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Mike V.
Mike V., Auto Technician
Category: Chevy
Satisfied Customers: 23811
Experience:  25 years automotive experience, Certified Subaru Tech and Nissan factory trained.
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I have a 07 Chev Impala with 3.5L engine non flex fuel. My

Customer Question

Hi Dave, yes I have a 07 Chev Impala with 3.5L engine non flex fuel. My check engine light just cam on about a week ago, and I put my basic code reader on and it comes up with a p0171 code - system too lean - bank 1. I've got about 166,000 miles, never changed any 02 sensors yet. But would I not get an error code for faulty 02 sensors ? Thanks Rick
Submitted: 12 months ago.
Category: Chevy
Expert:  Mike V. replied 12 months ago.

Hi Rick,

The only actual O2 sensor codes are for the heater circuits on them. This code is basically a code telling you what the O2 sensor sees. It sees a lean condition on bank 1. It could be causing it or just reporting it to the computer. Other things can cause the 171 code. An intake manifold gasket leak, the mass air flow sensor and low fuel pressure. In the case of a code like this, it's usually best to use a scan tool that can see the live data and try to make a determination using that as to what is actually failing.

Because its only reporting a bank 1 lean condition, in most cases it can rule out the mass air flow and low fuel pressure as they would affect both banks.

This leaves the front O2, rear O2 and possibly an intake leak as the usual suspects.

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Thank you so much!