cel not lighting, it's not the bulb

[dynamite196]

My exploder didn't pass emissions b/c the cel light doesn't light up at start up, everything else is fine except the bulb. Thought that was kinda BS but what are you gonna do. I figured it's the bulb but after digging in and tearing the cluster out the bulb is fine. I even put checked the cluster with a volt meter to make sure it wasn't the bulb. Sure enough there is no voltage going to the cel bulb contacts.
I'm suspecting a cut wire somewhere, does anyone have any experience with something like this? I couldn't find much using the search. Also, if anyone has wiring diagrams for the cluster or pcm so I know which wires to look for that'd be great. Thanks in advance.

 

[budwich]

basically, your check engine light needs to stay on when your key is in the "on" position.... some "people" either like to remove the bulb or cut wires to prevent it from "illuminating problems". In terms of the light... you should always be seeing voltage at the bulb as the "diagnostic system" basically switches in a ground to light the bulb at an appropriate time. Further to this, other systems in your cluster would not be functional if there was no voltage in (ie. tach, oil pressure). Of course, its depends on how you checked for voltage... if you were measuring across the bulb then it is likely that you have done "nothing" as this is an incorrect technique.... you always measure from test point to a known ground.

 

[dynamite196]

I tried retesting the circuit using your method budwich however to no avail. I did find a rather interesting problem though; it seems to me the truck has an incorrect cluster installed. For one the check engine light on the circuit board in the back of the cluster doesn't line up with the check engine light on the front. Two, the fuel cap light is what lines up with the check engine light from the circuit board which seems to correlate with the CEL (i.e when there are trouble codes present the fuel cap light is on but when there are no codes the fuel cap light goes off). Seems to me like the fuel cap light is functioning as the CEL light. Off to the dealer tomorrow to see whether my theory holds up.

 

[budwich]

well... the check engine light and the fuel light "alarm" are provided with the same voltage as I previously indicated..... so you should be finding voltage at the same / similar place on each bulb. It should be traceable. On my 96 drawing (of course, things may have changed for other years)... the ground for the CEL is on PK/LG ... Pin 9 (coming from the PCM).... while the ground for the fuel inertia switch comes in on GY/O ... Pin 11. Not sure what else to say other than there is a possibility of a "mismatch". Good luck... hopefully ford will have an answer. Again, your cel should be on when your key is switched to "on" but you have not started your vehicle.

 

[Cobraguy]

I've swapped 01 Sport clusters into my 99 and my 95. Both required a bit of wiring to make everything operate correctly. You might want to find the correct cluster and try that before you get a bunch of money tied up in it with a dealer. That would be straight time work at about $90 an hour.

 

[dynamite196]

I wouldn't dream of dropping my car off at a stealership, especially not for a problem like this. They'd be scratching their heads for a few days.. Turns out the wrong cluster was in the truck. The circuit board in the back was correct however, somebody swapped out all the gauges with white faced gauges. Got the proper ones in there and had no problem getting through inspection. The only question is whether or not the odometer is correct but that I'll probably never know.

 

[Cobraguy]

That white face cluster can be used correctly. It just needs some "modifying" to work right

 

[dynamite196]

I was considering rewiring it but it was easier to get a new cluster