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Dan
Dan, Technician
Category: Chevy
Satisfied Customers: 23682
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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I get Throttle position sensor code P0121 on my Chevy Tahoe.

Resolved Question:

I had a TPS code p0121 on my 2007 Chevy Tahoe. I cleaned the throttle body on the vehicle and the code went away and never came back for 3 days. Only problem now is I have a high idle and can't figure out the problem.

Submitted: 7 years ago.
Category: Chevy
Expert:  Dan replied 7 years ago.

Clean the throttle body with some approved cleaner from your local parts store. Then perform the following relearn procedure. When done, your problem should be taken care of. You can also get some approved cleaner to clean the mass airflow sensor. Let me know if you have questions. Thanks

1. Perform a Throttle Learn.

2. Start and idle the engine in park for 3 minutes.

3. With a scan tool, monitor desired and actual RPM.

4. The Electronic Control Module (ECM) will start to learn the new idle cells and desired RPM should start to decrease.

5. Ignition off for 60 seconds.

6. Start and idle the engine in park for 3 minutes.

7. After the 3 minute run time, the engine should be idling normal.

8. If the engine idle speed has not been learned, the vehicle will need to be driven at speeds above 70 km/h (44 mph) with several decelerations and extended idles.

9. After the drive cycle, the engine should be idling normally.

10. If the engine idle speed has not been learned, turn off the ignition for 60 seconds and repeat step 6.

Customer: replied 7 years ago.

Do I need a scan tool?

Expert:  Dan replied 7 years ago.

No, it is just preferred to monitor rpm, but you can do that by just watching rpm on the dash also. Let me know if you have more questions. Thanks.

Customer: replied 7 years ago.

Idle seems ok now, but when driving, say going 20mph or more and if I shift into neutral to see the idle, the rpm is going up to 2500-3000rpm. When starting the vehicle, the idle is good but when shifting into drive or reverse and let off the brake, the truck really wants to move with out touching the gas pedal.

Expert:  Dan replied 7 years ago.

Try the relearn procedure again. If the problem still exists, my next step would be to replace the idle air control valve/motor. Let me know if you have questions, Thanks.

Customer: replied 7 years ago.

Where is the iac on this 2007 Tahoe?

Expert:  Dan replied 7 years ago.

Never mind, this year does not have the idle air control valve/motor. The problem is most likely the mass air flow sensor or throttle body. You can clean the mass airflow sensor to see if that helps and perform the relearn procedure again. If problem still exists I would bring the vehicle to a shop with a high end scan tool. So they can monitor mass airflow sensor operation to determine if the problem is that, or the throttle body. They could also reprogram the pcm. Let me know if you have questions. Thanks.

Dan and 5 other Chevy Specialists are ready to help you
Customer: replied 7 years ago.

Thank you. I will try the procedure again. If not, I will take to dealer.

Expert:  Dan replied 7 years ago.

Ok, let me know if you need anything. One of the above things are the cause of the problem, but the dealer only has the equipment to know exactly which one. Thanks

Customer: replied 7 years ago.

Thanks again..