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Old 02-22-2021, 12:44 PM   #5
mikeinoki
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Join Date: Feb 2016
Location: North Carolina
Posts: 9

2007 VUE Green Line
Default Re: 2007 vue greenline 98000 miles P0121 code

This is an old thread but I wanted to add some information about the P0121 code. On many vehicles this code is caused by a dirty throttle body. My 2007 Saturn Vue Green Line has 257,000 miles and recently threw this code.

This vehicle has a drive by wire throttle body, meaning there is no throttle cable. The throttle is operated by a small motor and has a throttle position sensor to measure how far it is open. These components are built into the throttle body and cannot be individually replaced.

There are two accelerator pedal position sensors that the computer reads. These sensors are built into the accelerator pedal as a single component and cannot be individually replaced. The computer uses these measurements to signal the throttle position motor to open or close and the throttle position sensor as feedback to measure how far it is actually open.

Blowback gunk from the PCV system can build up in the throttle body in the bore around the edges of the throttle plate and on the plate itself, especially on high mileage vehicles. Over time the computer compensates for this buildup by opening the throttle plate a little more. Eventually this change becomes large enough to read as a discrepancy between the throttle position and the accelerator pedal position. This will throw the P0121 DTC.

To clean the throttle body, do NOT remove it from the vehicle. Remove the plastic air intake. NEVER, NEVER, NEVER try to manually turn the throttle plate. You will destroy the throttle body.

Turn the key on, engine OFF. Have someone press the accelerator pedal or lay something heavy against it to set the throttle wide open. Only use throttle body cleaner to clean the throttle and plate. I used the CRC brand. Use a soft toothbrush and paper towels to clean the throttle bore and plate. Clean the throttle plate gently, it has a protective coating to help repel gunk. That is why you should only use throttle body cleaner. You can carefully blow it dry with some compressed air. You might want to use goggles or glasses to keep it out of your eyes.

Reassemble the plastic air intake and start the car. It will run like crap. The computer will have to relearn how to operate the throttle plate in the clean throttle body. Without having to take this to the dealership, the relearn procedure is to let the car idle for 3 minutes, then turn it off for 60 seconds. Repeat this procedure one more time. Then drive the car at speeds above 44 mph using several decelerations and accelerations. You will need to repeat the entire process several times.

Mine took about 2 days to get a decent idle when first started. The idle was very rough after driving and had hard downshifts due to the RPMs running a little high. The computer may throw some new DTCs related to high RPMs or air intake during this process. Ignore them, they can be cleared later. It took a full week of driving to complete the process but mine now idles and drives very smoothly. My throttle plate has gone from idling at around 28% open down to around 15%, depending on temperature, and no more DTCs.

I highly recommend anyone working on their vehicle to get the Torque Plus app for five bucks, and a Bluetooth OBD2 adapter. I bought a cheapo ELM327 adapter a few years ago for five bucks that works okay, but sometimes has connectivity issues with certain vehicles. I recently bought a BAFX OBD2 adapter for around $18 on Amazon that works really well. You can read tons of sensor data and read and clear DTCs with Torque Plus. It works with any Android device. I will include a couple of screenshots of the before and after data using Torque Plus and my smartphone a little later.

DISCLAIMER: I am not a professional mechanic. Use common sense. Throttle body cleaner is flammable. Try this stuff at your own risk. If you destroy your car or you are blinded, maimed or killed, then better luck next time.

Last edited by mikeinoki; 02-22-2021 at 12:50 PM.
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