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Discussion Starter #1
The reduced engine power sensor on my 2003 Trailblazer keeps activating.
I have had it in the shop 5 times. Dealer has installed software updates, but
problem persists and is getting worse. They have no idea what is causing
this. Factory support has been no help. Looking for solutions.
 

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2007 chevy trailblazer_ls
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Welcome to the group. Something that you could do to help us diagnose your problem is to fill in your profile. Once you do that, the info will start flying.
 

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Welcome to the site.

The "reduced engine power" message is not a sensor. It is a message from the PCM that some sensor(s) or operating parameters are not reporting correct information to the PCM or the sensor(s) are providing information that is causing the PCM to protect the powertrain. The problems that can cause a reduced engine power are probably too numerous to list.

Next time it happens, make sure you get the DTC codes and post them to the site. You should get many responses once you have some codes that everyone can make sense of. There are several very helpful members that can start to diagnose the problem with a little additional information.

I also agree with rcam81, fill out your profile so we all know what configuration you are driving.
 

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2002 chevy trailblazer_ls
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A friend of mine had his accelerator pedal sender-resistor gizmo fail and got the reduced power light. Replaced the pedal ass'y and that fixed it. I think it set a code so you might get that checked somewhere like AutoZone who will do it free. A stored code should lead you in the right direction.
 

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My wife had this happen on the 06 5.3L and it turned out to be the throttle body and the ignition switch:confused:. Truck wouldn't go over 30MPH and the reduced engine power light was on. It definitely didnt protect the motor because right now it's in for a new long block.:worried:
 

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2006 chevy trailblazer_ls
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My wife had this happen on the 06 5.3L and it turned out to be the throttle body and the ignition switch:confused:. Truck wouldn't go over 30MPH and the reduced engine power light was on. It definitely didnt protect the motor because right now it's in for a new long block.:worried:

Apples and Oranges...
 

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Be it the pedal or the throttle body, it is about the same. The sender or the receiver, the signal did not reach it's destination. But, I do know the computer does not shut down engine power due to signal input. It only tells you the drivetrain is not functioning properly. +/- 7-10% expectancy.

How much money would GM make if they shut down an engine due to heat or oil pressure, or had the DIC tell you exactly which sensor or part went bad?:undecided
 

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Reduced Power, engine light on

Just bought 2005 GM Buy Back loaded EXT with 25k on it. Immediately after brake controller was installed under dash, the reduced power thing happened with a check engine light on. Dealer found wiring harness under dash problem and fixed it.
 

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2003 chevy trailblazer_ltz
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Reduced Engine Power

I am looking for some assistance. My 2003 Trailblazer has 63,000 miles and has been experiencing the reduced engine power problem. A GM dealer has replaced a fuel sensor, entire wiring harness, computer, and it still is occurring. The only other thing they plan to try is the accelerator assembly.

Any thoughts on whether or not this should fix the problem??? I've been a very loyal GM owner, but this experience has me reconsidering that...
 

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2004 gmc
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On whose dime are they doing that INSANE and EXCESSIVE amount of guessing? :eek:

What exact code shows up in the computer when it goes into REP mode and sets the SES light?

Typically the code will point to the throttle body or the accelerator pedal. There's a TSB that it might also be chafing in the wiring harness from the PCM to the fan clutch, or a failure in the fan clutch. We're very familiar with it here on trailvoy - hard to believe the dealer isn't.
 

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Like roadie said you really need to find out what the codes are setting the REP light.

I had this problem once and I ended up replacing the throttle body which was the most expensive thing i have had to do to my truck, but no more REP light.
 

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Still having problem...

I have shelled out $1,200 for the fuel sensor, accelerator assembly, and wiring harness. The computer was covered under a warranty of some type. After the 4th trip where they replaced the accelerator assembly...it has been fine for the last 2 weeks...until today. Same problem....I won't pay Reeder Chevrolet another dime to fix this...taking it back tomorrow...any suggestions???:mad:
 

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2004 gmc
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We gave you suggestions on 3/20 and you didn't respond. I'm betting on it being the fan clutch or the harness. Have those goofs EVEN READ the TSB?

What is the code?
 

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Sorry for the delayed response...I'll ask tomorrow what the code is....they actually replaced the fan clutch almost 2 years ago...hard to believe this is a licensed GM dealer...
 

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Ggggrgrrr

On whose dime are they doing that INSANE and EXCESSIVE amount of guessing? :eek:

What exact code shows up in the computer when it goes into REP mode and sets the SES light?

Typically the code will point to the throttle body or the accelerator pedal. There's a TSB that it might also be chafing in the wiring harness from the PCM to the fan clutch, or a failure in the fan clutch. We're very familiar with it here on trailvoy - hard to believe the dealer isn't.
I am having the same issue. Local mechanic said the code was the accelerator pedal. Put 2 aftermarket ones on and worked ok for about 3 weeks each time. Now the dealer says that they could put on a $380 GM pedal but no guarantee that it will fix the problem. (big surprise). Buy the way, the fan clutch sounds like a Tomcat ready for launch and that is another$800. Are these problems related? Seemed the Reduced Engine Power atrted back when I noticed the fan clutch starting to go out.
 

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...Are these problems related? ...
Yes. I'd predict 90% chance it's in the fan clutch or its wiring harness. Just pull its connector off and see if the REP light goes out. You might get a SES light with a fan clutch code, but it's a good experiment to do. Fan clutches can cost less than $200 if you're doing it yourself. There have been reports of erratic aftermarket APP sensors that GM parts can fix. Intelligent use of a high-end scan tool can distinguish this sort of problem from a bad fan clutch. Tell the mechanic that the fan clutch, APP, and Throttle Position Sensors all share the SAME 5V reference circuit. But they have access to schematics and TSBs that say the same thing.
 

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2005 gmc envoy_denali_xl
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REP - will not start

First let me say thank you to all who have posted here. I'd been in lurk mode since before I even registered as a member, and never needed to post a question on account of the wealthy search.

My problem with the REP started a month ago on a hot afternoon after (coincidentally?) the truck had earlier run out of gas. GM service replaced the ignition switch. Next afternoon it got hot, driving in traffic, engine quits again. Then my old mechanic digs through the TSB's on it to trace it to some voltage problem, and thinking the sensor in the throttle is sending some faulty data back to the PCM, recommends replacing that. I put in a new throttle body myself yesterday.

After an hour of driving this morning, it quits again. What I have found gets me back on the road when stranded is to disconnect the battery cables, leave the hood up, and after it cools off 20-30 minutes its starts and runs fine.

So when I get it back home I find this thread on the fan clutch connector. So I disconnect that (5-wire @ top-right of radiator shroud?). It won't start. Cranks strong, no spark. Plug it back in, still no start. I got the codes (P0689; P2101; P0442; P1682). I left it sit there, an hour later came back, now it starts. With it running, same 4 codes + P1516 added.

Pulled off the connector again, no change. Other possibilities he had also suggested was bad battery cable, loose ground under fuse box... any other ideas? Way out of warranty, and the service guy @ GMC seemed to want to jump down the rabbit hole on my dime.

Scott
 

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2005 gmc envoy_denali_xl
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REP - won't start

Sorry... P0443. Typo.
If it were a bad cable or fuse box connection, why would it only do it when it's hot?

srb
 

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REP when hot

Judging by the "views", is this the second most common OEM concern?
Here's an update. Truck starts when cool. Disconnected fan clutch conn... still quits once it got too hot. In extreme temps (100+ weather) it may take a few hours before it will start again. As long as outside temp is <85 and I keep moving, it will run fine for hours until I hit traffic. Sometimes it will even make it to my destination if hot, but refuse to start again once it's turned off.

Plugged or unplugged, fan clutch seems to have no impact. It appears to only quit when I lift off the accelerator, like preparing for a turn or stop @ an intersection. I don't think it's ever done it with my foot on the gas. So it would seem to be a faulty voltage reading.

Anything besides battery/ground cable/fuse block I can look at diagnosing Monday when I can bring it in to somebody with the right tools? (see previous post for codes)

Replaced ignition switch and throttle body. Have NOT replaced APP or crankshaft sensor. Still original alternator/voltage reg.

It would seem to be something that only reacts to heat in the engine compartment. Similar to "TB shuts off when it gets hot" < http://forums.trailvoy.com/showthread.php?t=88932 > except it keeps going if cool enough outside.

The Roadie suggested having a scan tool connected when it dies. Easy enough to predict, if I can get somebody to go along with it. I'm just afraid of the dealer service dept insisting I jump down the rabbit hole to find it. I don't mind the process of elimination if the parts are cheap & I can do it myself. BTW - there's an ad post < http://classifieds.trailvoy.com/showproduct.php?product=4869&cat=2
> for a good throttle body if anybody else out there _actually_ needs one. :duh:

Thank you. I'm really sucking wind on this one...
Scott
 

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2005 gmc envoy_denali_xl
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Solved

Turned out to be the fuse box (electrical panel) under the hood. Crack &/or shorted wire inside. $463 for replacement, $810 total for the day-an-a-half visit.

srb
 
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