alxsml

Hello everyone,


I have a 2001 Suburban 1500 that has been been malfunctioning since May 2012. It has been to three different shops, been to the last one 4 times and this last time they have had it for over a month STRAIGHT. I am also close to $2000 out on it and the problem is still not fixed.

I would be happy to list out all the symptoms and various resolutions these shops have come up with through the months, but that will make for a VERY long post - so I think I'll start with what I *think* is the most relevant info and go from there.


In a nutshell, they determined that the ECM was chewing up the crankshaft sensor - actually sending a spike of voltage and causing the sensor to fail over and over. On the third crankshaft sensor now and they recommended replacing the ECM. I opted for a brand new ECM just to get the 90 day warranty. The shop then had to take it to the dealer to get the ECM programmed. They put it in and now are having other injector sensor issues. Last time I talked to them, they said that there is something else within the electrical system of the car that is chewing up (shorting out) the ECM! I also think they are on the third ECM now! Like I mentioned earlier, the car has been in the shop for over a month - and they are "on the phone with StarTech (sp?) everyday" trying to get this fixed. I am told that StarTech is some kind of GM top level tech support for tough cases like this. I googled it and don't see any relationship between StarTech and GM so this is why I don't know if I am spelling it correctly.

In my opinion, I am getting the best of both worlds because I am not paying dealer prices, but at the same time am getting dealer service, but I am posting all this just to see if anyone smells anything "fishy" here. Is it reasonable to expect the dealership to be able to test all electrical wiring in the car within a few days? I feel like my car is getting bumped to the bottom of the priority list just because it is a difficult problem and they full well know that I really do not have any other options.

Like I said, I would be HAPPY to list a detailed timeline of all symptoms and resolutions through the months - if anyone is interested.

Any thoughts on this will be much appreciated!

Thanks everyone

kevinkpk

ECM's are about the last suspect thing. The misfire certainly could be something else. The CPS works as such, It has a reference circuit to, and from it to basically check continuity, or that the ecm or pcm whatever knows it is there. This is the one part (I delt with industrial gas turbines) I am not sure if that circuit powers the probe, I doubt it as it has a magnet. The cps reads and developes a sine wave sent to the ecm as a "speed" input for calculations. The magnet reads a "cog", gear whatever The ecm is programmed to know how many of these to calculate the hertz/speed. The faster the crank, cam whatever turns the higher the frequency, and voltage amplitude, that is fed into the ecm, it determines based on what it is programmed reads this eventualy in laymans terms as rpm's.

To say the ecm is chewing up cps is, well really hard to believe. Is there any codes, and is this always just related to the cps? The misfire could be injector or ignition. My advise (if I where the dealer) fix one at a time.

alxsml

Would it be possible that an external short circuit of some sort in the general electrical system could possibly be destroying the ECM? Has anyone EVER seen this happen?

MDTAHOE

I find it very hard to believe the ECM was bad at all. They almost never fail. I think you need to take it somewhere else.

alxsml

Okay well maybe I should give you guys an idea of the hell I've been going through these past few months with this thing. I'll try to keep it as short as possible

ORIGINAL PROBLEM

Suburban stutters on gears 3 and 4, and especially going up hills, while loaded up with a lot of cargo and when it warms up. NEVER any problems in gears 1 and 2. The RPM need drops down sharply when this happens. At slow speeds, I have had it stall out completely, but it ALWAYS starts up perfectly fine without a blip.

First shop (back in May) had me replace all spark plugs, spark plug wires, cleaned the injectors and cleaned the fuel pump. Was fine for about 2 weeks and then started acting up again. They then said they were able to see the crankshaft sensor malfunction. They replaced this and it was fine for 2 weeks again.

Then took it to the dealer. They drove it for a week and were not able to reproduce the issue.

Then took a 1000 mile road trip - acted up immediately. This is when I realized it only acts up when the car is heavily loaded up. We limped through the whole trip as we did not want this ruining it.

Got back and took it to AAMCO as I was convinced this had to be a transmission issue. They were able to test the transmission and determined it was 100% fine. They then said that they saw the crankshaft sensor fail as well as the neutral position sensor. I tried telling them that the first shop had already replaced the CPS, but all they could say is that it was failing, and they did not originally do the work so they could not trust the first shop's expertise. They replaced these two. It was good for about 3 days and then it acted up again.

Took it back and they said they must have put in a defective neutral position sensor so they replaced that. Was good for 3 days again.

Took it back and now they saw the crankshaft position sensor fail again! They then replaced that in house and this is when they allegedly saw some sort of spike coming out of the ECM that is suspected to be chewing up these sensors. I authorized them to replace the ECM, which they had to take to the dealer to reprogram - and this joins up with the beginning of my original post.......

So after all this, is it still unreasonable to suspect the ECM?

alxsml

Latest on this. Yesterday I get a call saying that the dealer finally seems to think that they have everything figured out. It comes back to the AAMCO shop and they do some more intense road testing before giving me the go ahead. Well whaddya know? Car does the same EXACT thing as the original problem.

So ..... 4 months, $2000, 3 Crank Position Sensors, 2 Neutral Position sensors, 3 ECMs later - not a darn thing is fixed.

Supposedly AAMCO is bringing out a "super technician" on monday to take a look at it.

I need help!!

73shark

Not sure why one would go to a tranny shop for the kind of problems you seem to be experiencing.

alxsml

Well I took it there because the problem never shows up in gears 1 and 2 - only 3 and D. So this made me think it was a transmission issue. I was actually very surprised when they told me it isn't.

Are there any other components in the drivetrain that only engage in gears 3 and D?

kevinkpk

Iv'e backed off of this as I look at electrical schematic for this year/model range showing a single CPS. My 96 lumina has two cps one for 2000 rpm and below, and another for higher than 2k rpm.

alxsml

Thanks for taking the time to look through this Kevin. I really think the key to this whole puzzle is to figure out what component in the vehicle is supposed to engage in gears 3 and 4.

Looking through various forums/articles, I see that the TCC or TCC solenoid only comes into play in gears 3 and 4, but symptoms of a bad TCC seem different than what I experience. Thoughts anyone?

I also have a problem with my e-brake. It refuses to disengage unless I put it in reverse and drive for about 10 feet. Can this have anything to do with anything?

As you can tell, I'm grasping at straws!!!