Reduced engine power warning & traction control off

This has happened to me twice now, 2 weeks between occurrences:

Driving to work, about 10 minutes into the trip - traction control light comes on, "Reduced engine power" message appears on DIC, and check engine light comes on.

The car is an '08 Prix, no charger, with 51K on it. This is actually the first trouble I've had with the car since it left the dealer lot.

I pull over, turn car off. Turn back on - traction light goes out, and engine is running at full power. The check engine light remains on for about 5 starts/stops then goes away.

I haven't had the engine scanned yet. The only thread here I could find was someone who had a similar issue, and a GM bulletin was posted by someone, which recommended replacing the throttle body. The person decided to clean the throttle body, and that was the last post.

I was thinking of removing the individual electronic components from the TB and cleaning them and the area around them in the TB. (I have the sensor-safe cleaner for TB's).

I don't think this error condition would be a warranty issue, but I'm not sure. It's a MAJOR hassle for me to get the car to the dealer.

If anyone has any suggestions, I'd be glad to hear them.

I suggest you bring it back to the dealer and let them figure it out, it must still have warranty????

I found this bulliten, this may be the problem, but I would still bring it in to the dealer to let them fix it


The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
<A href="http://gsi.xw.gm.com/si/showDoc.do?docSyskey=2230459&from=sm#ss1-2230459">Condition/Concern:

Some customers may comment that the Service Engine Soon light is illuminated. In addition some may also comment that the vehicle was exhibiting a hesitation and/or had the "reduced power mode" symbol or message displayed. When checking for diagnostic Trouble Codes (DTC) in the Powertrain Control Module (PCM), codes P1125, P2120, P2125 or P2138 may be found.
<A href="http://gsi.xw.gm.com/si/showDoc.do?docSyskey=2230459&from=sm#ss2-2230459">Recommendation/Instructions:

1. Remove the engine cover

http://gsi.xw.gm.com/image_en_us/gif/000/002/177/2177259.gif
http://gsi.xw.gm.com/si/images/tif.gif (http://gsi.xw.gm.com/si/showTif.do?image=2177259)

2. Inspect the underside of the wiring harness for evidence of chafing on the intake manifold.

http://gsi.xw.gm.com/image_en_us/gif/000/002/177/2177261.gif
http://gsi.xw.gm.com/si/images/tif.gif (http://gsi.xw.gm.com/si/showTif.do?image=2177261)

3. If chafing is found on the conduit, then open the wiring harness and inspect the wires for damage.

http://gsi.xw.gm.com/image_en_us/gif/000/002/177/2177262.gif
http://gsi.xw.gm.com/si/images/tif.gif (http://gsi.xw.gm.com/si/showTif.do?image=2177262)

4. Inspect all the wires in the area where the chafing occurred and repair as necessary. Pay close attention to the black wire (Circuit 1161).
5. Place the wires back inside the conduit and reposition the conduit on the engine so that wiring conduit no longer rubs against the manifold when the engine cover is installed.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Another thread here that I wanted to follow up on. The Engine Power Reduced message happened 2-3 times, then went away. A year and a half later it came back with a vengeance, happening 10-15 times over a 3 week period. I took the car to a dealer, they found a code indicating a problem with the throttle. Incidentally, this car has an all electronic throttle system, no more cable from the accellerator pedal. Unlike my son's '04 GP, it doesn't have the usual MAF sensor, TPS sensor, etc, as separate modules.

Ao anyhow, the dealer spent a day on it, called GM and talked about it, and they all concluded the COMPUTER was the problem. The warranty on the comp is 80K. I was at 80,500K. Ha ha. They covered it anyway, otherwise I'd have been out about $700-800.

I've had the car back for 6 days, and no problems yet. I will feel better if I go a solid month without a repeat.

Most every reduced power scenario I've seen is related to the electronic throttle body or the wiring to it.

Most every reduced power scenario I've seen is related to the electronic throttle body or the wiring to it.

That's exactly what I expected it would be Rich. The computer didn't make much sense to me. I can only assume since GM had to pay for it, that they ruled out the less expensive parts first.

Just out of curiousity, do you know what a throttle body costs, new or used? I won't be surprised if the problem reoccurs.

Watch for rain, or car wash water rolling onto a drive-by-wire system, water will short the throttle body control module, and throw car into reduced power mode.

See Jaguar www.automotiveforums.com/vbulletin/showthread.php?t=975140 (http://www.automotiveforums.com/vbulletin/showthread.php?t=975140)
,or Yukon www.automotiveforums.com/vbulletin/showthread.php?t=974347 (http://www.automotiveforums.com/vbulletin/showthread.php?t=974347)

Toyota Recall is having problems with there Drive-by-wire system.

Most every reduced power scenario I've seen is related to the electronic throttle body or the wiring to it.

My car went into reduced power mode again this morning, even with the new computer. It's back to the drawing board. With 81.5K on it, I'm pretty sure the warranty's all up. Ouch.

Have you had any ABS or Traction Control system issues otherwise? Any hubs/wheel sensor ever replaced?

The ABS and traction control systems will reduce engine power if there is an issue or malfunction whether detected or not. <---This is the most common and logical scenario.

Was it ever scanned both odb-ii and ABS systems?

No ABS or traction issues, and no hubs or sensors replaced. I don't know exactly what the GM dealer did, but I know they spent several hours on it and also consulted with someone at GM about it.

99% of the time, I get the reduced power issue in the first 5-10 minutes of my trip in the morning. The car is garaged at about 50 degrees. It sits outside at work all day long, yet I don't think I've ever had a reduced power issue coming home at night when the car is much colder.

Usually the reduced power happens only once per day, although it did happen 2 or 3 times one morning. Considering I drive 110 miles/day, it's pretty intermittent, happening about once every 200-400 miles.

You could have an issue with the ABS module providing the wheel sensors are OK. The ABS braking and traction control systems runs an initialization test. At engine startup and when moving after the vehicle reaches a certain speed like above 8-10 mph to test all wheel sensor inputs. Personally to start I'd check all four wheel sensors with a comparative scan using an ABS capable scan tool (GM Tech 2).

OK, I'll keep that in mind. The only other thing I can add is that when they scanned for engine codes, the code they found was related to the throttle body. Again, I don't know what led them to believe it was the computer. Maybe the fact that they couldn't reproduce the problem...IDK.

Wow! :shakehead GM copyrighted material posted. :nono:


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I found this bulliten, this may be the problem, but I would still bring it in to the dealer to let them fix it


The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
<A href="http://gsi.xw.gm.com/si/showDoc.do?docSyskey=2230459&from=sm#ss1-2230459">Condition/Concern:

Some customers may comment that the Service Engine Soon light is illuminated. In addition some may also comment that the vehicle was exhibiting a hesitation and/or had the "reduced power mode" symbol or message displayed. When checking for diagnostic Trouble Codes (DTC) in the Powertrain Control Module (PCM), codes P1125, P2120, P2125 or P2138 may be found.
<A href="http://gsi.xw.gm.com/si/showDoc.do?docSyskey=2230459&from=sm#ss2-2230459">Recommendation/Instructions:

1. Remove the engine cover

http://gsi.xw.gm.com/image_en_us/gif/000/002/177/2177259.gif
http://gsi.xw.gm.com/si/images/tif.gif (http://gsi.xw.gm.com/si/showTif.do?image=2177259)

2. Inspect the underside of the wiring harness for evidence of chafing on the intake manifold.

http://gsi.xw.gm.com/image_en_us/gif/000/002/177/2177261.gif
http://gsi.xw.gm.com/si/images/tif.gif (http://gsi.xw.gm.com/si/showTif.do?image=2177261)

3. If chafing is found on the conduit, then open the wiring harness and inspect the wires for damage.

http://gsi.xw.gm.com/image_en_us/gif/000/002/177/2177262.gif
http://gsi.xw.gm.com/si/images/tif.gif (http://gsi.xw.gm.com/si/showTif.do?image=2177262)

4. Inspect all the wires in the area where the chafing occurred and repair as necessary. Pay close attention to the black wire (Circuit 1161).
5. Place the wires back inside the conduit and reposition the conduit on the engine so that wiring conduit no longer rubs against the manifold when the engine cover is installed.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

With the traction control light on, it could be a wheel speed sensor issue, but on these GM vehicles with the electronic throttle bodies, when it goes into reduced power mode its almost always related to the PCM getting mixed signals between the accelerator pedal sensor and the throttle position sensor (which is part of the electronic throttle body). The throttle body is the highest failure part if the wiring is ok.

Yeah Rich I'm curious how all that works now versus the previous generation Grand Prix. I guess I'll have to shell out some bucks on the GM Helm Factory Service Manual. I prefer doing all my own troubleshooting and work versus the stealership whenever possible and within reason. My GM 1 year certified vehicle warranty expires on my GXP this summer. :crying:

BTW - I still only have 38.5K miles on her. :grinyes:

Well I thought I'd post back on this for an update. The car is still having the same issue with the reduced power. 99% of the time it's happening within the first 5-10 minutes of my morning commute, virtually every day.

I asked the dealership why they replaced the computer. They said because it wasn't responding properly when they connected their diag tool. They said they spent hours messing with it, called GM, and GM advised replacing it. If that was in fact needed, it was a separate issue. When I told them the car is still exhibiting the same behavior, they said they could install a new throttle body for $260 (part) and offered to eat the labor.

gmpartsonline.com sells the TB for $198. I also found one at a reputable online salvage company from a Prix that got totalled with only 4K miles. They want $130 for it, with a lifetime warranty.

So, I'm thinking about going ahead and buying the one for $130 and popping it in. I don't really have any other ideas. The behavior is very odd. Why does it fail once per day, and so close to the same time every day? Very strange.

Start with your battery, its electrical.. Just had this happen to me. Car would run only for 2 minutes then go into safe mode. Its not giving enough power to the ecu. Replace the battery first, clean the throttle body, new filter etc. Mine had 131,220 miles on it. So far so good.

Start with your battery, its electrical.. Just had this happen to me. Car would run only for 2 minutes then go into safe mode. Its not giving enough power to the ecu. Replace the battery first, clean the throttle body, new filter etc. Mine had 131,220 miles on it. So far so good.

Necropost much? :grinno:

It was the throttle body... 5 yrs & 105,000 miles ago. Still running strong.

Hello,
I have ran into this issue where my Grand Prix 08 went in engine running on reduced power, from regular driving. So far Ive had the throttle body changed twice, the accelerator, the computer and the issue is engine is still running on reduced power HELP!!!!! btw I did have my hub barron replaced.

More often than not, it is not the throttle body.....the problem usually is the wire harness to it....could be a bad connector in the harness onnector or a broken wire in the the harness(insulation intact, but wire could be broken inside it)....