B1783

B1783-01-STOP LAMP CONTROL - GENERAL ELECTRICAL FAILURE

For a complete wiring diagram, refer to the Wiring Information.

- When Monitored:
With the ignition on and no system under or over voltage condition present.

- Set Condition:
The Anti-lock Brake System (ABS) Module has detected improper voltage level at the stop lamp relay pin.





Diagnostic Test

1. VERIFY THE DTC IS ACTIVE

NOTE: This DTC must be active for the results of this test to be valid.

1. Turn the ignition on.
2. With the scan tool, read and record the DTCs.
3. With the scan tool, read and record the Environmental Data to help identify the conditions in which the DTC was set.
4. With the scan tool, erase the DTCs.
5. Start the engine.
6. With the scan tool, read and record the DTCs.

Is the DTC active at this time?

Yes

- Go To 2

No

- Perform the ABS-INTERMITTENT CONDITION TEST. Initial Inspection and Diagnostic Overview.

2. CHECK THE STOP LAMP RELAY
1. Turn the ignition off.
2. Install a known good relay.
3. Ignition on, engine not running.
4. With the scan tool, erase the DTCs.
5. Start the engine.
6. Press and release the brake pedal several times
7. With the scan tool, read and record the DTCs.

Does the DTC remain active

Yes

- Go To 3

No

- Install a new Stop Lamp relay.
- Perform the ABS VERIFICATION TEST. ABS Verification Test.

3. CHECK THE (B221) STOP LAMP RELAY SIGNAL FOR A SHORT TO VOLTAGE
1. Measure the voltage of the (B221) Stop Lamp Relay Signal circuit in the ABS Module harness connector.

Is there any voltage present?

Yes

- Repair the (B221) Stop Lamp Relay Signal circuit for a short to voltage.
- Perform the ABS VERIFICATION TEST. ABS Verification Test.

No

- Go To 4

4. CHECK THE (B221) STOP LAMP RELAY SIGNAL FOR A SHORT TO GROUND
1. Measure the resistance between ground and the (B221) Stop Lamp Relay Signal in the ABS Module harness connector.

Is the resistance above 100 ohms?

Yes

- Go To 5

No

- Repair the (B15) Brake Signal 1 circuit for a short to ground.
- Perform the ABS VERIFICATION TEST. ABS Verification Test.

5. CHECK THE (B221) STOP LAMP RELAY SIGNAL FOR AN OPEN OR HIGH RESISTANCE
1. Turn the ignition off.
2. Disconnect the Stop Lamp Switch connector.
3. Using a 12 volt test light connected to 12 volts, check the (B221) Stop Lamp Relay Signal circuit in the ABS Module harness connector.

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Is the test light illuminated and bright?

Yes

- Replace the Anti-Lock Brake System (ABS) Module. Anti-Lock Brake System Module - Removal.
- Perform the ABS VERIFICATION TEST. ABS Verification Test.

No

- Repair the (B221) Stop Lamp Relay Signal circuit for an open circuit or high resistance.
- Perform the ABS VERIFICATION TEST. ABS Verification Test.