1992 Buick Lesabre Car dies at random - Need help with code

CHRIS C

MEMBER
1992 BUICK LESABRE

Engine Performance problem
1992 Buick Lesabre Automatic 122500 miles

Hello! I'm having a problem that is so random, my mechanic can't catch it in action. I have a new code that showed up today right after it died, so I'm hoping someone can help narrow down what to replace or check.

Car is a 3.8L VIN-L (1992 Buick LeSabre)

I replaced the crank sensor last June, and shortly after, the check engine light came on. Mechanic said the code was for the Cam sensor, and that the car would run with it not functioning properly, but just at a lower efficiency. So far, so good...

In December the car died while driving down my street. No sputter, just cut out as if the key had been turned off. I coasted into the driveway, and at first the car just turned over, but wouldn't start. 10 minutes later, it started right up.

Two months later it did the same thing twice in one week. Took the car into the mechanic. Car was showing the following codes:

(Based on this site: http://www.troublecodes.net/GM/92-95_38L.shtml )

41 (Cam Sensor)
17 (PCM did not detect spark...)
31 (PRNDL issue...)

Mechanic checked fuel and some other stuff - all looked good. He kept it for 4 days, driving around, parking, restarting...driving cold...driving warm - could not reproduce the problem.

Car was returned a couple weeks ago with codes cleared except for the 41 Cam Sensor code.

Today it died 5 minutes after starting. It started back up immediately. I went straight to the mechanic and the codes that showed up were:

41 (Cam sensor)
31 (PRNDL issue)
51 (MEM-Cal error)

(Note: on his scanner, 51 came up as an anti-theft code???)

I thought the PRNDL code was there previously because I mistakenly tried to start the car while it was still in gear the first time it died. But that code came up again.

I also thought the problem was happening on occasions where I'd driven for a while, stopped to run into a store, then re-started on my way home. But today I'd just left home after it being parked all night.

My mechanic thinks this is between another bad crank sensor, the ignition module, or maybe the computer?

Does the new occurrence of code 51 make the case for any one issue over the others? I don't want to change a part and then be driving around for 2 months trying to see if it will randomly die again - thus not even knowing if the repair solved the problem.

Any thoughts or suggestions would be greatly appreciated. Thanks in advance!
Chris

11 Replies

JAMES W.

MECHANIC
2,394 POSTS

If the cam sensor code keeps coming back, I'd say it's either the new sensor, or the wiring between it and the ECM. I've seen sensors bad, brand new, right out of the box. But, I'd really take a look at the sensor circuit. Hopr this helps.

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Friday, March 13th, 2009 AT 11:28 PM

CHRIS C

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Hi James - thanks for the feedback, but I don't have a new cam sensor - I have a new crank sensor.

Are you saying a bad cam sensor would cause the car to completely shut off?

My mechanic said you could pretty much run the car without the cam sensor, and that it basically just fine-tunes how the car runs.

We were both going on the belief that the cam sensor code/issue was a completely separate issue that i'd planned to address when I got some 'extra' cash. I really only included that info for 'full disclosure'. Are we on the wrong track?

I've read that the crank sensor can be bad out of the box, or fail if it's not a reliable manufacturer. But that's another $150 to fix, and I wouldn't be able to tell if it even helped since this happens only every so often.

I'm fine with replacing the crank sensor if that's what it is - but I'm wondering how these other (non-cam) codes are related to the problems I'm having and if any of those point more in one direction than another.

Is there a way to narrow it down? What would cause a MEM-CAL error? What would make that PRNDL code show up? And which of those things (if any) could make my car have a phantom stall?

I'd like a little more certainty (if possible) before I go changing parts out that *might* be the culprit.

Thanks again,
Chris

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Saturday, March 14th, 2009 AT 8:52 AM

JAMES W.

MECHANIC
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Chris, Your mechanic is correct. If the "cam" sensor fails, without this input, the ECM goes into "limp mode" and won't fine tune your fuel mixture and timing for optimum performance. You will notice a loss in performance and fuel economy.
The ECM uses the signal from the "crank sensor" to control the ignition and injector pulse timing. If the CPS fails, the engine will die instantly. CPS failures can be intermitent due to temperature and vibration.
The MEM-CAL error is when the ECM doesn't have all the information it needs to do the proper engine running calculations. This code can also put the ECM into limp mode.
PRNDL code is usually set when you try to start the engine in anything but park or neutral. Why GM did this, I don't know. They must have had a spare input they didn't know what to do with.
Hope this helps clarify.
On your phantom stall, I'd look at the CPS.

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Saturday, March 14th, 2009 AT 2:19 PM

CHRIS C

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Hi again, James :)

Thanks for the info - it sounds like we're on the same page. If you have a sec, could you please clarify a couple things for me?

I believe 3 possible parts could cause my symptoms. I'm trying to understand which codes are more likely related (or unrelated) to those 3 parts?

The Crank position sensor is at the top of the list for sure. Do the codes support this?
I hate it when people answer a question with a question, BUT, I'm going to. If I remember right, you said a new CPS was $165? That should be a $50 part at the most. And they're not that hard to change. Anyway, to answer your question, by the codes you have, my first suspect is the CPS.

Also on the list is the ignition module. If this failed intermitently, would it try to restart my car while it was in Drive? (I know I accidentally tried to restart in Drive the first time it died. But the PRNDL code was cleared, and when I started the car, it was definitely in Park. What failed part could make that show up?
I have to do it again. You said, " would it try to restart my car while it was in Drive?" Do you mean, the starter engaged all by itself when you were in drive? Please clarify.

Third on the list is the ECM. Now I know sensors can get hot & fail, and then will allow a restart if they cool off. But my car restarts immediately - suggesting that it might not be a temperature issue. Would this add weight to it being the ECM?
We can't rule out the ECM, but I'm the last one to blame it first off. Most times when people change the ECM, they spend X-# of dollars just to find out that's not the problem.
Finally. Would the Mem-Cal code show up as a result of the CAM sensor we already know is bad? Or could there a bad mem-cal? (Is that even a real part?)
Mem-cal, is a function inside the ECM. That's why we can't rule the ECM out just yet.

I hope I don't sound dense or slow here.I realize the crank is the most common, but I'm still not getting whether or not the codes that showed up are more likely related to one possible cause over the other.

Thanks for your patience!
Chris
I would change the cam sensor first, clear the codes, drive it and see what, if anything, comes back.

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Saturday, March 14th, 2009 AT 4:47 PM

JAMES W.

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Just checking to see if my response came through.

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Saturday, March 14th, 2009 AT 9:17 PM

CHRIS C

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Oops - I almost missed your answers in my post!

I'll see if I can answer your questions/comments.

When I got the crank sensor replaced last June, it cost around $50 for the part and 1.3 hrs labor. My car had similar symptoms, but that time it had to cool off before restarting. When we got it to die again at the mechanic's, it died long enough to confirm that was a bad part. Therefore, that diagnosis made sense.

Things that make me question whether it's the same thing again:

1. No cooling time required before restarting
2. Would it cause a mem-cal error?
3. Would it cause a PRNDL code?

When I asked about the ignition module, I was speculating about whether or how that could be related to the PRNDL code.

That code indicates there was an attempt to start the car in something other than park or neutral. But I never did that myself. So what made the code come up? I wondered if a crank sensor, or ignition module, or ECM would try to turn itself back on again immediately after failing - thus causing that PRNDL code to show up. Which part is most likely to set this code?

Yes, I am *this* close to just changing the crank sensor again, but these things are holding me back:

1. Problem is so intermittent, it's conceivable I'd have to drive it for months before knowing if it was solved.
2. Cash shortage - I have 150 a month in 'spare' cash.
3. I cannot seem to get confirmation that these codes are logically related to this part.

Finally. When you said "I would change the cam sensor first, clear the codes, drive it and see what, if anything, comes back" did you mean crank sensor? Or did you mean I should fix a known issue (cam sensor) and get it out of the way in case it's adding confusion to the unknown issue?

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Sunday, March 15th, 2009 AT 4:38 AM

JAMES W.

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The ECMs from year to year are pretty much the same. The major difference is the Eprom used. The Eprom is the encoded program that the ECM uses to make it's calculations. The Eprom takes into consideration the vehicle weight, engine size, tire size and altitude to name a few.
If you "know" the cam sensor is bad, change it. Clear the codes, and see what comes up next. IF, the cam and crank sensors are both causing problems you can get phantom codes set that are actually unrelated, ie. PRNDL and mem-cal. Computer diagnostics is like peeling an onion. One step (layer) at a time.

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Sunday, March 15th, 2009 AT 11:30 AM

CHRIS C

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That all makes sense, and at this point you're right - it would be good to clean up the known stuff.

On the CAM sensor, I've been wondering something.

I was told (and read) that there's a little basket thingy that holds it in place, and if the basket thing came off, you'd have to open up all the timing stuff to get to it - and then, as long as you're in there, you should replace the timing chain and all that (thus upping the price of the job.)

Now. If the basket thing DID fall off, why can't you just leave it where it is and get a whole new basket thing and just stick it all on where it goes?

Hope I"m not wearing out my welcome.I really appreciate your insights!
Chris

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Sunday, March 15th, 2009 AT 7:04 PM

JAMES W.