlock Relay Control | 2 | B004A 00 | 4 | --
Lock Control | 2 | 2 | 2 | --
Unlock Control | 2 | 2 | 2 | --
Door Lock Relay Ground | -- | 4 | 4 | --
Door Unlock Relay Ground | -- | 4 | 4 | --
Multifunction I/P Switch Ground | -- | 1,3 | 1,3 | --
1. Central Door Lock Switch Inoperative 2. Door Locks Inoperative 3. Door Lock Indicator Malfunction 4. Crash Unlock Malfunction

### Circuit/System Description

The underhood fuse block controls the Door Lock and Door Unlock relays. Voltage is applied to both relays through the door unlock control circuit when the underhood fuse block detects a crash and will unlock all doors.

### Conditions for Running the DTC

The system voltage must be between 9-16 volts.

### Conditions for Setting the DTC

The underhood fuse block detects a fault in the crash unlock circuit.

### Action Taken When the DTC Sets

OnStar will be unable to command the doors to unlock in the event of a crash

### Conditions for Clearing the DTC

• | The DTC will be current for as long as the fault is present.

• | When the fault is no longer present, the DTC will become a history DTC.

• | A history DTC will clear after 50 ignition cycles.

### Reference Information

#### Schematic Reference

Door Lock/Indicator Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Power Door Locks 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 Verification

Command the doors to LOCK and UNLOCK with the scan tool, all doors should perform the LOCK and UNLOCK function.

### Circuit/System Testing

1. Ignition OFF, disconnect the Door Unlock relay, the Door Lock relay and the X2 harness connector at the underhood fuse block.
2. Test for less than 1 ohm between the control circuit terminal 23 and the relay circuit terminal listed below:

• | Door Unlock relay terminal 2

• | Door Lock relay terminal 2

⇒ | If greater than the specified range, test the control circuit for short to voltage or an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal listed below and ground:

• | Door Unlock relay terminal 5

• | Door Unlock relay terminal 1

• | Door Lock relay terminal 1

⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. Ignition OFF, connect the Door Unlock relay.
5. Ignition ON, verify that a test lamp illuminates between the control circuit terminal 23 and ground.

⇒ | If the test lamp does not illuminate, test the control circuit for a short to ground. If the circuit tests normal, test or replace the Door Unlock relay.

6. Ignition OFF, connect the Door Unlock relay and disconnect the Door Lock relay.
7. Ignition ON, verify that a test lamp illuminates between the control circuit terminal 23 and ground.

⇒ | If the test lamp does not illuminate, test the control circuit for a short to ground. If the circuit tests normal, test or replace the Door Lock relay.

8. If all circuits test normal, replace the underhood fuse block.

### Component Testing

1. Ignition OFF, disconnect the appropriate relay.
2. Test for 60-200 ohms between terminals 85 and 86.

⇒ | If not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

• | 30 and 86

• | 30 and 87

• | 30 and 85

• | 85 and 87

⇒ | If less than the specified value, replace the relay.

4. Test for less than 2 ohms between terminals 30 and 87A.

⇒ | If greater than the specified range, replace the relay.

5. Install a 3A fused jumper wire between relay terminal 85 and 12V. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.

⇒ | If greater than specified range, replace the relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Relay Replacement

• | Control Module References for underhood fuse block replacement, setup, and programming