Check engine light is NOT coming on. Why?

[DerekTheGreat]

Hello everyone,

I've got an '88 townie with a analog dash and a pod with 9 dummy lights to the left of it. My girlfriend has an 89 which has the exact same set up. When you flip the key to run (I always do that to prime the fuel system) the check engine light, along with many others are supposed to come on. All of mine come on EXCEPT the yellow check engine light, which is on the middle row, right side. Her car's light DOES come on like it is supposed to. I went to the junk yard and tore apart one with a digital dash to get spare light bulbs since I figured mine was burnt out. Once I took my car apart I swapped the light bulb that was in the check engine slot to the one for the door slot and it still didn't work, so the lights aren't the issue. With the engine running I even tried unplugging things underhood to force it to come on. That was dumb. The light didn't come on and now the car's idle surges a bit as it calms down when started cold. So, is my pod bad or is my car just weird? I read other posts around here where people say that only the 89's got the CEL yet my car has it too. Perhaps the computer isn't programmed to light it up? Also, my car appears to be an early 88 model, the core support is dated Sept. 1st, 1987 and I've noticed that the plugs for the speakers and such are like what my '85 LTD had. What gives?

Thanks for reading and I appreciate all input!

Derek

[sly]

Try reading codes. I just sold a car that the ECM that came with it didn't want to talk (light the diag port). It didn't have a light, but code readers never got anything from it. The car ran fine. If a code reader can't talk to the ECM, there may be an issue with the ECM. Also, I think the wire to that bulb goes to the ECM by way of the diag port itself. Check that for broken wires.

The wire you're interested in is the Self-Test Output (pin 4).

[DerekTheGreat]

That's what I was thinking, but even if it is bad it seems like it would be a PITA to get the ECM out.

I don't have any sort of scanner, and that picture shows something that looks like a pregnancy tester lol. I know where that connector is so I'm guessing I put a circuit test light in pin 4 and connect it to the battery while jumping pins 1&2 together?

[sly]

nah... 10mm (3/8) hex bolt on the ECM harness. Loosen that (might have to move the cruise servo to get at it), and pull the harness off (might wanna disconnect the negative battery cable for good measure) and then dive under the dash and it pops out of the bracket with some persuasion. It's not that hard. Maybe 15-20 minutes to swap one out.

[DerekTheGreat]

Really??

Alright, I'll hit a yard tomorrow and if there's a dead panther I'll give it a shot. Would an 89's ECM be a direct swap?

[sly]

any 86-91 panther should be a direct swap (except 91 TC) but you'll want 88-91 for the build in cruise control to make sure that will work.

[DerekTheGreat]

Cool, thanks sly!

If I find one tomorrow I'll post back with results..

[sly]

have you tried reading codes first to find out of the ECM is bad or not?

[88grandmarq]

pictures of town car cluster? I bet it doesnt have a yellow check engine light

http://www.crownvic.net/ubbthreads/u...36#Post1500636

[gadget73]

I've never seen one in an '88 either.

[ootdega]

I've never seen one in an '88 either.

Wikipedia says there wasn't a Check Engine light until '89. Which means it has already been swapped, which means there may very well be something else causing it.

I dunno anything about it, that's just deduction on my part.

[gadget73]

well, if its a lamp cluster out of an 89, then its a fair bet that the wires to power the light don't exist in the 88. The center lamp in an 88 I believe should be the "alarm" light, which is active if you had the optional alarm system.

[DerekTheGreat]

Ok Ashley and I went to several yards and after admiring all of the dead cars we got down to business and pulled an ECM/PCM out of a '91 Grand Marquis. Swapped it with mine and still no light. I promise you guys that it exists, it's the same dummy light pod that my Ashley's '89 has, infact the instrument cluster and interior are identical save for the interior color and C-pillar area; hers doesn't have the Frenched window. I'll take a pic tonight but the yellow CEL light is in the middle row, right side. I looked through it when I pulled its bulb out to swap with others, which didn't fix it either. The car belonged to a 94 year old man who bought it new and I broke the foam gasket that insulates the clear "three brick" window from the actual cluster when I took the dash apart the other day. So, any more ideas?

Thanks for your help fellas, I appreciate it!

[sly]

If no change, either the wire from the diag port under the hood is broken or like others said, you have an 89 pod and the 88 was not actually wired for that.

[DerekTheGreat]

I took some pics of that pod...



The first one shows just the pod and the second one shows the pod and what lights up when you flip the key over to the run position. This pod is identical to my gal's 89. You can see the check engine light exists in the right side middle. The opposite is the light for the alarm, which I figure I don't have since it doesn't flash like the owner's manual says it should. Owners manual also says the check engine light should come on when the key is in the run position. From what I can tell this dash had never been torn apart before, I broke the seal the other day when I checked out that pod's bulbs. Anything else I can check?

I'll check the wire for the diag port but where I can I trace it back to? Every wire under the hood looks good. Car was built Sept. 1st 1987.........

Thanks,

Derek