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Check engine light won't light up at all but bulb is good

myf16

Well-Known Member
Joined
July 22, 2012
Messages
165
Reaction score
19
City, State
northern California
Year, Model & Trim Level
96 Explorer XLT 4WD
This is weird. 1996 4WD XLT.

I admit I was a bad boy and let the check engine light stay on for 5k miles or so. The bub burned out. No problem, I thought. I just swapped the working battery warning light bulb into that socket. But the darned thing STILL will not light up when I turn on the ignition.

What could the problem be? I tried to measure the voltage on the PC board. I don't have 3 hands but I couldn't see voltage there when turning the key. This one has me stumped.

I need this light working to pass smog. Even though the vehicle has no error codes the inspection rules say the light needs to be working to alert to future problems.

Also: what's the most cost-effective way to replace those tiny bulbs? Can I re-use the plastic socket?
 






This is weird. 1996 4WD XLT.
I admit I was a bad boy and let the check engine light stay on for 5k miles or so. The bub burned out. No problem, I thought. I just swapped the working battery warning light bulb into that socket. But the darned thing STILL will not light up when I turn on the ignition.
What could the problem be? I tried to measure the voltage on the PC board. I don't have 3 hands but I couldn't see voltage there when turning the key. This one has me stumped.
The way this indicator works is by the PCM driving "low" - which means that battery voltage is there all the time, and the PCM connects the other terminal of the bulb (pink/light green in my '98 schematic) to ground to turn it on. Are all your other indicator lights and gauges working properly? If not, check the appropriate fuse (#11 in my book). If the voltage is there, you need to probe the negative side of the bulb (that pink/light green wire) with a good bulb installed. If you see battery voltage there as well, it means the PCM is not driving the light -- I would suspect a bad connection somewhere.
 






check the appropriate fuse (#11 in my book).

You are a friggin' genius, 1998Exp. Fuse 11 was blown. I would never have thought to check fuses.
 






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