2003 Envoy, Reduced Engine Power Lamp

deutzmann

Original poster
Member
Dec 31, 2014
10
Hi,my 03 envoy was driving just fine till about 7-8 days ago my check engine light came on ,then tonight i was driving a couple miles from home i had gone to my son house ,which is 9 miles from me ,then i retruned back home i was 2 miles from home an Reduced Engine Power ,light came on an i couldnt go over about 30 mph but i shift to 1 gear up the hills an got home ,can someone tell me what it might be ,TPS, Throttle Body ,Maf sensor ?? thank You ,this envoy has 231,000 miles on it i just replaced the transfer case, after the organial one clutch pak came apart an wore a hole in the side of case ,i put another used tr case on an everything was working fine, now this ,i do need to give it a tuneup ,any ideas,thanks
 
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Mounce

Member
Mar 29, 2014
13,667
Tuscaloosa, AL
deutzmann said:
Hi,my 03 envoy was driving just fine till about 7-8 days ago my check engine light came on ,then tonight i was driving a couple miles from home i had gone to my son house ,which is 9 miles from me ,then i retruned back home i was 2 miles from home an Reduced Engine Power ,light came on an i couldnt go over about 30 mph but i shift to 1 gear up the hills an got home ,can someone tell me what it might be ,TPS, Throttle Body ,Maf sensor ?? thank You ,this envoy has 231,000 miles on it i just replaced the transfer case, after the organial one clutch pak came apart an wore a hole in the side of case ,i put another used tr case on an everything was working fine, now this ,i do need to give it a tuneup ,any ideas,thanks
No check engine light? Just reduced power?

Btw, don't be shocked if your post magically turns into it's own thread, a moderator might move it, you'll get better help that way.
 

deutzmann

Original poster
Member
Dec 31, 2014
10
sorry, i forgot to ad yes,, check engine light,, as well as,, reduced engine power,, is on now
 

Mounce

Member
Mar 29, 2014
13,667
Tuscaloosa, AL
Step #1 would be getting the codes read. Without the codes, we cannot help you.

If you don't have a code reader, local auto part stores like auto zone, advanced auto, oreilly's, etc will read them for free. Just go in and tell them you need your codes read and write them down when they tell them to you so that you can report them back to us without forgetting them.
 
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IllogicTC

Member
Dec 30, 2013
3,452
I moved the topic to document this separately from the previous issue. If you get the codes read, be sure to post them here. I and some others have access to data on places like alldata, and can give detailed information on what to dig into. We also offer a range of service manuals, offered free of charge by mooseman, found in this thread. They're in PDF format. Feel free to download the set, it also offers some insight into specific trouble code meanings and there's a ton of information on fixing things.
 
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Mar 15, 2012
45
After having this issue with my '03 Envoy, the site can help you. There are a couple of posts out there for the Reduced Engine Power (REP) light and causes. The codes are important and basic testing with a multi meter may help. I was able to pinpoint the suspected problems with help from MMAY03 and Roadie and others. Although I was able to identify the PCM was bad and I replaced it and the throttle body, I still had the issue. It cleared up and came back. I think I still have my notes from when I was dealing with mine to try to help you out. I would look over the posts on the site for this issue with a forum search for "REP" or "Reduced Engine Power" for research.

My ultimate solution ended up being the throttle body pigtail. I ended up having a dealer fix it as I was not confident I could replace it correctly and have a working truck.
 

gojeda

Member
Mar 4, 2015
8
Can you elaborate on what the throttle body pigtail is? Do you mean the harness full of wires that clamps onto the throttle body sensor/motor?
 
Mar 15, 2012
45
Wow. I am sorry, I have been out of touch for the last week or so. Had to do some repairs on my Envoy and working. If this is still relevant, yes. It is the portion of the wiring harness that plugs into the throttle body and joins the wiring that connects to the PCM.
 

deutzmann

Original poster
Member
Dec 31, 2014
10
Step #1 would be getting the codes read. Without the codes, we cannot help you.

If you don't have a code reader, local auto part stores like auto zone, advanced auto, oreilly's, etc will read them for free. Just go in and tell them you need your codes read and write them down when they tell them to you so that you can report them back to us without forgetting them.
Hi, iam back with more questions iam having 03 envoy 4.2 engine runs rough I, went an bought a Bosch OBD 1150 code reader it is giving me a code of PO306 cylinder 6 misfire detected ,I replaced it with a new coil an all new Bosch spark plugs,but it did"t make a difference in better running so I moved the coils around an it is still giving me the same code even after eraseing the codes an disconnecting the battery I had disconnected battery both + an = cables so it has to be something else I think ,,,what do you suggest ???
 

deutzmann

Original poster
Member
Dec 31, 2014
10
Hi ,I forgot to mention I had taken throttle body off an cleaned it with Amsoil Power Foam it cleaned up real good ,, Thanks Everybody for your help!!!
 

Mounce

Member
Mar 29, 2014
13,667
Tuscaloosa, AL
Check compression on cylinder #6. Likely lost compression or fuel. If you've got good compression and plug comes out wet with fuel then maybe you've got a bad wire going to the coil which would be best case scenario at this point. Worst case is loss of compression.
 

deutzmann

Original poster
Member
Dec 31, 2014
10
Check compression on cylinder #6. Likely lost compression or fuel. If you've got good compression and plug comes out wet with fuel then maybe you've got a bad wire going to the coil which would be best case scenario at this point. Worst case is loss of compression.
Hi, I did check resistance on each injector an they were all in tolerance cylinder # 4 was 12.2,ohmsthey other 5 were 12.4,12.5 my book said 11-14 ohms cylinder # 6 spark plug was wet when I removed it it definitely was getting fuel so now I will do a compression test ,it still is giving me a code of cylinder # 6 misfire,so I am wondering if it is not maybe a wire problem,,,
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
This video is very good for just this problem if you're not getting proper voltage to the coil:

 

deutzmann

Original poster
Member
Dec 31, 2014
10
Thank You Mooseman, i appreciate this very much i watched the video you posted 2005 trailblazer 4.2 #6 misfire i will be doing this test an see what i find .,i am thinking i might find the same issue maybe , i am working on this vehicle as i find time so bear with me i will get to the bottom of the problem so Thank You again for this info an i will make a donation to this site as this has been so helpful to me !!!!!
 

deutzmann

Original poster
Member
Dec 31, 2014
10
Hi, I just got done checking my # 6 coil an i am getting 12.37 volts with key turned on so i think its getting power ok ,i then started it up with engine running an checked it again while running an it was 14.36 on power to coil an on center wire i had from .6-.8 volts, i am not sure what these values should be ,,so i plugged wire back into coil but it did not make the engine run any better ,so i now need to go deeper yet .
 

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