Impala Forums banner

Reduced Engine Power P2138 and P2127

23K views 24 replies 11 participants last post by  colinabba 
#1 ·
Hey Guys I have 2012 Impala LTZ 3.6L. I need some help with this. I have had an ongoing problem for almost a year with the p2138 code Pedal position sensor. I replaced it and it was fine for a while then did it again. I took to dealer and they could not diagnose it and check all plugs so I got it back and I replaced pedal again and then it gave P2127 throttle body sensor. I replaced the throttle body and it was for a few days and getting codes again. I reset the check engine light and was fine again. I put a K&N intake on it and it was back doing it again showing both codes. I have checked every plug from dash to harness under the hood even wires to ECU. I finally decided to take to another chevy dealer because it went into reduced engine power with same codes about 10 times that day but before I did I removed the cold air intake so they wouldn't try to blame it on that. They have had the car for a week and cannot get it to go into reduced engine power but they have seen the codes in the system. they said they are going to check wires to ECU. they have agreed with me that it could be an intermittent problem and could be ECU. Has anyone else had this problem. Its getting frustrating. Thanks in advance. Robert
 
#3 ·
I put a K&N intake on it and it was back doing it again showing both codes. <snip>

it went into reduced engine power with same codes about 10 times that day <snip>

I removed the cold air intake so they wouldn't try to blame it on that. <snip>

They have had the car for a week and cannot get it to go into reduced engine power <snip>
Reading your summary, I cannot help but think there's a connection between the K&N and the codes. It's not at all clear why, tho.

The only thought I have is the ECU. Is it still located in the cold air intake box on a 2012? Could the ECU be not getting enough cooling airflow when the K&N is installed instead of the stock setup?

I think it's a long shot, but that's the only connection I can make.

Doug

.
 
#4 ·
Reading your summary, I cannot help but think there's a connection between the K&N and the codes. It's not at all clear why, tho.

The only thought I have is the ECU. Is it still located in the cold air intake box on a 2012? Could the ECU be not getting enough cooling airflow when the K&N is installed instead of the stock setup?

I think it's a long shot, but that's the only connection I can make.

Doug

.

I'd agree with you if it weren't for the vehicle throwing codes between replacing other parts and putting on the K&N. Additionally, enough people have put on those CAI I think this issue would've turned up for more than just one by now if it were a major factor. Seems like he has an intermittent issue (which are by far the most fun to diagnose). Best guess is it could just be some electrical connection being shady.


I'd inspect all the electrical connections (wire to connector, connector to connector, etc) for good contact, corrosion, and wear. Could be something as simple as a wire in a connector being a hair loose. PITA to find though... Hopefully the dealership will do this as part of their inspection.
 
#5 ·
The computer is still under the airbox but with the cold air intake installed there is more air to it so it shouldn't be getting hot. I have checked every connection from under the dash to the engine compartment and the ones that are on the strut towers. I have even wiggled the wires while the car was running to see if it would set a code and it does nothing not even when I rev the engine. It will only said if the car is driving and the engine is under a load. I too think it's an ECU problem. My nephew went yesterday to the dealer and drove it with them to see if we could get it to do it at work and going to reduced power so they think it's intermittent at the ECU also. They are going to look at the wires to the ECU today. I did notice since the cold air intake and filter has been sitting in the garage has been leaking a lot of oil from the filter and when I had put the stock airbox back on I noticed the master flow sensor had oil on it so I cleaned it. I'm thinking that the filter had too much Oil on it and could be causing the problem. I had ordered another cold air intake for my other car and I put it on and there is not that much oil at all on the filter so I'm thinking maybe they overdid it on that one But I will keep you guys updated on what happens. When I get the car back I'm going to put the cold air intake back on it and if it goes into reduced engine power again and then I'm just gonna take it off and leave it off. I appreciate all your feedback. Thanks
 
#6 ·
I did notice since the cold air intake and filter has been sitting in the garage has been leaking a lot of oil from the filter and when I had put the stock airbox back on I noticed the master flow sensor had oil on it so I cleaned it. I'm thinking that the filter had too much Oil on it and could be causing the problem. I had ordered another cold air intake for my other car and I put it on and there is not that much oil at all on the filter so I'm thinking maybe they overdid it on that one But I will keep you guys updated on what happens. When I get the car back I'm going to put the cold air intake back on it and if it goes into reduced engine power again and then I'm just gonna take it off and leave it off. I appreciate all your feedback. Thanks
They have recharge kits for these filters which would allow you to clean the filter then re-oil it. That'd probably be a good idea before just calling it quits with the filter. On a side note, if you do decide to leave it off, I've been looking for a good deal on one of those lol
 
#8 ·
Well after the dealer having the car a week and two days we got it back today and its driving ok so far. They could not duplicate the problem so there was no charge. they said they checked every connector and wire for the ECU and pedal sensor and Throttle body sensor. They also checked the ECU wiring. They did somehow crack the clear plastic bezel that covers the speedometer and gauges but they say they didn't do it. They will have to check with manager on what they are going to do about it, was not very happy about it.
 
#10 ·
Thanks for the reply Doug. I did mean maf sensor. It was autocorrected. I called K&N and they are sending me a cleaning kit for the filter. They think someone might of had it before and returned it and over oiled it. I also talked to a tech guy about another part that looked warp and I sent them pics and they are reviewing and may send me new parts. I did order a new MAF sensor just Incase before I had taken it to dealer so I have an extra one. I'm waiting for them to see what they are going to do and if they are sending new parts. Hopefully it will be ok.
 
#13 ·
I get it, that's what I meant.

I searched youtube for intermittent pedal and tb codes for a couple hours one day, and there's been a lot of people with nightmare problems.

I've seen voltage wires breaking contact, bad grounds, and you just have to play with the wire bundle and check and check and check voltages and grounds to find the issue.

Not many service techs have the patience.

One guy even took apart a tb and found the contacts that wipe across the carbon switch can separate giving varying voltage feedbacks to the ECM.
 
#14 ·
Earlier this month I had P2127 on my 2008 LS that put the car in reduced power. Since it was immediately after a heavy rain, I disconnected the pedal position sensor connector, applied electrical grease, and reconnected. Cleared the code and started driving. It's been about 3 weeks and no issue yet. If the code returns, I plan to grease the big connector under the hood and go from there.
 
#17 ·
Thanks.
Okay so I also was looking in the factory manual for my 2007 and for that year it was saying that the tech should check the wheel speed sensor for voltage with ignition on OFF position. Says check voltage to sensor and it should be 850-1350 and spin the wheel to see it change and also wiggle the wires while checking for bad connection. if not in range change the sensor. ill see if i can find a link for it and post it.
 
#18 ·
#20 ·
I have a 2008 Impala LS 140K miles on it. I have been getting the same "Engine Power is Reduced" message for about the past 6-8 months. Back in November of 2017 when it first happened, I searched online and found a lot of videos about the throttle body and the TPS sensor. I changed out the sensor. Didn't solve my issue, then I replaced my pedal since I was getting the P2127 and P2138. This appeared to be the answer as the check engine light went off immediately and my problem was solved for about 3 weeks. Then driving one day as I hit the gas pedal to accelerate it went right back into "Engine Power is Reduced" mode. VERY FRUSTRATING!!

Fast forward to May, 2018 I take the car to my mechanic while I was out of town for the weekend and he looks at it and calls me and tells me I need my pedal replaced because of the codes he was getting. I told him I already replaced my pedal about 4 months prior and he says, "Oh, well let me see if I can calibrate and reset it...maybe that's all you need." He calls me back the next day and he says he's unable to get it and that i will have to take it into a dealership so they can do something with the computer or flash ECM (I can't remember exactly what he said). Anyway, I pick up my car that Monday and although my mechanic hadn't solved my issue, it did appear that my car wasn't going into "Engine Power is Reduced" mode as often. Maybe 1 time every 3-4 days. Sometimes I could go a whole week without the issue.

This issue only appears to happen when I'm hitting the gas pedal. To combat this, what I'll do it when I get up to speed I will go into cruise control and use the +/- to change speeds and such. Typically this allows me to stay out of Engine Power Reduced mode. However at time I have to stop and slow down, then when I hit the pedal again, boom, it goes back into that mode. Needless to say, It's very frustrating because outside of being in this stupid mode, my car runs beautifully. That is why I know it's not an "engine" problem, but it has to be a computer or electrical problem somewhere.

I'm concerned about taking the car to the dealer because I feel like they're just going to say, "you need a new pedal" and then they'll charge me an arm and a leg for it. Then I'll get the car back and three weeks later I'll get that error message again. Has anybody found the sure fire solution to this problem? I'm planning on getting a new car come November anyway, but I'm willing to put a few bucks into this one to fix it so I can sell it before I get my new car.

Thanks!
 
#21 ·
Man, it sure does sound like the gas pedal is the issue (especially since I've heard of this exact issue before and it *was* the pedal). I know that you replaced it 4 months ago, but I wonder if either it was a cheap/bad part or mabe there is wiring that goes to the pedal that is shorting out and causing the sensor in the pedal to fry - or something along those lines.

Being that the new pedal solved the issue for so long, you'd think that it's related somehow... Not sure what a new pedal costs, but it if they are cheap, it might be worth a shot to replace it again before bowing down to a dealership... The cost of the pedal is probably less than 1 hour of "troubleshooting" time at a dealership...

Wish I had a better answer for you....
 
#22 ·
Yea, I think I will go ahead and try another pedal before I give in to the dealership. Very frustrating. I'm going out of the country on business for a week and I was hoping maybe the dealer would look at it and be able to fix it with something simple. Very optimistic thinking, I know!

Question, is there some kind of learning or calibrating I have to do after I install a new pedal? I thought I was reading that these cars are supposed to relearn themselves by just driving around. Clearly my car didn't do that last time and maybe that is where the disconnect is.

Any further thought on that?

Thanks!
 
#23 ·
I'm not aware of any kind of "pedal relearn", but if you want to have the computer relearn everything from scratch, you can disconnect your battery overnight (not sure exactly now long it needs to be disconnected, but overnight will do it for sure). Then the computer will relearn everything from scratch. I'd probably try that even before replacing the pedal, just in case...
 
#24 ·
Accelerator Pedal Sensor Connector



I've now switched out my pedal and left the battery disconnected for an hour and after driving the vehicle for about 20 minutes around town, my check engine light returned and the engine power reduced message came back.

After reading some more in depth this past weekend online, I'm convinced it has to be something between the connector of my pedal sensor and my computer. If I were to change out my connector, where can I find instructions on how to do so? Is it something I have to disconnect in two places and just reconnect or do I need to cut the wires and connect the new ones? Any help would be appreciated.

Thanks
 
#25 ·
p2138 with new APP

I too am having a similar issue right now in my 08, but it seems like the frequency is a lot less, and I am now getting code p2138 (had 2123 once before). I'm currently trying to see if there is a correlation to the rain, as I replaced the APP sensor with a dorman equivelant a few weeks back when I first had code p2138, and my engine has been reducing again, but I've only noticed it after a code clear twice when it was raining. I know it isn't the throttle body, as I replaced that whole part and sensor last July, and had no problems again until about a month ago. I plan to check the connections Sunday and spray them down with dielectric grease (including ECM connectors). I'm hoping this fixes the problem, as I'd expect the ECM would be throwing off more codes than pedal specific ones if it was having a computer issue. I will keep you updated if I find anything screwy near the ECM connections.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top