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Gary
Gary, ASE Certified Technician
Category: GM
Satisfied Customers: 740
Experience:  Senior Technician
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I replace the upstream and downstream sensor of my Chevy

Customer Question

i replace the upstream and downstream sensor of my Chevy impala 2009. and the check engine lights still on even the gas cap , i replaced it with the new one, I don't know why the check engine lights still on, even i disconnect the 2 terminal battery, yes the lights off but when the car running for about 2 to 3 miles the lights comes on again, i don't know what to do.
JA: Does the light stay on, or does it blink?
Customer: it's on steady
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: i bring the car to the mechanic shop, but they can't trace or diagnose the real problem.
JA: Anything else you think the mechanic should know?
Customer: they said the air box is not closed enough that why there's a vacuum leak in the housing, then i order a lid box n line and i replaced the old one but still the same the lights still on,i' m spending much money for nothing on this matter.
Submitted: 3 months ago.
Category: GM
Expert:  Gary replied 3 months ago.

Hi there,

Can you give me the code that sets when the engine light comes on?

Your mechanic is guessing about things like the airbox lid.

You may need to take it to a better workshop.

Gary

Customer: replied 3 months ago.
P0171& p0172
Expert:  Gary replied 3 months ago.

What engine in your car?

I will come back with some more info shortly.

Gary

Customer: replied 3 months ago.
3.5 6 cyl. Lt
Expert:  Gary replied 3 months ago.

Ok, I'll be back soon.

Gary

Expert:  Gary replied 3 months ago.

Hi there,

There are many reasons for why and how this may happen.

Here is the diagnosis for P0171 and P0172, as a start.

Do they have a GOOD scan tool to observe O2 sensor activity?

Gary

Expert:  Gary replied 3 months ago.

Hi again,

Do you need any further help?

I hope my advice has been of assistance to you.

Kind regards

Gary

Expert:  Gary replied 3 months ago.

Hi again,

How did you go with your problem?

I hope my advice has been of assistance to you.

Kind regards

Gary