So I got a code reader last week because i sporadically kept getting the engine power reduced message, and when I would turn the car off and restart it, it would idle real rough and display engine power reduced. Now I pulled 5 codes when I originally plugged the reader in P0496- Purge Valve, P2135- Throttle/Petal Position Sensor, P2138- TPS sensor, P2176, and P0171. I cleared all of the codes and the car ran fine for about a week and started doing the same thing again. This time only 2 codes were pulled P2135 and P2138. Does anyone know of a fix for these codes? or what the P2176 or P0171 codes are?

Thanks

 

bump

 

Code P2176 = Minimum Throttle Position Not Learned
Conditions for Running the DTC
-The Ignition is ON
-DTC P2176 runs once per key cycle.

Conditions for setting the DTC
-The difference between the predicted and the actual throttle position is more then a calibrated amount
-The above condition is met for more then 1.5 seconds




Code P0171 = System Too Lean
(Fuel Long Term Trim > 20)

Conditions for Running the DTC
-Engine is in Closed Loop Status
-Engine Coolant Temperature (CT) is between 19.4 and 248F
-IAT is between 19.4 and 293
-MAP is between 15 and 100 kpa
-Speed less then 82mph
-RPM between 400 and 6100 RPM
-MAF is between 1 and 512 g/s
-BARO is greater then 72Kpa
-Fuel Level is > 10%
DTC P0171 runs continuously

Conditions for setting the DTC
-The Long Term Fuel Trim Weighted average value is more then a calibrated value (20)
-The above condition is present for more then 2 minutes

 

There is a long list of codes that must NOT be set in order to set P0171, and one of those codes is P2176. I'm guessing that P2176 can cause a lean condition. However P0171 would have had to have been set first, otherwise it would have been inhibited by P2176.

After reading some of the service manual, P2176 only seems to fall under the 2.2L Engine section, however could still be relelvent to the other engines.
Mostly it says to check the throttle valve for binding. Try cleaning it, these cars get dirty throttle valves easily. Also check for loose connections, poor vaccumme hoses ect.

 

DTC 2135 Throttle Position (TP) Sensor 1-2 Correlation
The throttle actuator control assembly has 2 throttle position (TP) sensors mounted within the assembly. The engine control module (ECM) provides individual signal, ground, and 5-volt reference circuits to each sensor. Both sensors operate within a voltage range between 0.35-4.65 volts. When the throttle is opened from 0-100 percent, one sensor signal voltage increases while the other decreases. The signal circuit for TP sensor 1 is referenced to ground, and the signal circuit for TP sensor 2 is pulled up to 5 volts within the ECM.

Conditions for Running the DTC
Ignition is ON
DTC P0120, P0220, P0641, P0651 are not set.
The ignition voltage is greater then 5.23 volts

Conditions for setting the DTC
The difference between the TP sensor 1 and TP sensor 2 exceeds a predetermined value
The above condition is present for more then 2 seconds

DTC P2138 Accelerator Pedal Position (APP) 1-2 Correlation
The accelerator pedal postion (APP) sensors 1 and 2 are located within the acelerator pedal assembly. Each sensor has the following circuits:
A 5-Volt reference circuit
A low reference circuit
A signal circuit
This provides the engine control module (ECM) with a signal voltage proportional to accelerator pedal movement. The APP sensor 1 signal voltage at rest position is near the low reference and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position is near the 5-volt reference and decreases as the pedal is actuated.

Conditions for Running the DTC
Battery voltage > 5.23 VDC
DTC P0641, P0651, P2120, P2125 are not set
Accelerator pedal is leaving the idle position

Conditions for setting the DTC
The voltage difference between the APP sensor 1 and APP sensor 2 exceeds a predetermined value.
The above condition is met for more then 2 seconds

 

The above information was retrieved from some GM Service manuals that I had purchased from a vendor on the site. I hope I didn't violate any copyrights by posting that data.

 

OP put a throttle body on your car and be done with it, P.S. thats covered under powertrain warrenty

 

Thanks for all the info guys! looks like I'll be getting a new TB soon.

 

Bump, so replaced the TB and the problem is still here, I replaced the Evap purge solenoid and put the stock intake back on. All codes are gone except for the p2138 and p2176 codes, I don't know what to do. Should I replace the gas pedal next?

 

bump anyone? I got the p2135 code again today along with the p2138 and p2176. this is driving me nuts, I want to get this fixed already....

 

bump, anyone had this problem before? replaced TB like suggested and still same issues

 

You could of gotten salt water in the gas pedal sensor connectors and created some unwanted corrosion
Which increases the resistance,
Try removing the connectors on the Accelerator pedal position sensors and spray them clean with electrical contact cleaner and inspect them good for corrosion(copper would be a bluish green color when it should be shiny new looking.)
Also do the throttle body connector.

Everything runs on such low voltage that any corrosion creates a resistive issue and can lower the voltage
Enough to create these types of problems.


Also another thing
Make sure the gas pedal is pulled up tight and not dropping down slightly
And dont put your foot on the gas pedal when starting the car.

 

Resently pushing the gas when i start the car is the only way to get it started. If I dont push the gas right away it dies and then when I try to restart it it cranks for 5-10 secs and starts but has that rough idle. I clear the codes and it goes back to normal idle, just engine power reduced mode. Its soooooo annoying. I'm going to clean the connectors tomorrow and see if this helps any. Thank you for the input hopefully this solves my issue finally.

 

Cleaned all connectors and no help, just ordered a new gas pedal off of ebay from a g5 (same one as cobalts) hopefully this will finally fix this situation of mine... Also does anyone know how the wires from the pedal run to the throttle body? are they included in that huge loom that goes across the rear of the engine above the exhaust manifold? I was looking under the hood and noticed that my black conduit is all broken underneath (from the heat off of the exhaust i presume).

 

bump, anyone know where the wires run for the pedal/throttle body?

 

Bump, replace the gas pedal today and it still didn't fix the issue... So far I've replaced the TB and Pedal and still no fix for this problem. I'm thinking there might be a short somewhere between the gas pedal/computer or computer/TB. anyone know where the wires for the system run?

 

Bump, any help?

 

bump, someone? still running like crap...

 

So, I put my old TB back on my car (one it came with) it ran like crap for a few days and now out of nowhere, its running perfectly normal again.

 

makes sence,
there is calibrations inside the PCM as it learns. I dont know what its called, its not in the tune though or a crankposition/cam learn.

 

hmmm, interesting. When I replaced the throttle body the 1st time, it fixed everything for about 2 months, and then out of nowhere it started again. So I replaced the pedal next because I kept getting the code that the pedal position sensor was wrong, no luck with that though. So i said f it and put the old tb back on and now its running fine again. I looked everywhere I could see wire to see if it was grounded or something, but nothing even there. just a picky computer i guess lol

 

I could be wrong, though it was just a thought.