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 C1090-ABS BRAKE LAMP CONTROL CIRCUIT LOW
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 the DTCs.
3. Start 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: C1090-ABS BRAKE LAMP CONTROL CIRCUIT LOW?
  
  Yes
  - Go to step 2
  No
  - Perform ABS INTERMITTENT CONDITION diagnostic procedure. 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 GROUND

Fig 1: CHECKING BRAKE LAMP ACTIVATION RELAY CONTROL FOR SHORT TO GROUND
Courtesy of CHRYSLER LLC
1. Turn the ignition off.
2. Disconnect the ABM.
3. Start the engine.
4. Using a 12-volt test light connected to ground, probe the (B122) Brake Lamp Activation Relay Control Circuit at the ABM harness connector.
  Does the test light illuminate?
  
  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
  - Go to step 4
CHECK (A924) FUSED B+

Fig 2: CHECKING FUSED B+ FOR VOLTAGE
Courtesy of CHRYSLER LLC
1. Turn the ignition off.
2. Disconnect the Brake Lamp Activation Relay.
3. Start the engine.
4. Using a 12-volt test light connected to ground, probe the (A924) Fused B+ Circuit at the Brake Lamp Activation Relay harness connector.
  Does the test light illuminate brightly?
  
  Yes
  - Go to step 5
  No
  - Check for open Fuse, if okay repair open or short to ground in the (A924) Fused B+ Circuit or short to ground in (B122) Brake Lamp Activation Relay Control circuit.
  - Perform ABS VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure .
BRAKE LAMP ACTIVATION RELAY

Fig 3: Checking Brake Lamp Activation Relay Control Circuit For Open
Courtesy of CHRYSLER LLC
1. Turn the ignition off.
2. Measure the resistance of the (B122) Brake Lamp Activation Relay Control Circuit between the Brake Lamp Activation relay and the ABM.
  Is the resistance below 5 Ohms?
  
  Yes
  - 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 .
  No
  - Repair open in the (B122) Brake Lamp Activation Relay Control circuit.
  - Perform ABS VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure .