2007 GMC C1500 Engine codes PO171 & PO174

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  • 2007 GMC C1500

Computer problem
2007 GMC C1500 6 cyl Two Wheel Drive Automatic 69000 miles

I had the 60k service done at 66k and the engine light came on the next week. The mechanic at the Tire Barn said it was either the fuel pump or the catalytic converter, then turned the code off. Since I drove it in without problem he said to bring it back when they come on.
When the engine light came on again he said it was the catalytic converter and to take it to the dealer since it was under warrenty till 80k. The dealer first had to run their own diags and said it was dirt in the injectors and wanted 139.99 to clean them. I told them I just had it serviced. I called the Tire Barn and the mechanic said he would re-do it at no charge.
When the engine light came on again the Tire Barn mechanic said without any problems in drivability it is hard to determine whether to change the fuel pump or the converter, or even clean the o2 sensors.
Do you have any info that will help solve this problem

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Wednesday, July 15th, 2009 AT 5:20 PM

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2007 GMC C1500 Engine codes PO171 & PO174

A lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (Use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (Try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)

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Wednesday, July 15th, 2009 AT 7:20 PM

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