Dealer Throwing Parts At My Truck?

outnumbered · July 1, 2010

New to forum here and I have a problem. I just bought a 2002 Yukon XL Denali with the 6 liter and 70,000 miles. I bought it with no warranty and am having problems with it. We have an intermittent serious hesitation that we can't pin down. The first shop my wife went to when it left her stranded put in new fuel filter, and the said that we needed a fuel pump. Since he couldn't be sure, I told him I'd do it myself. She drove it home the 100 miles and it had no problems. Then it came back and I took it to my local dealership hoping they would know what it was. They had a code for MAF sensor, so I had them change it, run a motorvac flush, and they put in another new fuel filter. We made it 20 miles and it threw a SES code, and then the hesitation hit about 100 miles later. Took it back to them, and it had thrown a code for the crank position sensor and P0430 for the right bank cat. The problem I have is that according to the records at the dealer, this truck just got a new cat in November 09 on the right side, and June 09 on the left. They put in a new one on the right side under warranty and said that it's fixed. What makes a cat go out in less that 10k miles, and does anyone have any other ideas what could be causing this problem??

Stevens03 · July 1, 2010

A bad Crank shaft position sensor could cause it to run bad. Bad o2 sensors could cause the cats to have a short life. Is the MAF sensor the correct one for your truck or not?.

gmtech121 · July 3, 2010

I'll tell you what.... If I diagnosed a failed ckp sensor while replacing the cats under warranty and the customer declined the ckp sensor? If the cat failed again due to the customer not repairing what was wrong with the vehicle..the customer would be buying the next set of cats. It's like throwing a rock through a window and blaming the window. Replace the friggin crank sensor.

outnumbered · July 1, 2010

A bad Crank shaft position sensor could cause it to run bad. Bad o2 sensors could cause the cats to have a short life. Is the MAF sensor the correct one for your truck or not?.

I decided NOT to do the crank shaft position sensor yet since it was running so bad, I thought that was what threw that code. As for the MAF being the right one, I sure hope so, but I did not check since it was the dealer and factory parts. Would the o2 sensors throw their own code, or are they combined within the P0430 code? I bought a code scanner to keep a better eye on it for myself, and if this comes back AGAIN, I'm going to another shop. I just find it odd that both cat's have been replaced and I'm having trouble again leads me to believe it is something else causing it to run out of spec and burning up the cat.?? I'm no tech, but that's my thinking.

Stevens03 · July 1, 2010

Well a bad crank shaft position sensor will cause it to run horrible. If thats what it's doing, I'd certainly consider it. I do believe the o2 sensors throw their own code. A buddy and me just did a motor swap on a dodge and the sensor was bad there. We swap it out, and she purred like a kitten. I couldn't believe it caused so much trouble.

outnumbered · July 3, 2010

I'll tell you what.... If I diagnosed a failed ckp sensor while replacing the cats under warranty and the customer declined the ckp sensor? If the cat failed again due to the customer not repairing what was wrong with the vehicle..the customer would be buying the next set of cats. It's like throwing a rock through a window and blaming the window. Replace the friggin crank sensor.

gmtech121, What I WATCHED my service writer do on ATTEMPT # 2 to "diagnose" my truck was to plug in a scanner, read the same codes I already knew of, and tell me within ONE MINUTE of "diagnosis" was that I needed a new cat and ckp sensor. My question to him and what I was trying to find out here is, What common items can cause these 2 items to fail, or show a DTC code? IF my truck throws a code for the CKP, then fine, I'll put one in if needed, BUT for the week that I waited for the new cat to come in, the truck continued to throw P0430 code every day, while never again throwing the code for the ckp sensor. I know that you did not have the complete story while replying to this thread, but your defense of this dealers "diagnosis" seems to fit along with what I am dealing with at this shop. The was no "testing" done except for pulling codes, hence the title of this thread. They threw in a MAF hoping this would fix the problem, now a cat, and maybe next a ckp sensor, but never once looked into WHY they went out.

gmtech121 · July 3, 2010

and I believe (from here at least) that the maf was probably misdiagnosed. What I'm telling you is an intermittant ckp sensor will cause a cat failure. What motive would I possibly have here? What ckp sensor dtc was set was also not mentioned. There are a few. There also isn't a whole lot a technician can do to diagnose an intermittant ckp sensor signal. Popular opinion is that you just "put it on the machine" and it tells you everything. It doesn't work that way. Sometimes years of experience (which yes... does include some trial and error) leads one to most probable solution. If I have something acting up once a month on a tuesday evening while turning left with a westerly wind...what exactly can one do. If it's working when you test it.. it's gonna pass. A ckp signal is the heartbeat of a running vehicle. They're about $50 in most cases...they're a higher than average failure item...

All I'm saying is if it were mine... I'd replace it.

outnumbered · July 3, 2010

The code for the CKP I do not know. What I do know is the my service writer somewhat unhappy to see me back after charging me $750 for work that did not fix the problem grabbed a handheld scanner from a tech and scanned the codes. He did not tell me the exact #'s, but after some discussion, we decided that the ckp might have been caused by the sputtering and crappy running of the truck during it's last fit. I have since purchased my own scanner, and it has onlty thrown the P0430 code several times. My wife picked up the truck a couple of days ago, and I am away from home for 2 weeks, so we'll have to see if it continues to act up. No offense meant in my last post, I'm just trying to find out if there is some condition that they may not be looking at. I understand the problem with intermittent issues, that's why I'm here asking questions.

txab · July 3, 2010

Replace the CKP

green 788 · July 3, 2010

The crankshaft position sensor went bad on my wife's '97 LHS (Chrysler)... and the car would stutter, and sometimes totally shut down.

The cat never clogged up, though... but replacing the sensor fixed the problem which had been going on for a while.

Two different animals (1997 Chrysler 3.5 engine and your motor), but the sensor could be your problem. Wiring to the sensor should be check also.

Dan

gmtech121 · July 3, 2010

Catalytic converters don't really go bad. They are murdered. I've spoken to enought engineers over the years about it.

It takes a whole lot less misfires than you would think to overheat and damage the substrate in a cat. You can replace cats all day long... if whatever is causing the lean condition or misfire is not repaired.... more cats will die.

Maf codes are often not set by a failed maf. THey are performance codes... not circuit codes. Basically it just means for a given rpm and load... it doesnt seen the airflow it should. An example would be a restricted cat will often set a maf sensor code. On those particular vehicles an o2 sensor will almost always set a dtc long before it will cause driveability issues

As far as ckp sensors... that's kind of the hearbeat. You need to go after a ckp sensor issue before anything else. Of course that doesnt always mean sensor... there's wiring and pcm to consider as well.

outnumbered · July 3, 2010

I get what you are saying about testing parts first before replacing them. I would THINK that my dealer would try that method, but they instantly wanted to put a CKP sensor in because it threw a code for it. I can put parts in no problem, what I want is some testing to be done. If the cat fails again, at least it will be under warranty. Meanwhile, I will talk to my other local dealer and hope they have a better service department. What I am really looking for are common problems that will send the type of codes that I am getting, and cause intermittent misfires and a crappy running truck.