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Ask GM Tech (Cam) Your Own Question

GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 27664
Experience:  GM Grand Master Technician 2007. 11 years experience.
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Reduced engine power message, DTC codes..engine shut down

Resolved Question:

getting reduced engine power message, DTC codes are P1516 P2101 and P2176. car had been somewhat hesitant prior to engine shut down.
Submitted: 3 years ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 3 years ago.

GM Tech (Cam) :

Hello, I'm Cam. Please include all the details about your issue so I can accurately advise you. I cannot see your vehicle so please be detailed.

GM Tech (Cam) :
#PIP4578A: SES Light Idle Surge And/Or Reduced Engine Power Mode With DTCs P0068 P0121 P0506 P0507 P1516 P2101 P2119 And/Or P2176 - Clean Throttle Body And Perform Idle Learn Reset - (Feb 9, 2010)


 











Subject:SES Light, Idle Surge, and/or Reduced Engine Power Mode with DTCs P0068, P0121, P0506, P0507, P1516, P2101, P2119, and/or P2176 - Clean Throttle Body and Perform Idle Learn Reset


 










Models:2007 Buick Rainier











2007-2009 Cadillac CTS-V, Escalade











2008-2009 Chevrolet Colorado











2006-2009 Chevrolet Avalanche, Corvette, Express, Impala, Monte Carlo, Silverado, Suburban, Tahoe, Trail Blazer











2008-2009 GMC Canyon











2006-2009 GMC Envoy, Savana, Sierra, Yukon











2007-2008 Hummer H2











2008-2009 Hummer H3











2007-2008 Pontiac Grand Prix











2008-2009 Pontiac G8











2006-2009 Saab 97x











With a V8 Engine






This PI was superseded to update model years and add information concerning idle surge, reduced engine power mode, and/or DTCs P0068, P0121, P1516, P2101, P2119, and/or P2176 that may be experienced on high mileage vehicles. Please discard PIP4578.




The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.



Condition/Concern:



As carbon builds up in the throttle body of a high mileage vehicle, the ECM/PCM learns to compensate by increasing the throttle plate angle.


If enough carbon builds up, an idle surge, deceleration surge, tip-in hesitation, reduced engine power mode, and/or DTCs P0068, P0121, P1516, P2101, P2119, and/or P2176 may be experienced on high mileage vehicles.


If the throttle body is cleaned without performing an "idle learn reset/reset idle learn" with the Tech 2, the ECM/PCM may continue to compensate for previous carbon build up, causing it to return with a similar concern as well as DTCs P0121, P0506, and/or P0507.


In a similar fashion, if the ECM/PCM of a high mileage vehicle is replaced and/or reprogrammed without performing the Throttle/Idle Learn outlined in SI, the ECM/PCM may no longer compensate for existing carbon build up in the throttle body, causing it to return with a similar concern as well as DTCs P0121, P0506, and/or P0507.



Recommendation/Instructions:



If SI diagnosis does not isolate the cause of this concern, inspect the throttle body bore and plate for obvious carbon build up.


If carbon is present, follow the Throttle Body Cleaning Procedure in SI to clean the throttle body.


After ensuring that the throttle body bore and plate are clean, perform an "idle learn reset/reset idle learn" with the Tech 2 and re-evaluate the concern.



Customer:

reading your info.... the car was hesitant on accel prior to engine shut down. it also had a idle surge then shut down all today. I changed plugs last week, all connections were checked and OK.

Customer:

approx 13700 miles on vehicle

GM Tech (Cam) :

Ok, I would still try the cleaning as a start. Can you do this now and reply back?

Customer:

clean how, solvents, or disassemble?

GM Tech (Cam) :

Carb cleaner and a rag are best. Don't try to takeit apart.

Customer:

great... you will be avail for reply later... if thisis problem, i need to know how to reset, or will I need a scan tool? i am going to parts store now....

GM Tech (Cam) :

Take the battery cables off the battery, hold the ends together for 10 seconds then attach them to the battery and see what happens. This will reset the whole vehicle.

Customer:

I will clean and get back to you

GM Tech (Cam) :

Bookmark this page so you can easily navigate back to it, and so you know, you can reply at any time for follow up information regarding this issue, even after you accept my answer and I will reply.

Customer:

clarify... clean, reset, check, then reply back to you?

GM Tech (Cam) :

sure,.

Customer:

ok

GM Tech (Cam) :

.

Customer:

ok.... cleaned throttle body and MAF, cleared codes, started fine, drove ok, i thought it had a little pull at stop idle in drive, got to gas station (about 5 mins), chimes and engine power down and engine light on again......

GM Tech (Cam) :

OK, then we are likely down to the throttle body then.

Customer:

great.......

Customer:

what now?

GM Tech (Cam) :

WEll, if we had the code I could confirm for you. Did they tell you the code?

Customer:

i dont know what code it is this time, I came back home assuming they were the same

Customer:

so i need the codes again?

GM Tech (Cam) :

Yes, but if you had work done at a shop, then it should be on your work order.

Customer:

no shop, got codes at auto zone

GM Tech (Cam) :

Ok, is there a way to get them again?

Customer:

i guess i have to go back there and get them I dont have a scan tool

Customer:

going to get them will check back when i return

GM Tech (Cam) :

OK, sorry to make you go out again, but to be accurate we need those.

Customer:

same codes 1516, 2101 2176

Customer:

it surges when you put it in drive, then engine powers down

GM Tech (Cam) :

  1. Inspect the throttle body for the following conditions:








    A throttle blade that is NOT in the rest position










    A throttle blade that is binding open or closed










    A throttle blade that is free to move open or closed WITHOUT spring pressure



  2. With the ignition ON, and the throttle body disconnected, measure for voltage between the TAC motor control 1 and 2 circuits and a good ground. The voltage should be 0 volts.








    If voltage is more than 0 volts, test the affected motor control circuit for a short to voltage or a faulty ECM.



  3. With the ignition ON, and the throttle body disconnected, probe the TAC motor control 1 and 2 circuits with a test lamp connected to B+. The test lamp should not illuminate.








    If test lamp illuminates, test the affected motor control circuit for a short to ground.



  4. Ignition OFF, allow sufficient time for the ECM to completely power down.

  5. Connect a DMM between the TAC motor control 1 circuit and ground.

  6. Using the 1 ms Peak Min/Max feature set to the 40 V scale, measure the voltage while turning ON the ignition. The max voltage should be within 0.5 volt of B+.








    If the voltage is not within 0.5 volt of B+, test the TAC motor control 1 circuit for an open, high resistance, or for a faulty ECM.



  7. Turn OFF the ignition.

  8. Connect a DMM between the TAC motor control 2 circuit and ground.

  9. Using the 1 ms Peak Min/Max feature set to the 40 V scale, measure the voltage while turning ON the ignition. The max voltage should be within 0.5 volt of B+.








    If the voltage is not within 0.5 volt of B+, test the TAC motor control 2 circuit for an open, high resistance, or for a faulty ECM.



  10. If all circuits test normal, replace the throttle body.

Customer:

i already got all that from alldata

Customer:

can the problem be with the APP sensor?

GM Tech (Cam) :

Ok, I was not sure if you had that. WE always start with the lower numbered code and in this case it is the P1516 so it is the throtle then.

Customer:

plus that test info doesnt help me because i dont know where some of the components are

Customer:

what does it mean "throttle body disconnected"?

Customer:

BTW the blade is fine

Customer:

wait.. what is the blade's proper position?

GM Tech (Cam) :

With the key off, they should sit at about 25%

Customer:

im assuming the rest position is vertical, closed?

GM Tech (Cam) :

It means the throttle body unplugged.

GM Tech (Cam) :

rest should be nearly closed.

Customer:

25% open? it was totally closed when i cleaned it, but moved freely

GM Tech (Cam) :

OK, against spring tension?

GM Tech (Cam) :

let check the amount again.

Customer:

it was tensioned when you moved it, yes, it would close itself

GM Tech (Cam) :

Ok, then that is ok, but the motors and sensors inside are not.

Customer:

so I need a throttle body?

Customer:

or sensors?

GM Tech (Cam) :

throttle body. The sensors are intergral to it and cannot be changed.

GM Tech (Cam) :

check on EBAY if you have time, the parts are often cheaper on there.

Customer:

thats definitely the problem?

GM Tech (Cam) :

I am 98% sure.

Customer:

ok. what do you think about used throttle bodies?

GM Tech (Cam) :

If it works, it is liekly cheaper than new.

GM Tech (Cam) :

I woudl try it.

Customer:

ok. lets see what happens.

GM Tech (Cam) :

ITs worth a shot.

Customer:

do you know if its the same for both V6 motors

GM Tech (Cam) :

no, the belts are different.

GM Tech (Cam) :

Sorry, brain fart,

GM Tech (Cam) :

let me check.

GM Tech (Cam) :

yes, 12609500 is the number.

Customer:

ok, thanks

GM Tech (Cam) :

Is that all for today?

Customer:

yeah, I guess....

GM Tech (Cam) :

Please reply back if you need additional help or press ACCEPT so that the question may be closed out. You can reopen it at any time by replying to it and I will answer ASAP. PLease keep in mind that as experts on this site, we are only compensated for our time spent helping customers once ACCEPT is selected. Thanks again for using Just Answer. Cam.

Customer:

I can check back with you if I need more assistance with this?

GM Tech (Cam) :

absolutly.

Customer:

ok great. Thanks for your help

GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 27664
Experience: GM Grand Master Technician 2007. 11 years experience.
GM Tech (Cam) and 8 other Chevy Specialists are ready to help you

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