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John
John, GM FACTORY CERTIFIED TECHNICIAN
Category: Pontiac
Satisfied Customers: 9176
Experience:  ASE A1-A8 w/L1 GM master technician.Factory certified/40 years experience
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Pontiac G6 GT 2005 Pontiac G6 loses power, service engine

Customer Question

2005 Pontiac G6 loses power, service engine and check engine light come on. Message on Radio reads Engine Power Reduced. Car loses power and slows till it dies. Codes that come up are P0443, P0455 and U0107 and P2135. I remove Gas cap and put back on and the problem temporarily goes away. If I stuff a rag instead of put on the gas cap it doesn't happen. Garage replaced a relay sensor but I think it's more than that. Any thoughts?
Submitted: 2 years ago.
Category: Pontiac
Expert:  John replied 2 years ago.

Hello & Welcome to JA,

Ok, the first 2 codes are evap codes & will not cause a driveability problem. Th e second 2 are the problem -DTC U0107 Lost Communication With Throttle Actuator Control Module These 2 faults are closely connected. To find this problem one will need to view the tps ,possibly when this event happens. The repair is usually replacing the throttle body., if all other data is good.

P2135 - loss of throttle actuator control data

The throttle body assembly contains the following components:

The throttle blade
The throttle actuator motor
The throttle position (TP) sensor 1 and TP sensor 2
The throttle actuator control (TAC) module
John, GM FACTORY CERTIFIED TECHNICIAN
Category: Pontiac
Satisfied Customers: 9176
Experience: ASE A1-A8 w/L1 GM master technician.Factory certified/40 years experience
John and other Pontiac Specialists are ready to help you
Customer: replied 2 years ago.
Why does removing the gas cap and/or replacing the gas cap with a rag stop the problem from happening. From what I understand that would suggest an EVAP issue?
Customer: replied 2 years ago.
Relist: Incomplete answer.
I just would like an answer to my follow up question that why does stuffing a rag in place of the gas cap stop my problem. John was prompt and gave a good answer. I was just hoping for some follow up.
Expert:  John replied 2 years ago.
to much to try & understand ,huh. I will opt out since you allready have.
Customer: replied 2 years ago.
Just wanted follow up. No need to insult. Thank you for your help. Just curious why the rag stops the problem.
Expert:  Mike S. replied 2 years ago.

2005 Pontiac G6 6 Cylinders 8 3.5L SFI.

To answer your question about why stuffing a rag in the gas tank causes the problem to go away, I can only say.

The 2 codes P0443 and P0455 refered to the Evaporative Emission (EVAP) Purge Solenoid Control Circuit and Evaporative Emission (EVAP) System Large Leak Diagnostic. Perhaps the original cap is bad, have you tried a new gas cap.
The EVAP is a closed system and without the cap or a faulty or leaking cap, the system would loose pressure or vacuum. Plus, when you stuffed a rag in there you must have been making a good enough seal.

Customer: replied 2 years ago.
I did replace the cap and it was fine for a week or two. I worked good until I drove off with the cap on my trunk. I did go back and get the cap but since then it started acting up again. Could I have damaged the cap to the point where I need to buy another new one?

Would loosing pressure in the evap system cause the throttle to not function properly. I guess what I'm getting at is the cap and the lack of a good enough seal in the fuel system the beginning of the problem or is the beginning of the problem the throttle body as John would suggest.

Thank you so much for your help!
Expert:  Mike S. replied 2 years ago.

After you forgot to put the gas cap on did you ever clear the code? Did the cap ever fall and hit the ground? As far as the engine loosing power, you may have more problems then a code will show. I would start off with replacing the fuel filter, clearing codes and checking the fuel pump pressure.

I wasn't even looking at those other codes cause it was already answered. I was only trying to answer the one question that you asked after relisting. If you want I'll look into it.

Customer: replied 2 years ago.
The codes weren't cleared until the garage replaces the relay the drives those codes last monday.

The cap did fall and hit the ground so I am wondering if I cause damage. I can't believe a gas cap would cause this though. My big thing about all the codes is if one could be causing the other. The origination of the problem seems to be with the fuel system and the pressure that the cap does or doesn't hold. This is all good information..thank you.
Expert:  Mike S. replied 2 years ago.
What codes have come back since clearing them? How is the engine running now?
Customer: replied 2 years ago.
Don't know yet. The engine died again today after having the relays replaced on Monday. The service engine and check engine light come on and a message appears across the radio's message board "Engine Power Reduced". The car fails to accelerate and eventually dies. I pulled to the side of the road, took off the gas cap and retightened it. I drove about 1 mile and it happened again. At that point I went back to using the rag instead of the gas cap and then drove 40 miles on the highway to work. I know, it's bizarre.... I won't be able to have the codes checked again until Monday when I take it in (that's the soonest I could get in). I'm not a do it yourselfer unfortunately.
Expert:  Mike S. replied 2 years ago.
My manual's website is down right now.
Expert:  Mike S. replied 2 years ago.

Ok, its back up. I see the "Reduced Engine Power" found under the code P2135 and U0107. Reduced Engine Power: The scan tool displays Active or Inactive. The scan tool displays Active when the PCM receives a signal from the TAC module that a throttle actuator control system fault is occurring. The PCM limits the engine power.

For more info, click here. For P2135, Possible Causes:
The throttle position indicated by TP sensor 1 disagrees with the throttle position indicated by TP sensor 2 by more than 6 percent. OR The PCM learned minimum throttle position of TP sensor 1 disagrees with the learned minimum throttle position of TP sensor 2. OR The PCM detects that the TP sensor 1 signal circuit is shorted to the TP sensor 2 signal circuit.

For U0107, Possible Causes:
Invalid or missing serial data messages are detected for a predetermined period of time.
OR
The throttle limit is exceeded while operating in the Reduced Engine Power mode.

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