B004A
DTC B004A
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptor
DTC B004A 00
- Door Unlock on Crash Relay Circuit Malfunction
Diagnostic Fault Information
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 (Door Lock/Indicator Schematics)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Power Door Locks Description and Operation (Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning) 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 (Verification Tests) after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Control Module References (Programming and Relearning) for underhood fuse block replacement, setup, and programming