Diagnostic Test

WARNING: This page is about a different car, the 2012 RAM Cab & Chassis. 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. Ignition on, engine not running.
2. With the scan tool, record and erase DTC's.
3. Start the engine.
4. Apply brake pedal firmly with at least 80 bar (1160 psi.).
5. With the scan tool, read DTC's.
  Does the scan tool display: C1090-ABS BRAKE LAMP CONTROL CIRCUIT LOW?
  
  Yes
  - Go To 2.
  No
  - Perform the ABS INTERMITTENT CONDITION diagnostic procedure. Refer to ABS INTERMITTENT CONDITION .
CHECK CONNECTOR/TERMINAL FOR DAMAGE
NOTE:
Check all terminals for broken, bent, pushed out, or corroded terminals.
1. Turn ignition off to the lock position.
2. Inspect the Antilock Brake System (ABS) Module harness connector and the Brake Lamp Activation Relay harness connector.
  Is the Antilock Brake Module or any of the connectors/terminals damaged?
  
  Yes
  - Repair as necessary.
  - Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .
  No
  - Go To 3.
CHECK (B401) BRAKE LAMP ACTIVATION RELAY SHORTED TO GROUND

Fig 1: Checking Brake Lamp Activation Relay For A Short To Ground
Courtesy of CHRYSLER GROUP, LLC
1. Turn the ignition off to the lock position.
2. Disconnect the ABS Module.
3. Ignition on, engine not running.
4. Using a 12-volt test light connected to ground, probe the (B401) Brake Lamp Activation Relay Circuit at the ABS Module harness connector.
  Does the test light illuminate brightly?
  
  Yes
  - Replace the Antilock Brake System (ABS) Module in accordance with the service information.
  - Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .
  No
  - Go To 4.
CHECK (A108) FUSED B(+)

Fig 2: Measuring Voltage Fused B(+)T Circuit At The Brake Lamp Activation Relay Harness Connector
Courtesy of CHRYSLER GROUP, LLC
1. Turn the ignition off to the lock position.
2. Disconnect the Brake Lamp Activation Relay.
3. Ignition on engine not running.
4. Using a 12-volt test light connected to ground, probe the (A108) Fused B(+)t Circuit at the Brake Lamp Activation Relay harness connector.
  Does the test light illuminate brightly?
  
  Yes
  - Go To 5.
  No
  - Check for open Fuse, if ok repair open or short to ground in the (A108) Fused B(+)t Circuit or short to ground in (B401) Brake Lamp Inhibit Relay circuit.
  - Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .
BRAKE LAMP ACTIVATION RELAY

Fig 3: Checking Brake Lamp Activation Relay Circuit
Courtesy of CHRYSLER GROUP, LLC
1. Turn ignition off to the lock position.
2. Measure the resistance of the (B401) Brake Lamp Activation Relay Circuit between the Brake Lamp Activation relay and the ABS Module harness connector.
  Is the resistance 5 Ohms ?
  
  Yes
  - Replace the Brake Lamp Activation Relay in accordance with the Service Information.
  - Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .
  No
  - Repair open in the (B401) Brake Lamp Inhibit Relay circuit.
  - Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .