The Stoplamp Switch is a normally open switch, when the brake pedal is depressed, the EBTCM senses battery voltage. This allows the EBTCM to determine the state of the brake lamps.
| • | EBTCM detects battery voltage at all times. | 
| • | EBTCM never detects battery voltage from CKT 17. | 
| • | Both brake lamps are faulty. | 
| • | DTC C0161 is set. | 
| • | ABS and TCS remains active. | 
| • | The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used. | 
| • | 100 ignition cycles pass with no DTC(s) detected. | 
| • | It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction. | 
| • | Thoroughly inspect any circuitry that may be causing the complaint for the following conditions: | 
| - | Backed out terminals | 
| - | Improper mating | 
| - | Broken locks | 
| - | Improperly formed or damaged terminals | 
| - | Poor terminal-to-wiring connections | 
| - | Physical damage to the wiring harness | 
| • | The following conditions may cause an intermittent malfunction: | 
| - | A poor connection | 
| - | Rubbed-through wire insulation | 
| - | A broken wire inside the insulation | 
| • | If an intermittent malfunction exists refer to General Electrical Diagnosis in Wiring Systems for further diagnosis. | 
The numbers below refer to the step numbers on the diagnostic table.
Step  | Action  | Value(s)  | Yes  | No  | 
|---|---|---|---|---|
1  | Was the Diagnostic System Check performed?  | --  | ||
2  | Observe the rear brake lamps. Are the brake lamps off?  | --  | ||
3  | Disconnect the Stoplamp Switch connector C1. Are the brake lamps on?  | --  | ||
4  | Press the brake pedal. Do the brake lights come on?  | --  | ||
 Is the voltage within specifications?  | Battery voltage  | |||
6  | Replace the EBTCM. Refer to Electronic Brake and Traction Control Module Replacement . Is the replacement complete?  | --  | --  | |
7  | Repair the open or high resistance in CKT 17. Refer to Wiring Repairs in Wiring Systems. Is the circuit repair complete?  | --  | --  | |
8  | Check the STOPLAMP fuse in the I/P Fuse Block. Is the fuse OK?  | --  | ||
9  | 
 Is the voltage within specifications?  | Battery voltage  | ||
10  | Repair the open in CKT 140. Refer to Wiring Repairs in Wiring Systems. Is the circuit repair complete?  | --  | --  | |
Connect a fused jumper wire between the Stoplamp Switch harness connector terminals A and B. Do the brake lamps come on?  | --  | |||
12  | Adjust or replace the Stoplamp Switch as necessary. Is the repair complete?  | --  | --  | |
13  | 
 Is the fuse OK?  | --  | ||
14  | Repair the short to ground in CKT 140. Refer to Wiring Repairs in Wiring Systems. Is the circuit repair complete?  | --  | --  | |
15  | 
 Is the fuse OK?  | --  | ||
16  | 
 Is the fuse OK?  | --  | ||
17  | Repair the short to ground in CKT 17. Refer to Wiring Repairs in Wiring Systems. Is the circuit repair complete?  | --  | --  | |
18  | Repair CKT 17 for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Is the repair complete?  | --  | --  |