Dreaded "Reduced Engine Power" issue

[SpartanAutoworx]

I have owned plenty of GMT-800 trucks that had this issue. It has always been the Gas pedal for me.

[Adrian17]

my 03 1500HD with the 6.0 has done this mabey once ever month for about 3 months. Check engine light comes on and reduced power in the display. Would happen when I turn the truck back on from normal driving the problem seemed to have gone away on its own and has not done it for a good while (mabey 6 or 7 months).

[marissa]

I've been having an issue with my Trailblazer now for over 6 months with the dreaded "Reduced Power Mode," and "Stabilitrak Off" message. I've taken it to the mechanic over a dozen times and nothing seems to fix it. I'm desperate. The following codes keep coming up: P0121, P0171, P0174, P060E, P2135, P2138 The mechanic has replaced the Trottle Body Twice, the ECM, and the Pedal. The problem keeps coming back.

 

I need to take it to a different mechanic now and I have no idea where to start or what to tell them. I don't want to keep throwing parts at it or keep paying hefty repairs. I notice this issue became more frequent (or at least it seems like it's more frequent) when the weather is colder. I don't know if this is a wiring issue or what else it might be. I was just hoping that someone might be able to point me in a direction or at least help me figure out what I should suggest the new mechanic look at.

 

I'm wondering if ifixedit's solution might work.

Edited November 29, 2016 by marissa

[rcmedic]

Thank you Marc for the excellent write up. I have been fighting this battle on my 2005 Suburban 2500 4x4 LT for a little over a year now. True to claims, it has been intermittent. I long since replaced my knock sensors and the throttle pedal position sensor. Also true is the fact that I replaced (first) just the TPS on the throttle body, then the plug and harness for the TPS and then with the entire new throttle body assembly. The problem has continued unabated and also continues to occur completely at random. Sometimes the interval is very short, (sometimes only seconds) and other times very long, ( 1000 miles or more). After replacing the entire throttle body assembly and NOT correcting the problem, I took it to a local dealer to put it on their computer for assessment and re-calibrating/relearning etc. and all that was a bust too. (dealer charged me $120). The dealer told me that they would have to replace all of the parts that I already replaced "with Genuine GM pars" or they would be unable to do anything never mind make any guarantees. (their estimate for repairs was well north of $1000). I said no. I have spent countless hours researching this issue and thus far to no avail. You bring up a single point that I have not investigated "closely" and so my next step will be to address the grounding connections. Though I no longer do it for a living, I have been a mechanic virtually my entire life. Your detailed instructions are very good. Thank you.

 

On a separate note, I have been needing some dielectric grease for some other projects anyway. Guess I will finally go buy some. Thanks again.

[rcmedic]

Here is another response from the Edmunds forum.

 

Don't pay huge money for diagnostics...please read!!!! I finally found someone that fixed my YXL and fixed it right...The problem is the ground wires. My mechanic tightened one that he found loose and the other one the clamp was messed up so the ground wire was flopping around and not making a good connection. When he touched the ground wire he could hear the fuel pump going on and off and other things making noises. It was a $3 dollar clamp that fixed it...too bad I spent almost $2000 on diagnostics with the dealership that was trying to tell me I had a bad transfer case module as well as a bunch of other BS and another mechanic before I brought it to this guy. Make sure your mechanic checks all the grounds (I didn't know that there's more than one) and tightens them as well as making sure the clamps are in good condition. My clamp was broken causing a bad connection. So...it's a $3 part that caused this hellified problem! I'm just glad to have my vehicle back in good running condition...no thanks to the dealership or GMC!

[ifixedit]

Hello Brad,

 

Thanks, I sure hope what I've written here helps as this is one of the MOST frustrating problems to solve on any vehicle I have ever owned, it's enough to drive you nuts due to its erratic nature!

 

Just in case you or anyone else has not seen this part on page 1 of this thread I've copied and pasted here.....

 

I had also reported earlier that I had used dielectric grease on all the connections, including the plug at the throttle body. Curious but the truck would mostly do it's "reduced power" thing either when it was very humid out or after it rained. I also reported earlier that I could just about predict when it was going to do it because I had a very pesky ignition static noise on the radio when it was on most any AM station, especially when I was near power lines, this static would also get worse when it was humid or after it rained and it was just about guaranteed the truck would go into reduced power mode. Well, as it turns out dielectric grease happens to have SILICONE in it which is notorious for ATTRACTING moisture! Go figure! I came to the conclusion that all these codes were more likely the result of either moisture OR the grease itself allowing the signals / power to possibly jump around from one pin to the next at the throttle body connection and that possibly just a good dry connection would be better. I proceeded to unplug the connection at the throttle body, got out a can of parts cleaner, sprayed it on all the plug terminals, including on the TB itself, then thoroughly blew both connections out with my air gun to completely remove the dielectric grease. What happened? Truck runs like a million bucks again and no static on the radio! I've come to the conclusion, the dielectric grease is fine for the grounds, but DON'T use it anywhere else!

 

The above was the final solution to my problem, the truck has only done the REP once in over a year and it was when I floored it one day goofing around. I passed it off as the TB is likely now due to be cleaned and is sticking a little near full throttle which makes sense as if it is sticking a little there would then be a correlation error between the pedal and the TB which would certainly throw it into REP. In any case I haven't bothered to clean the TB yet and it hasn't done it again, so go figure. Also, it seems the plug at the TB has to be inspected for good connection and possibly in need of a routine cleaning from time to time to be sure it is absolutely dry and free of any oil or grease. Otherwise my truck now shows 245,000+ on the clock and continues to runs perfect.

 

Marc

Edited April 5, 2017 by ifixedit

[snowri]

Hello All,

 

I've been having similar P1516 issues once every few months, then once a month, daily and then several times last week. Until yesterday, I was unable to recreate my P1516 error.  I checked the TB plug, wires, grounds, gas pedal plug/wires, etc but could never create.  I was reading this string and thought to check the Throttle Actuator Control (TAC) which is mounted on the fire wall...  No issue with the plug that goes inside the cab but when I touched the larger plug, I immediately could hear the TB cycle then idle rough then REP.  The pins in the TAC and the female connectors in the plug looked shiny with no visible issues to the wires.  I did notice that some of the female connectors appeared larger (expanded) than others even though the TAC pins appear to be the same diameter.  

 

I took apart the plug and removed each female connector to inspect.  No discoloration on connector any so I don't think there was any current overload but when I used my carb jet cleaning tool, I did find that some of the connectors were slightly expanded perhaps due to vibration...   With the jet tool still inserted in each connector, I gently squeezed the connector smaller then rotated 120 degrees then another 120 degrees to keep it fairly rounded.  Again, this isn't a permanent fix but when reassembled, I've had no issues in the last week.

 

Does anyone know if this plug can be purchased?  

Thanks,
Scott

 

[Gtm]

Thanks to Ifixedit for his post back in September 2016. I have been looking for the fix to my u0107 code which is lost communication with throttle actuator controller module.  Unfortunately,  I replaced many parts to no avail.  Finally,  I checked all grounds and found passenger side head ground loose and dirty.  After everything that was done including throttle body, accelerator assembly,  pedal to tac harness,  tac, throttle body harness pigtail, removing all grounds (wire brush cleaning, dielectric grease and resecuring). The last ground being the one previously mentioned was the main problem found.  Thank you Mr. IFIXEDIT for taking time to post your experience and success. 

[03chevyhd]

Does anyone have the locations of the grounds that I would need to check? 

[Gtm]

12 minutes ago, 03chevyhd said:

Does anyone have the locations of the grounds that I would need to check? 

What is your problem? 

[03chevyhd]

30 minutes ago, Gtm said:

What is your problem? 

Same thing as described above, "reduced engine power" today was the first time that it happened. Went to turn it on about 20 mins later and power was good but check engine light was on. 

[tigers2007]

This part is in stock at your local big box auto parts store and also your local dealer. What year is the OP’s truck? It may be covered under recall; my ‘09 Tahoe was covered under GM recall last January. I ended up doing it all by myself as my dealer had a two week backlog and Amazon delivered the part in 20 hours. The software update is easy if you have a Windows 7/10 laptop, Tripp Lite USB to Serial dongle, and a Tech 2 (clones work too).


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[Gtm]

Is there a code with reduced engine power?

[03chevyhd]

12 hours ago, Gtm said:

Is there a code with reduced engine power?

I haven't pulled codes yet but it'll probably be same as others not sure. At the moment it just happened and want to know the locations of the grounds. 

[03chevyhd]

13 hours ago, tigers2007 said:

This part is in stock at your local big box auto parts store and also your local dealer. What year is the OP’s truck? It may be covered under recall; my ‘09 Tahoe was covered under GM recall last January. I ended up doing it all by myself as my dealer had a two week backlog and Amazon delivered the part in 20 hours. The software update is easy if you have a Windows 7/10 laptop, Tripp Lite USB to Serial dongle, and a Tech 2 (clones work too).


Sent from my iPhone using Tapatalk

What part is it your referring to?