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2002 chevy trailblazer_lt_ext
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3 Posts
Discussion Starter #1 (Edited)
Hi, new to the forums, although I lurked before finally joining. There is some great info here, it has already helped me a lot.

I decided yesterday to go ahead and clean the throttle body and replace the spark plugs, as my 02 TB EXT (125K miles) has been running a bit rough lately. I followed the instructions I found on the forum for removing the throttle body, and cleaned it thoroughly with throttle body cleaner. After I also replaced the plugs (with AC Delco 41-103s, .043" gap), I reassembled everything, and reconnected the negative terminal of the battery, which I had disconnected the whole time I was working on the vehicle (I also had to replace a burnt low beam headlight socket).

When I started the truck, I got the Service Engine Soon and Reduced Engine Power lights. I borrowed a code scanner, and the codes it shows are P0122, P1120, and P1220. From what I've been able to find, it looks like the codes are most likely related to the throttle position sensor. I've checked the wiring, and everything seems to be connected properly. Could my cleaning have damaged the TPS? I'd appreciate any suggestions. I'm still looking, so hopefully I'll find the solution soon, and it won't be too expensive :bonk:

TIA for any suggestions.
 

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2004 gmc
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26,181 Posts
Did you use carb cleaner, or specifically Throttle Body Cleaner? All I can think of if you used TB Cleaner is a broken wire inthe harness you can't see, from the flexing it gets during a cleaning. Or a bent pin in the male part of the connector. Did you disassemble it looking for bent pins?
 

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2002 chevy trailblazer_lt_ext
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Discussion Starter #3
the roadie -

I used O'Reilly's Carb and Choke cleaner. My wife went and picked it up for me while I was taking the airbox and resonator off (I used KHill's instructions). She said she asked the salesperson for throttle body cleaner, and she gave her that. I looked on the can before I used it, and it stated that it could be used for throttle bodies. I'll bet some got to the sensor, and screwed it up. I was very careful unplugging the wiring harnesses, and the wiring to the sensor didn't feel stiff or brittle when I unplugged it, so I think it's less likely that the harness is the problem. I'll search the forum to see how to test the wiring, to make sure I've got power going to the sensor.

Thanks for your help.
 

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2002 chevy trailblazer_lt_ext
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3 Posts
Discussion Starter #4
OK, I got a replacement throttle body, assuming that the problem was the TPS on the old one that I cleaned. I put the replacement on, and I'm still getting the SES and REP lights, with the same behavior at idle. I left the battery disconnected for a full 30 minutes while I put on the replacement body.

At this point, I need to find some info on how to test the TPS and the wiring to the TPS. I've searched and scanned over threads here, and Google, and haven't been able to find anything. I've found instructions on testing other model cars' sensors, but haven't found anything about how to test the TPS in the Trailblazer's throttle body, or the wiring. If anyone can point me to a thread or a web site with some instructions, I'd appreciate it. My next step is probably taking it to a shop to have it checked out if I can't figure something out pretty quickly.
 

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2004 chevy trailblazer_lt
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11 Posts
same problem here

yes sir thats what im doing tomarrow im finally takin my wifes blazer in i have all the same problems you got and ive doubled and tripled checked everything
 

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2004 gmc
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26,181 Posts
Yeah. Lazy ass unpaid volunteers like me have been doing nothing for five years but chatting about girlfriends, fantasy turbo projects, and what wax is the best for Indiana weather conditions. :rolleyes: :hopeless

Seriously, there are SOME very subtle and difficult faults that happen in this electronically sophisticated platform. And many members look for cheap and instant fixes and they don't want to hear that sometimes you have to take it into the dealer who has the TechII tool for a sophisticated diagnosis.

But I suppose if YOUR specific problem isn't already solved by others, it's up to YOU to solve it, and post up to help the community. I'll lay odds that trailvoy is one of the most successful problem-solving communities out there.

Oh, and the "SOLVED" tag is relatively new, and not everybody knows to tag their thread after they fix the vehicle. The first 80% of the threads on here were started without the tag being available. What lamers we were, fixing problems and not retagging the thread solved. :no: :weird: :hissy:
 

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Premium Member
2002 chevy trailblazer_lt
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708 Posts
:eek: :hahano: Ouch sorry he hit a nerve there Roadie. Anyhow maybe the OP should try resetting the codes first then go from there. It is most likely wiring burnt or bare somewhere that is unseen causing the problem. If need be after you have the codes reset go to the dealer as Roadie suggested and have it scanned.
 

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2002 chevy trailblazer_ls
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54 Posts
na im serious tho, people need to post up what fixed the problem if they have in fact fixed it. It would increase the chance of the people fixing the problem and not have to post new topics. :chillpill:
 

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2003 chevy trailblazer_ls
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264 Posts
Did you use carb cleaner, or specifically Throttle Body Cleaner? All I can think of if you used TB Cleaner is a broken wire inthe harness you can't see, from the flexing it gets during a cleaning. Or a bent pin in the male part of the connector. Did you disassemble it looking for bent pins?
I just used Seafoam on my throttle body Saturday. I had a bit of toruble with the wiring harness because the guide in the articles section doesnt mention the locking pin which is valuable information imo. Thanks for the tip. I will see if I can find a loose wire. I suspect I know which one it would be.

Odd thing is after the TB clean, the truck didnt run to bad that whole evening. Yet the next day, sunday, it ran like poo. It occasionally had a stutter in it almost like it was going to stall but never did.

Lets assume it is the main harness there by the tb..and if I cant get mine bent back in to place, would it be easy enough to go to the junk yard and grab me a whole new cable, or would I be better off chopping the harness off and putting a used one on there and then connecting the wires?
 

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2004 gmc envoy_slt_xl
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1 Posts
Help!!!!

I have a 2004 GMC Envoy XL V8 5.3L Truck and when it was about 20 degrees where I live while I was driving my truck it began to not shift into the next gear and it did not go over 50mph then the reduce engine power light and service engine light came so I drove it to auto zone to get it checked out it gave me these three codes P0128, P0220, and P0220 again. When I started the truck after leaving auto zone both the reduce engine power and service engine soon light were off and have not come back on but I have only driven the truck twice after that. I took the truck to GMC and they told me that I need to replace the Throttle body and the Powertrain engine control module which was gonna cost like $1600.00. I spoke to another mechanic and took it to their shop because they said it sounded funny that I needed a throttle body and powertrain engine control module at the same time and they put my truck on the testing machine and they said it gave them a lot of codes and they checked the throttle body and it was full of gunk and they cleaned it out and they said we will go from there to see if that was the problem first before paying all that money to get a new throttle body and replace the power train engine control module. I hope that the problem was solved by cleaning the throttle body but I am just not sure. Can someone please help me and tell me what to do or what my problem sounds like and what needs to be done? Thanks
 

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2008 gmc envoy_sle
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574 Posts
I have a 2004 GMC Envoy XL V8 5.3L Truck and when it was about 20 degrees where I live while I was driving my truck it began to not shift into the next gear and it did not go over 50mph then the reduce engine power light and service engine light came so I drove it to auto zone to get it checked out it gave me these three codes P0128, P0220, and P0220 again. When I started the truck after leaving auto zone both the reduce engine power and service engine soon light were off and have not come back on but I have only driven the truck twice after that. I took the truck to GMC and they told me that I need to replace the Throttle body and the Powertrain engine control module which was gonna cost like $1600.00. I spoke to another mechanic and took it to their shop because they said it sounded funny that I needed a throttle body and powertrain engine control module at the same time and they put my truck on the testing machine and they said it gave them a lot of codes and they checked the throttle body and it was full of gunk and they cleaned it out and they said we will go from there to see if that was the problem first before paying all that money to get a new throttle body and replace the power train engine control module. I hope that the problem was solved by cleaning the throttle body but I am just not sure. Can someone please help me and tell me what to do or what my problem sounds like and what needs to be done? Thanks
can you update your post please.

did the t.b cleaning fix your issue?
 

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2008 gmc envoy_sle
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574 Posts
perhaps you don't know but cars can't be fixed over the phone or on the internet. Perhaps you can do it though and I'm wrong on that count.
He is just venting his frustration.

I understand completely. His frustration is just misplaced. AS Its been a decade since these trucks were last made.

so considering the fact there minimum 10 years old (Including my own, 2008) . problems are bound to happen.
 
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