Confusing Fog Light

[Hilux2400]

996 C2 2003

I was checking the lights and noticed that my rear fog light was not working. I thought that this would be simple enough to fix. I removed the light housing and replaced the bulb, but still no light. I thought that both bulbs must be faulty, but when I checked with a meter both were OK. I also thought that if the bulb had gone my warning light would come on, on the dashboard, but it had not.

Next I checked the voltage at the bulb holder and found it to be 12.2/12.4. A bit low even with the engine running. I checked the voltage at the jump posts and that was OK.

I next checked the input voltage at the light unit multi-plug and found the input was higher than the output, so there was obviously resistance in the plug. When I separated the plug I found that the fog light probe had corrosion on it which was not allowing sufficient current to pass to light the bulb, but enough current was passing to show a meter reading. This is why the dash warning light did not come one. The warning system was recording a "made circuit" so no fault was showing up. However, as the circuit was not "good" the unit would not light the bulb.

I think there might be a lesson here for other fault readers. As some faults are recorded through a circuit continuity check, it doesn't mean that the circuit is fully functional. It's always worth looking at the entire track to see if all the connections are sound and there is low resistance throughout.

H

[Wausau 911]

My parking / city lights weren't functioning when I bought the car and no warning light was showing, maybe only some lights are tied to warning system, Loren can you shed some of your knowledge here?

[RFM]

Rear fog and front parking lights are not recorded in the control system in a 996/986, only the later types with control box have this option, i thought.

[Loren]

My parking / city lights weren't functioning when I bought the car and no warning light was showing, maybe only some lights are tied to warning system, Loren can you shed some of your knowledge here?

RFM is correct. No warning system for lights in 9x6 series cars - those did not come in until 2005 with the 9x7 series cars. The 9x7 series cars have several new control modules through-out the car. The electronic components were one of the major changes from 9x6 to 9x7 series cars.