Pinpoint Test S: The Fog Lamps 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.

S1 CHECK THE PARKING LAMPS
- Verify the parking lamp operation.
- Do the parking lamps operate correctly?
Yes : GO to S2.

No : REFER to PARKING, REAR AND LICENSE PLATE LAMPS in this section to continue diagnosis of the parking lamps.
S2 CHECK THE HIGH BEAM INDICATOR OPERATION
- Check the operation of the high beam indicator.
- Does the high beam indicator operate correctly?
Yes : GO to S3.

No : REFER to INSTRUMENT CLUSTER to continue diagnosis of the high beam indicator.
S3 CHECK HEADLAMP SWITCH OUTPUT
- Disconnect: CJB C270a.
- Key in ON position.
- Place the headlamp switch in the parking lamps ON position and engage the fog lamp switch.
- Measure the voltage between the CJB C270a-17, circuit 275 (YE) harness side and ground.
  
  Fig 1: Checking Headlamp Switch Output
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : TURN the headlamp switch off. GO to S6.

No : TURN the headlamp switch off. GO to S4.
S4 CHECK CIRCUIT 275 (YE) FOR AN OPEN
- Key in OFF position.
- Disconnect: Headlamp Switch C205a.
- Measure the resistance between the CJB C270a-17, circuit 275 (YE), harness side and the headlamp switch C205a-5, circuit 275 (YE), harness side.
  
  Fig 2: Checking Circuit 275 (YE) For Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes : GO to S5.

No : REPAIR the circuit. TEST the system for normal operation.
S5 CHECK CIRCUIT 14 (BN) FOR AN OPEN
- Measure the resistance between the headlamp switch C205a-12, circuit 14 (BN), harness side and the headlamp switch C205a-2, circuit 14 (BN), harness side.
  
  Fig 3: Checking Circuit 14 (BN) For Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes : INSTALL a new headlamp switch. REFER to HEADLAMP SWITCH . TEST the system for normal operation.

No : REPAIR the circuit. TEST the system for normal operation.
S6 CHECK THE CJB
- Connect: CJB C270a.
- Disconnect: CJB C270h.
- Place the headlamp switch in the parking lamps ON position and engage the fog lamp switch.
- Measure the voltage between the CJB C270h pin 2, circuit 478 (TN/OG), component side and ground.
  
  Fig 4: Checking CJB
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : TURN the headlamp switch off. GO to S8.

No : TURN the headlamp switch off. VERIFY the CJB fuse 43 (10A) is OK. If OK, GO to S7.
S7 CHECK CIRCUIT 12 (LG/BK) FOR AN OPEN CIRCUIT
- Connect: CJB C270h.
- Disconnect: CJB C270a.
- Measure the resistance between the CJB C270a-12, circuit 12 (LG/BK), harness side and ground.
  
  Fig 5: Checking Circuit 12 (LG/BK) For Open Circuit
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes : INSTALL a new CJB. TEST the system for normal operation.

No : REPAIR the circuit. TEST the system for normal operation.
S8 CHECK FOG LAMP GROUND
- Disconnect: Inoperative Fog Lamp.
- Measure the resistance between the LH fog lamp C152-1, circuit 57 (BK), harness side and ground; or between the RH fog lamp C162-1, circuit 57 (BK), harness side and ground.
  
  Fig 6: Checking Fog Lamp Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes : REPAIR circuit 478 (TN/OG). TEST the system for normal operation.

No : REPAIR circuit 57 (BK). TEST the system for normal operation.