Review
Refer to section 417-01 for a detailed description of system design and operation «Steering system» in the workshop manual.
Before diagnosing problems with the trailer lighting system, test the operation of the towing vehicle lighting system by disconnecting the connector (s) trailer lighting systems from sockets (A) vehicle power supply.
Be aware that intermittent fault messages may be due to the cycling nature of the FETs (FET).
Inspection and verification
1. Make sure the customer's complaint is valid.
2. Visually inspect for obvious electrical problems.
Mechanical factors | Electrical Factors |
3. If an obvious cause of a problem you identified or described by a customer is found, resolve it before proceeding to the next steps (if possible).
4. Use an approved diagnostic system or scan tool (tester), to retrieve all DTCs before referring to the symptom table or DTC index (DTC).
Since DTCs are stored in more than one module, a complete vehicle data readout is recommended.
Clear all DTCs after troubleshooting.
Symptom table
Symptom | Possible reasons | Actions |
Trailer brake lights not working | Check the condition of the lamp and fuse (see visual inspection table). Check trailer brake light circuit. Check the operation of the brake light switch. Refer to the electrical manual. | |
Dim brake light (ov) trailer | Check the condition and power of the lamp. Check trailer brake light circuit. Check the operation of the brake light switch. Refer to the electrical manual. | |
Stop signal (s) trailers are constantly on fire | Check trailer brake light circuits. Check the operation of the brake light switch. Refer to the electrical manual. | |
Fog lamp not working (s) trailer | Check the condition of the lamp and fuse (see visual inspection table). Check the electrical circuit of the trailer fog lights. Refer to the electrical manual. | |
Dim fog light (to her) trailer | Check the condition and power of the lamp. Check the electrical circuit of the trailer fog lights. Refer to the electrical manual. | |
Fog lamp (And) trailers are constantly on fire | Electrical circuit malfunction | Check the electrical circuit of the trailer fog lights. Refer to the electrical manual. |
Back light (And) and a lantern (And) trailer license plate lights not working | Check the condition of the lamp and fuse (see visual inspection table). Check the electrical circuit of the rear and license plate lights of the trailer. Check the operation of the rear and license plate relays on the trailer. Refer to the electrical manual. | |
Dim rear light (to her) and a lantern (to her) trailer license plate lights | Check the condition and power of the lamp. Check the electrical circuit of the rear and license plate lights of the trailer. Check the operation of the trailer marker lamp relay. Refer to the electrical manual. | |
Rear light stays on all the time (And) and a lantern (And) trailer license plate lights | Check the electrical circuit of the rear and license plate lights of the trailer. Check the operation of the rear and license plate relays on the trailer. Refer to the electrical manual. | |
Pointer not working (And) trailer turning | Check the condition of the lamp and fuse (see visual inspection table). Check trailer turn signal circuit. Refer to the electrical manual. | |
dim pointer light (to her) trailer turning | Check the condition and power of the lamp. Check turn signal circuits | |
Pointer (And) trailer turning light constantly on | Electrical circuit malfunction | Check the condition of the lamp and fuse (see visual inspection table). Check trailer turn signal circuit. Refer to the electrical manual. |
Flashlight not working (And) trailer reversing | Check the condition of the lamp and fuse (see visual inspection table). Check the electrical circuit of the trailer reversing lights. Check the operation of the trailer reversing lamp relay. Refer to the electrical manual. | |
dim lantern light (to her) trailer reversing | Check the condition and power of the lamp. Check the electrical circuit of the trailer reversing lights. Check the operation of the trailer reversing lamp relay. Refer to the electrical manual. | |
Flashlight (And) trailer reverse light constantly on | Check the electrical circuit of the trailer reversing lights. Check the operation of the trailer reversing lamp relay. Refer to the electrical manual. | |
Pilot lamp (s) does not work | Check fuse (And) (see visual inspection). Check the electrical circuit of the control lamps. Refer to the electrical manual. Check for DTCs that indicate a problem with the instrument panel or CAN system. | |
No battery power to trailer electrical system | Check the condition of the fuse (see visual inspection table). Check trailer battery circuit. Refer to the electrical manual. | |
No power when ignition on trailer electrical system | Check the condition of the fuse (see visual inspection table). Check the trailer electrical circuit with the ignition on. Check the operation of the trailer power relay with the ignition on. Refer to the electrical manual. |
DTC index
NOTE: Universal Scan Tools cannot read the listed codes or can only read 5-digit codes. Match the 5 digits from the scan tool with the first 5 digits of the listed 7 digit code to identify the problem (the last 2 digits give additional information read by the diagnostic system approved by the manufacturer).
DTCs | Description | Possible reasons | Actions |
B1D0811 | Trailer left turn signal circuit | Left trailer turn signal - short to ground | Refer to the guided diagnostic program for this code on the approved diagnostic system. |
B1D0815 | Trailer left turn signal circuit | Refer to the guided diagnostic program for this code on the approved diagnostic system. | |
B1D0911 | Trailer right turn signal circuit | Trailer right turn signal - short to ground | Refer to the guided diagnostic program for this code on the approved diagnostic system. |
B1D0915 | Trailer right turn signal circuit | Refer to the guided diagnostic program for this code on the approved diagnostic system. | |
U1A1449 | CAN initialization failure | Internal electronic fault | Check the power circuits and grounds of the device. Refer to the electrical manual. Customize the module configuration (modules), using an approved diagnostic system. If a module is suspected, refer to the warranty policy and procedures manual. |
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