For 1990-2009 cars

### Diagnostic Aids

The rear fog lamps will not operate unless the headlamps or the front fog lamps are ON.

The rear fog lamp indicator in the instrument cluster can shorten the diagnostic process. If the instrument cluster indicator comes ON, but the rear fog lamps do not come ON, the problem is either an open circuit between the rear fog lamp relay and the lamps, faulty lamps, or a bad ground for the rear fog lamps.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. The front fog lamps will not turn ON unless the parking lamps or headlamps are ON.

2. The rear fog lamp relay is located in the relay area under the instrument panel (I/P).

3. The rear fog lamp switch is powered through a diode which is taped to the body wiring harness near the I/P fuse block. If it is necessary to test power at the diode, remove the driver kick panel.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Inspect the headlamps and the front fog lamps. Do the headlamps and the front fog lamps operate? | -- | Go to Step 3 | Go to Step 2
2 | Repair the headlamps or the front fog lamps before completing this diagnostic table. Do the rear fog lamps work after the headlamps or the front fog lamps have been repaired? | -- | System OK | Go to Step 3
3 |

1. Remove the rear fog lamp bulbs.
2. Turn the headlamps ON.
3. Turn the rear fog lamp switch ON.
4. Measure the voltage at the RED wire to the rear fog lamp bulbs.

Is the voltage within the specified range?

11-14 V

Go to Step 4

Go to Step 7

4 | With the rear fog lamp bulbs removed, use an ohmmeter to measure the continuity between the BLK wire at the rear fog lamps and ground. Does the ohmmeter indicate the specified value? | 0 ohms | Go to Step 6 | Go to Step 5
5 | Repair the faulty BLK wire between the rear fog lamps and ground. Is the repair complete? | -- | System OK | --
6 | Replace the faulty fog lamp bulbs. Is the repair complete? | -- | System OK | --
7 | Inspect fuse EF14. Is either fuse open? | -- | Go to Step 8 | Go to Step 9
8 |

1. Inspect for a short circuit and repair if necessary.
2. Replace the fuse.

Is the repair complete?

--

System OK

--

9 | Measure the voltage at EF14. Is the voltage within the specified range? | 11-14 V | Go to Step 11 | Go to Step 10
10 | Repair the power supply circuit to the fuses. Is the repair complete? | -- | System OK | --
11 |

1. Remove the rear fog lamp relay.
2. Probe the relay socket terminal 30 with a voltmeter.

Is the voltage within the specified range?

11-14 V

Go to Step 13

Go to Step 12

12 | Repair the open circuit between fuse EF14 and terminal 30 of the rear fog lamp relay. Is the repair complete? | -- | System OK | --
13 |

1. With the rear fog lamp relay still disconnected, turn the headlamps ON.
2. Probe the rear fog lamp relay socket terminal 15.

Is the voltage within the specified range?

11-14 V

Go to Step 23

Go to Step 14

14 |

1. Remove the rear fog lamp switch for testing, but do not disconnect the electrical connector.
2. Turn the headlamps ON.
3. Measure the voltage at the BRN/WHT wire at the rear fog lamp switch.

Is the voltage within the specified range?

11-14 V

Go to Step 15

Go to Step 18

15 |

1. With the rear fog lamp switch removed for testing, turn the headlamps ON.
2. Turn the rear fog lamp switch to the ON position.
3. Measure the voltage at the YEL wire at the rear fog lamp switch.

Is the voltage within the specified range?

11-14 V

Go to Step 16

Go to Step 17

16 | Repair the open circuit between the rear fog lamp switch and the rear fog lamp relay terminal E. Is the repair complete? | -- | System OK | --
17 | Replace the rear fog lamp switch. Is the repair complete? | -- | System OK | --
18 |

1. Turn the headlamps ON.
2. Measure the voltage at the LT BLU wire at the fuse EF16.

Is the voltage within the specified range?

11-14 V

Go to Step 20

Go to Step 19

19 | Repair the open circuit between the fuse EF16 and the headlamp relay. Is the repair complete? | -- | System OK | --
20 | Inspect fuse EF16. Is EF16 open? | -- | Go to Step 21 | Go to Step 22
21 |

1. Inspect for a short circuit and repair if necessary.
2. Inspect the voltage at the LT BLU wire at the fuse EF16.

Is the repair complete?

--

System OK

--

22 |

1. Turn the headlamps ON.
2. Measure the voltage at the LT BLU wire at the fuse EF16.

Is the voltage within the specified range?

11-14 V

Go to Step 24

Go to Step 23

23 | Repair the open circuit between the fuse EF16 and the rear fog lamp switch. Is the repair complete? | -- | System OK | --
24 |

1. Temporarily substitute a known good relay in place of the rear fog lamp relay.
2. Turn the headlamps ON.
3. Turn the rear fog lamp switch to the ON position.

Do the rear fog lamps work with the substituted relay?

--

Go to Step 25

Go to Step 26

25 |

1. Return the substituted relay to its original position.
2. Replace the rear fog lamp relay.

Is the repair complete?

--

System OK

--

26 | Connect a jumper wire between terminal 30 and terminal 87 at the rear fog lamp relay socket. Do the rear fog lamps turn ON? | -- | Go to Step 27 | Go to Step 28
27 | Replace the rear fog lamp relay. Is the repair complete? | -- | System OK | --
28 | Repair the open circuit between the fuse EF14 and the rear fog lamp relay. Is the repair complete? | -- | System OK | --