I need a smart GM mechanic's help

[ericinmich]

Re: I need a smart GM mechanic\'s help

Another thought about what happened with your trip to the dealer.

When the dealer plugged in the tech tool to look at codes stored, there may have been a code set that indicated the converter was bad. The catmon (catalyst monitor) diagnostic uses the signals from the front and rear O2 sensors to monitor the efficiency of the catalyst. So you could of had:

1. A truely failed converter. Not plugged (enough) to impact engine airflow, but bad enough to fail the monitor.
2. The previously changed O2 sensor could of led the VCM to think that the coverter was bad. The fail code would of been in history, but still reported out to the tech tool.
3. The new O2 sensor could be enough different than the OEM one to falsely fail the convertor diagnostic. We have seen this before, but it's probably not likely.

In the end, diagnosing these proglems are not easy. We're trying to make the systems 'smarter' and more sefl diagnosing...

 

[JimR]

Re: I need a smart GM mechanic\'s help

I too wish it was that easy to read and fix these electronic problems. The converter was clean as a whistle. I still have it abd you can see right through it. There is absolutely nothing in it to block it off in any way. What I think the service writer did, was to tell the mechanic that I was complaining of no power. He should have told him that it was on hills. He in turn dropped the exhaust and saw he could redline it. Then automatically asumed it was the convereter. The truck would redline in first gear on flat ground. That surely is not a sign of a plugged converter. I haven't worked on cars for a living since 1980. I found the EGR problem. They couldn't find it. Had I been average Joe. I wonder just what this really would have cost me if they had done the repair work. How much of it would have been switching parts till they found the real problem. Back when I was working as a mechanic we changed parts out also. But we didn't leave them in the car if it didn't fix the problem.

 

[JimR]

Re: I need a smart GM mechanic\'s help

KAB,

The parts store code reader did say the Bank 1 # 3 02 sensor was bad. The dealer's reader did not pick up a code. I just got off the phone with them and the mechanic. They called me an apologized for the error in diagnostics. They also offered to run a free diagnostics on the EGR problem to find out what is really wrong with the truck. He also stated that they would not have charged me for the converter if it had not solved the problem. Sometime around Thanksgiving my truck will be home again. I will then contact the dealer to have them fix it.

 

[TCBoomer]

Re: I need a smart GM mechanic\'s help

Jim

I'll save you the additional diag expense and the inconvience that your son may have to deal with while at school and trying to get it fixed.

With about 98% certainty, you have a shorted FTP sensor...Fuel Tank Pressure Sensor. Check the schematic in your manual and you will see that it shares the ground and 5V ref circuits (S102 & S101 respectively) with the EGR. To prove it's the cause, reach up on top of the fuel tank and unplug it. It is slightly difficult to reach...but can be done. Reconnect the egr and drive it. You'll see!!

BTW...The shorted sensor will NOT set a code.

If you would like, I can explain in much more detail regarding the why's and how's. Including what most likely occured at the dealer.

PM me if you'd like

 

[Bird]

Re: I need a smart GM mechanic\'s help

Sounds to me as if the dealer is doing all they can do under the circumstances.

 

[HGM]

Re: I need a smart GM mechanic\'s help

Jim,
I too disagree with the blasting you gave the dealer. Dont get me wrong, I spent 15yrs in dealers as a tech and dont have much love lost.

The reason I disagree is that I have been on the other end, it is easy to get the scenereo that you layed out about the svc. advisor diagnosing it on the drive. The dealer would have fixed it anyhow, being knowledgible as you are, it likely wouldnt have cost you for the converter.

Now, let me add another idea to the fire....

The parts store told you the downstream O2 was bad. What this means is the converter isnt converting /forums/images/graemlins/grin.gif. If the converter becomes chemicaly inactive, the rear O2 will switch like the front and set a code. Being you replaced the sensor, if the tech was inexperienced, the only thing left is the cat.(follow me?) However, the cat will become chemicaly inactive in time with normal age, or if it is abused. A missfire will overheat and kill the cat relatively quickly.

Bottom line, looks like boomer has run into this before. I would definitly check the FTP out to see, it makes alot of sense. As for the cat, it may have been bad, you'll never know unless you reinstall it. I would be pissed at the parts place for selling me sensors I didnt need.

Just for future reference, if someone tries to sell you an O2 sensor or a PCM, be suspicious. They dont fail as often as you might think. Good luck, looks like your letter worked afterall. /forums/images/graemlins/grin.gif

 

[JimR]

Re: I need a smart GM mechanic\'s help

HGM,

I spent 10 years of my life working for dealers too. I remember a really nice used TR-6 one of these dealers sold to a very nice young lady. I also remember what we did to that car before she picked it up. The car was burning oil pretty bad. The mileage was under 30k on the car. We put 2 quarts of 30 weight oil in it. Plus 2 quarts of rear end gear oil and a quart (4 cans) of Winns motor additive. She came back after she had the oil changed 3000 miles later. She didn't have such a pretty face on. She had a letter from the garage that changed the oil. The dealer I worked for put a new rebuilt engine in her car for free. Ever hear of sawdust in a rear end to keep the ring gear from singing?

I did see the codes for the bad 02 sensor. It even stated which one was bad. I replaced all 3 of them. I still have the old CAT. It is not plugged and you can see right through it. None of the honeycomb is bent, melted or distorted in any way. I'm waiting for a reply from Boomer on the gas tank sensor.

 

[HGM]

Re: I need a smart GM mechanic\'s help

Yea, seen alot of that... Motor honey was popular with some guys. And yes, sawdust too, another one was reseating the rings of a running engine with a Commet/water mix poured down the carb. There are some dealers out there that have no bussiness be in bussiness. Theory is that you need to give them a chance becuase they know your product the best. Hopefully you get the tech that carries the dealer competancy, not the car was guy........

If the cat was inactive, you wont see the dammage..

 

[JimR]

Re: I need a smart GM mechanic\'s help

Baking Soda works well for seating chrome rings that won't seat themselves. I never heard of using Comet.

 

[TCBoomer]

Re: I need a smart GM mechanic\'s help

Hey Jim

I didn't get home till 2AM last nite and tried to reply, but couldn't keep my eyes open. I'm at work now, so sit tite and I'll get back to you.

Just a FYI...I am a 28yr+ GM tech and work at a GM dealer

Bob

>>>tried to PM this to you and it doesn;t sem to work???