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Jared D
Jared D, ASE Certified Technician
Category: Chevy
Satisfied Customers: 1863
Experience:  Shop Supervisor at County Fleet
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I have 2007 chevy Silverado 1500LS First I have a code PO121

Customer Question

I have 2007 chevy Silverado 1500LS First I have a code PO121 so I clean the throttle body when I start it the idle is high I have been driving it for how many days now. Now I have another code PO 449 any suggestion I'm trying to fix it myself
Submitted: 5 months ago.
Category: Chevy
Expert:  Jared D replied 5 months ago.

Good evening.

When you cleaned the throttle body was the key in the on position?

You may need to reset the throttle position sensor. This is easiest with a scan tool, but can be done manually.

As for the p0449 this code indicates a faulty evaporative canister vent solenoid. Have you replaced that solenoid before?

Customer: replied 5 months ago.
The is in off position and I took the throttle body out and I did not replace the solenoid before how much you think that cost to purchase
Expert:  Jared D replied 5 months ago.

At this point you will likely need to perform a throttle position relearn with a scan tool, or reset the throttle position manually to get the idle back where it should be.

The vent solenoid is fairly inexpensive- about $30 for the part at most parts stores.

Customer: replied 5 months ago.
How do you re learn the throttle manually I just bought a scan tool
Called blue driver I can read and clear codes
Expert:  Jared D replied 5 months ago.

Your best bet would be to try disconnecting both battery cables and hold them together for about 1 minute. This will clear the memory in computer controlled modules. Then have someone hold the throttle plate closed while you reconnect the battery cables. This will set the closed position for the throttle body. Make sure the key is off the entire time.

Customer: replied 5 months ago.
I don't have any more engine light on but still idle high. I drove it once put it on park it will go up to 2000 rpm.
Expert:  Jared D replied 5 months ago.

It sounds like you still have something wrong in the throttle body or a correlation problem between the throttle body and the pedal position sensor.

Will your scan tool perform the relearn? Most basic scan tools won't.

Customer: replied 5 months ago.
No it won't do relearn. When I start it in the morning or after I rest it idle better about 600 rpm but after go for a drive and park it will idle high 2000rpm. If I put a new throttle body can I relearn it manually
Customer: replied 5 months ago.
Any recommendation on scan tool
That will do relearn and affordable
Expert:  Jared D replied 5 months ago.

There are none that I can think of that would do it inexpensively. Are you seeing any trouble codes stored at this point?

Customer: replied 5 months ago.
Nope I just scan it no codes. It's running fine right now once I take it for a drive and park it will idle high again
Expert:  Jared D replied 5 months ago.

Let me see if chevy has any ideas on this one.

Expert:  Jared D replied 5 months ago.

According to chevy that is a sign of the throttle body needing replacement. There is a problem that develops in the actuator where it won't return to closed once the vehicle is warmed up.

Customer: replied 5 months ago.
Can I replace it myself and do the relearn manually
Expert:  Jared D replied 5 months ago.

It would be best to use a scan tool, but you could try the manual re-learn. It wouldn't hurt anything if it doesn't work. You would just need to run it to a shop that can do the programming. It would most likely start and run, but the idle would be off and the check engine light would be on.

Customer: replied 5 months ago.
Okay thanks I appreciate all the help
Expert:  Jared D replied 5 months ago.

Let me know how it goes if you decide to replace the throttle body.

Expert:  Jared D replied 4 months ago.

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Let me know if you need additional info.