Diagnostic Routine A
Diagnostic Routine A
Diagnostic Overview
The Horn Is Inoperative
Refer to Wiring Diagram Set 44 for schematic and connector information Electrical Diagrams.
Normal Operation and Fault Conditions
REFER to Horn Operation .
Visual Inspection and Diagnostic Pre-checks
Inspect the BJB (Battery Junction Box) fuses 20 (15A) and 23 (5A).
Pinpoint Test
1. CHECK THE BCM (Body Control Module) OUTPUT
1. Ignition ON.
2. Using a scan tool, view BCM (Body Control Module) PIDs (Parameter Identifications).
3. Select the active command BCM (Body Control Module) HORN PID (Parameter Identification). Command the horn ON and then OFF.
Does the horn sound when commanded on?
2. CHECK HORN OPERATION WITH HORN SWITCH CIRCUITS ISOLATED
NOTE: Test is carried out with jumper at female (harness) side of connector.
1. WARNING: Turn the ignition OFF and wait one minute to deplete the backup power supply. Failure to follow this instruction may result in serious personal injury or death in the event of an accidental deployment.
Ignition OFF and wait one minute.
2. Remove the driver air bag module. REFER to Driver Air Bag Module. Driver Air Bag Module
3. Disconnect: Clockspring C218A.
4. Connect a fused jumper wire:
Does the horn sound?
3. CHECK THE HORN CIRCUIT FOR VOLTAGE
1. Ignition ON.
2. Measure:
Is the voltage greater than 11 volts?
4. CHECK THE HORN CIRCUIT FOR A SHORT TO VOLTAGE
1. Ignition OFF.
2. Disconnect: BCM (Body Control Module) C2280C.
3. Ignition ON.
4. Measure:
Is any voltage present?
5. CHECK THE HORN CIRCUIT FOR AN OPEN
1. Ignition OFF.
2. Disconnect: BCM (Body Control Module) C2280C.
3. Measure:
Is the resistance less than 3 ohms?
6. CHECK THE HORN SWITCH GROUND CIRCUIT FOR AN OPEN
1. Measure:
Is the resistance less than 3 ohms?
7. CHECK HORN OPERATION WITH CLOCKSPRING ISOLATED
NOTE: Test is carried out with jumper at male (clockspring) side of connector.
1. Ignition OFF.
2. Connect: Clockspring C218A.
3. Disconnect: Clockspring C218B.
4. Connect a fused jumper wire:
Does the horn sound?
8. CHECK HORN OPERATION WITH STEERING WHEEL HARNESS ISOLATED
NOTE: Switch harness may be temporarily removed from air bag assembly for test purposes.
1. Ignition OFF.
2. Connect: Clockspring C218B.
3. Disconnect: Clockspring C217A.
4. Disconnect: Clockspring C217B.
5. Connect a fused jumper wire:
Does the horn sound?
9. CHECK HORN OPERATION WITH UPPER STEERING WHEEL HARNESS ISOLATED
NOTE: Test is carried out with jumper at female (harness) side of connector. Switch harness can be temporarily removed from air bag assembly for test purposes.
1. Ignition OFF.
2. Measure:
3. Measure:
Are the resistances less than 3 ohms?
10. SUBSTITUTE A KNOWN GOOD RELAY
1. Ignition OFF.
2. Substitute a known good horn relay.
3. Operate the horn switch.
Does the horn sound?
11. CHECK THE HORN OPERATION WITH RELAY CONTROL ISOLATED
1. Remove: Horn Relay.
2. Connect a fused jumper wire:
Does the horn sound?
12. CHECK THE HORN OPERATION WITH BCM (Body Control Module) ISOLATED
1. Ignition OFF.
2. Disconnect: BCM (Body Control Module) C2280A.
3. Connect a fused jumper wire:
Does the horn sound?
13. CHECK THE HORN RELAY CONTROL CIRCUIT FOR VOLTAGE
1. Measure:
Is the voltage greater than 11 volts?
14. CHECK THE HORN RELAY LOAD CIRCUIT FOR VOLTAGE
1. Measure:
Is the voltage greater than 11 volts?
15. CHECK FOR VOLTAGE AT THE HORN
1. Connect: Horn Relay.
2. Disconnect: Horn.
3. Press and hold the horn switch.
4. Measure:
Is the voltage greater than 11 volts?
16. CHECK THE HORN GROUND CIRCUIT FOR AN OPEN
1. Press and hold the horn switch.
2. Measure:
Is the voltage greater than 11 volts?
17. CHECK FOR CORRECT BCM (Body Control Module) OPERATION
1. Ignition OFF.
2. Disconnect and inspect the BCM (Body Control Module) connectors.
3. Repair:
- corrosion (install new connector or terminals- clean module pins)
- damaged or bent pins- install new terminals/pins
- pushed-out pins- install new pins as necessary
4. Reconnect the BCM (Body Control Module) connectors. Make sure they seat and latch correctly.
5. Operate the system and determine if the concern is still present.
Is the concern still present?
