Dreaded "Reduced Engine Power" issue

[tigers2007]

What part is it your referring to?

I’m referring to the actual sensor on the throttle body. What year is your truck? GM has had a lot of issues that go back from 2003 to 2012. Some people spend the $110-170 for a new entire throttle body assembly. The sensor kit is about $28. Takes about 15 min to replace.


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[ifixedit]

Hi all,

 

I haven't been on this forum for a long time but got an email notice this morning that this old thread has suddenly come back to life. 

 

A couple of things I've learned since originally posting this that may also help.  In addition to all I've listed to go through and check, the grounds being one of the more important to check, in particular the ground on the frame under the drivers door and the one on the back of the drivers side cylinder head (very hard to see and you have to feel around to find it), the other issue is the throttle body itself.  Here's what I've learned that is also at issue.....  There is what they refer to as a wiper inside the the throttle body under the black cover where the plug connects and basically the guts of the throttle body with the gears and so on reside.  Basically there's a small plate inside with electrical contacts on it that wear out over time, causing the signal to jump erratically from the contacts hence throwing the truck into reduced power mode because the computer is getting errant readings as to the position of the throttle body.  Auto parts stores such as Advanced do now sell a repair kit for the throttle body and I've seen a few videos online outlining the fix but my 2 cents worth is I wouldn't touch it with a 10 foot pole.  The answer if you've exhausted all other possibilities and it is still happening is to replace the throttle body with a new 'quality' unit.  Beware of the cheap made over seas by the CH-ina company units, don't waste your money as they will last around 6 months to a year without issue and will be at it again, trust me I learned the hard way!  The last throttle body I put on my 03 was made in the USA, was about two years ago now and have not had one problem since.  At the time the factory replacement was an AC Delco but they were on back order and were impossible to find.  If you have a throttle body with a lot of rounds on it (i.e. lots of miles), find a good quality built in the US unit and your problem should be solved.  I don't remember the brand I ended up buying but it was US made and I got it at Advanced Auto Parts, they should still have them.

 

Hope this helps,

 

Marc      

[ifixedit]

Also as an add on here.  Disconnect the battery when replacing the throttle body and touch the battery leads together, this and the time taken to replace the throttle body gives the computer time to clear any codes stored, and you basically start from square one on re-connect and first start.  There are several procedures outlined online as to doing the throttle body relearn procedure, but I found the best way to do it is just start the engine and let it idle (don't touch the throttle) until it comes up to full temp 210 degrees.  Once you're at 210 put your foot on the brake, let it idle and put it in gear for a few, but don't let the truck move.  Put it back in park, still letting it idle and turn on the AC for a few, then put it in gear with the AC on and again keep your foot on the brake and just let it idle for a few.  After this take it for a normal drive and vary the throttle but don't go nuts at first and go drag racing.  At first the truck will be pretty poochy and will seem to not have a lot of power.  What's going on is it's re-learning as you drive and you will have to drive it for a few days as it re-maps everything.  After I drove mine a few days I began stabbing the pedal to the floor at various speeds and the truck began to come back to life in fairly short order.  It takes a number of these flooring procedures but again, all was back to normal in a fairly short period.    

 

If you want to try the throttle body repair kit vs. replacing the throttle body it's up to you, but again my 2 cents worth is I wouldn't especially if the repair kit is not US made.

 

Marc 

Edited January 14, 2020 by ifixedit

[Gtm]

The grounds that I am familiar with and addressed are on frame under driver's area and one each on back side of heads next to firewall (tight location). I was able to reach and disconnect, clean and tighten. This is where my problem was found.  

My reduced power made my truck crawl at 5-10 mph at 1000 rpms. It only got better by clearing code until next code being triggered by lose ground. 

Your problem is probably different but I would definitely check your codes. 

[03chevyhd]

2 hours ago, tigers2007 said:

 

I’m referring to the actual sensor on the throttle body. What year is your truck? GM has had a lot of issues that go back from 2003 to 2012. Some people spend the $110-170 for a new entire throttle body assembly. The sensor kit is about $28. Takes about 15 min to replace.


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It's a 2002 1500hd 6.0

[03chevyhd]

2 hours ago, Gtm said:

The grounds that I am familiar with and addressed are on frame under driver's area and one each on back side of heads next to firewall (tight location). I was able to reach and disconnect, clean and tighten. This is where my problem was found.  

My reduced power made my truck crawl at 5-10 mph at 1000 rpms. It only got better by clearing code until next code being triggered by lose ground. 

Your problem is probably different but I would definitely check your codes. 

Ok thanks I'll check those out and see what I find. Thank for the help! 

Edited January 14, 2020 by 03chevyhd

[03chevyhd]

2 hours ago, ifixedit said:

Also as an add on here.  Disconnect the battery when replacing the throttle body and touch the battery leads together, this and the time taken to replace the throttle body gives the computer time to clear any codes stored, and you basically start from square one on re-connect and first start.  There are several procedures outlined online as to doing the throttle body relearn procedure, but I found the best way to do it is just start the engine and let it idle (don't touch the throttle) until it comes up to full temp 210 degrees.  Once you're at 210 put your foot on the brake, let it idle and put it in gear for a few, but don't let the truck move.  Put it back in park, still letting it idle and turn on the AC for a few, then put it in gear with the AC on and again keep your foot on the brake and just let it idle for a few.  After this take it for a normal drive and vary the throttle but don't go nuts at first and go drag racing.  At first the truck will be pretty poochy and will seem to not have a lot of power.  What's going on is it's re-learning as you drive and you will have to drive it for a few days as it re-maps everything.  After I drove mine a few days I began stabbing the pedal to the floor at various speeds and the truck began to come back to life in fairly short order.  It takes a number of these flooring procedures but again, all was back to normal in a fairly short period.    

 

If you want to try the throttle body repair kit vs. replacing the throttle body it's up to you, but again my 2 cents worth is I wouldn't especially if the repair kit is not US made.

 

Marc 

Hi Marc 

I've enjoyed reading your write ups, I really appreciate all the info. I'll look and see what I find and hope it's nothing too bad. 

Thanks! 

[ifixedit]

No problem, hope what I've provided helps.  I did a little research and was actually a bit wrong about the last throttle body I bought at Advanced Auto Parts.  It's a Techsmart and is actually made in Mexico, not the US.  They  also had an option at the time for yet another made in China unit but after all the bad luck I had with them, even though they were considerably less $$ up front, I spent the $200 + on the Techsmart and it's paid for itself so far, zero problems with it.  I also recall they had a good warranty on them if it were to fail.  They also now have an AC Delco reman but I tried one of them as well and it lasted like 6 months and I was under the hood again.  As for fixing the one you have, they do have a repair kit available as well but it will take more than 15 minutes to do the job.  The throttle body will need to come off, then you have to drill out the rivets that hold the black cover in place, then hope to repair it without messing anything up, put it back together and get everything right.  I pondered that option and decided against it. 

 

Marc

[tigers2007]

It's a 2002 1500hd 6.0

Wow I didn’t think that GM used the electronic TB in MY2002. Funny as my Tech 2 asks me if it has the electric throttle for my 2002 6.0 2500HD.

Your part numbers from RockAuto are:
17113659 for the entire assembly $250ish (with RPO NW7)
17123852 for the sensor without RPO NW7 $32 (TH149 at big box stores)
17114566 for the sensor with NW7 $53 (TH298 at the big box stores)

That has got to be a first generation LS electronic throttle as it looks huge. I’d started with the sensors. Maybe even from your local big box store so you can return it easy if it doesn’t fix the problem.
If you do order from Rock don’t forget to use a 5% off coupon code.


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[03chevyhd]

21 hours ago, tigers2007 said:

 

Wow I didn’t think that GM used the electronic TB in MY2002. Funny as my Tech 2 asks me if it has the electric throttle for my 2002 6.0 2500HD.

Your part numbers from RockAuto are:
17113659 for the entire assembly $250ish (with RPO NW7)
17123852 for the sensor without RPO NW7 $32 (TH149 at big box stores)
17114566 for the sensor with NW7 $53 (TH298 at the big box stores)

That has got to be a first generation LS electronic throttle as it looks huge. I’d started with the sensors. Maybe even from your local big box store so you can return it easy if it doesn’t fix the problem.
If you do order from Rock don’t forget to use a 5% off coupon code.


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I really appreciate the parts info and I'll just need to make sometimes this weekend to look at connections and grounds then work my way up. 

I think this happened because I was stomping on the gas because I liked the way the truck sounded while driving. It might not have liked that so it could be the throttle or the pedal. But as of now I'm just taking it easy. 

Thanks again.

Oh shoot I'm sorry I meant to write 2003 1500hd 6.0 lol my apologies!

Edited January 15, 2020 by 03chevyhd

[Gtm]

You might be onto something there about "stomping on the gas". 

[03chevyhd]

8 minutes ago, Gtm said:

You might be onto something there about "stomping on the gas". 

Lol yea 

[tigers2007]

Well if the TPS is bad, rapidly moving the butterfly could easily cause a fault as the electric stepper motor position is not in alignment with what the TPS is reading thus causing a fault - reduced engine power for safety. Basically to prevent an MCAS issue lol


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[Mighty]

I have a 03 Silverado hd and mine says reduce engine power I replaced the whole throttle body and still goes in limp mode ?

[Mighty]

I have to shut my truck off for a few seconds then it runs good til it happens again