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SES lite on, but no code stored - 94 Olds Ciera

My 1994 Olds Ciera 3.1 lately has been setting the SES lite, but when I check with my code reader, it shows No Codes Stored, either history or current. I can reset the lite with the reader, and it may be weeks before it lites again.

In the past when I could get codes, this would usually be an intermittent EGR fault, that cleaning of the EGR would clear for a good long time.

The factory service manual I have says to test this No Code symptom by creating a fault by disconnecting the TPS and watching for that code to be set. If no code stored, then the PCM is faulty. That is what exactly what happens, Lite on, no code stored. So I get a PCM from a 94 Ciera at the local Pull&Pay, swap it in, and guess what, same problem !!

Just as a test of my reader, I did the same TPS test on my 94 GMC Jimmy, and I was able to get the code for "Low TPS" stored.

So either it was my bad luck to get a PCM with exact same failure, or the cause of No Code Stored lies elsewhere.

Cleaning the EGR is easy enough, but I am concerned that a new problem might crop up and I won't know what to look at.

Anyone have suggestions on where to look from here ??

--reed

Reply to
Reed
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Double check the ground on the pcm.

Reply to
Paul

OK, checked the 4 ground wires from the PCM to the transaxle ground stud. All check good , no resistance. Also checked the 12V feeds. OK also. I'm stumped :-(

--reed

Reply to
Reed

On Wed, 02 Jun 2010 22:28:27 -0600, Reed wrote:

I looked around because I have a 3.1 with 155K miles. Just cleaned the EGR for the first time this weekend because the light stayed on and stored the "insufficient flow" code. I've had an intermittent SES a few times while on the road over the last 5 years, usually at high speed up a grade or when flooring it, but never caught a stored code for those. Don't know if one was stored or it just wasn't there by the time I got a reader on it. So I don't know if it was the EGR causing that. BTW, if you don't know, chucking about 8 inches of braided cable into a drill will clear the EGR passage without pulling the throttle body. I cut an old dog cable I had in the garage and stripped the plastic coating. It was 1/4" thick, maybe 3/16". My son held the drill in slow reverse while I fed it in and used my hand to keep it from kinking. Soaked the passage with Sea Foam first, but it was completely clogged, as the Sea Foam just pooled. I had to apply some pressure to get the cable around the bend, but didn't burn my hand up. Drilled in reverse so the cable wouldn't come undone. Don't know if they're all wound the same. Saw the trick on the net with one guy using thinner speedo cable and another using heavy duty weed wacker string. Didn't have speedo cable, and though I had some pretty thick wacker string, it couldn't get through the solid carbon. Then I caught sight of the old dog cable under a pile of junk waiting to be tossed out. The kid didn't want to remove the TB cooling system plumbing, though that's probably the best way, since you can clean that up good too. Used a new EGR gasket, which they had at the auto store when I got the Sea Foam. They didn't have the TB gasket, and that cooling pipe running to the passenger side probably should get a new gasket too if you pull the TB.

Only thing I found on SES with no code stored that might fit is this

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"i had a ses light on and off for 6 months and everytime i had the car checked no code could be found then i changed the o2 sensor and the light never came on since lol,dont know why the code couldn't be found though,i had 3 different machanics check "

Since the guy calls himself blackberetta16 it might have been a 3.1.

It's something, anyway, I'd probably clean the EGR first before replacing O2 sensors though

--Vic

Reply to
Vic Smith

Reed wrote in news:AYKdnbxwjN5GzJnRnZ2dnUVZ snipped-for-privacy@earthlink.com:

I would throw a O2 sensor at it. used to see this all the time short duration fuel trim off wouldn`t set a code on a non odb2 system. KB

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Reply to
Kevin Bottorff

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