Diagnostic Test

WARNING: This page is about a different car, the 2009 Jeep Patriot and 2009 Jeep Compass. However, it is still accessible from the selected car via links, so may be relevant.

CHECK FOR DTC C1091-ABS BRAKE LAMP CONTROL CIRCUIT HIGH
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, record and erase DTCs.
3. Start the engine.
4. Apply brake pedal firmly with at least 80 bar (1160 psi.).
5. With the scan tool, read the DTCs.
  Does the scan tool display: C1091-ABS BRAKE LAMP CONTROL CIRCUIT HIGH?
  
  Yes
  - Go to step 2
  No
  - Perform ABS-INTERMITTENT CONDITION TEST. See DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure .
CHECK CONNECTOR/TERMINAL FOR DAMAGE
NOTE: Check all terminals for broken, bent, pushed out or corroded terminals.
1. Turn the ignition off.
2. Inspect the Anti-Lock Brake Module harness connector and the Brake Lamp Activation Relay harness connector.
  Is the ABM or any of the connectors/terminals damaged?
  
  Yes
  - Repair as necessary.
  - Perform ABS VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure .
  No
  - Go to step 3
CHECK (B122) BRAKE LAMP ACTIVATION RELAY CONTROL SHORTED TO VOLTAGE

Fig 1: CHECKING BRAKE LAMP ACTIVATION RELAY CONTROL FOR SHORT TO VOLTAGE
Courtesy of CHRYSLER LLC
1. Turn the ignition off.
2. Disconnect the ABM.
3. Disconnect the Brake Lamp Activation Relay.
4. Start the engine.
5. Using a 12-volt test light connected to ground, probe the (B122) Brake Lamp Activation Relay Control at the Brake Lamp Activation Relay harness connector.
  Does the test light illuminate brightly?
  
  Yes
  - Repair the short to voltage in the (B122) Brake Lamp Activation Relay Control Circuit.
  - Perform ABS VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure .
  No
  - Go to step 4
BRAKE LAMP ACTIVATION RELAY

Fig 2: Checking Brake Lamp Activation Relay Control Circuit
Courtesy of CHRYSLER LLC
1. Turn the ignition off.
2. Measure the resistance across the relay between the (B122) Brake Lamp Activation Relay Control Circuit and the ((A924) Fused B+ Circuit.
  Is the resistance 75 - 95 Ohms?
  
  Yes
  - Replace the ABM in accordance with the Service Information.
  - Perform ABS VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure .
  No
  - Replace the Brake Lamp Activation Relay in accordance with the Service Information.
  - Perform ABS VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure .