Diagnostic Test

INTERMITTENT CONDITION
1. Turn the ignition on.
2. With the scan tool , clear all FCM DTCs.
3. Turn the Trailer Tow Lamps on.
4. With the scan tool read the DTCs.
  Does the Scan Tool read: B166B-LEFT TRAILER TOW LAMP CONTROL CIRCUIT LOW?
  
  Yes
  - Go to step 2
  No
  - The condition that caused the symptom is currently not present. Inspect the related wiring for a possible intermittent condition. Look for any chafed, pierced, pinched, or partially broken wires.
  - Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure .
(L655) LEFT TRAILER TOW BRAKE LAMP RELAY CONTROL CIRCUIT
1. Turn the ignition off.
2. Disconnect the 49 way FCM IPM harness connector.
3. Measure the resistance between ground and the (L655) Left Trailer Tow Brake Lamp Relay Control circuit.
  Is the resistance below 5.0 Ohms?
  
  Yes
  - Replace the Front Control Module (FCM) in accordance with the Service Information.
  - Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure .
  No
  - Repair the (L655) Left Trailer Tow Brake Lamp Relay Control circuit for a short to ground condition.
  - Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure .