Pinpoint Test H: The STOPLAMPS Are Inoperative

WARNING: This page is about a different car, the 2006 Ford F550 Super Duty, 2006 Ford F450 Super Duty, and 2006 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

H1 CHECK THE VOLTAGE TO THE STOPLAMP SWITCH
- Disconnect: Stoplamp Switch C278.
- Measure the voltage between the stoplamp switch C278-1, circuit 10 (LG/RD), harness side and ground.
  
  Fig 1: Checking Voltage To Stoplamp Switch
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : GO to H2.

No : VERIFY the CJB fuse 18 (20A) is OK. If OK, REPAIR the circuit. TEST the system for normal operation.
H2 CHECK THE STOPLAMP SWITCH
- Connect a fused jumper wire (20A) between the stoplamp switch C278-1, circuit 10 (LG/RD), harness side and the stoplamp switch C278-2, circuit 511 (LG), harness side.
  
  Fig 2: Checking Stoplamp Switch
  Courtesy of FORD MOTOR CO.
- Do the stoplamps illuminate?
Yes : INSTALL a new stoplamp switch. REFER to STOPLAMP SWITCH .

No : REPAIR circuit 511 (LG). TEST the system for normal operation.