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2004 gmc envoy_sle
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My 2004 GMC Envoy service engine light is on for 2 days now. I took it to Auto zone and received the code PO172 (rich code in bank 1). The reduced engine power mode light also came on but turned off. The car has been jerking a bit when you accelerate. I've been reading up on similar cases and it looks like it may be the O2 sensor. Where exactly is this located and if it easy to change? I changed the air filter but that is about it. I want to know where I should start before I take it in and spend hundreds of dollars. Thanks!
 

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the O2 sensor is in the exhaust manifold or just behind in the down tube try pulling it out and run it around the block to see if anything changes if it does u may have a plugged cat, if not try this....

. Check the short term fuel trim and long term fuel trim values at idle and 3000 RPM while in closed loop.

2. The values are normally within +/- 10%, but may indicate negative values if the engine is running rich at the moment.

3. Check the Manifold Absolute Pressure (MAP) sensor voltage at idle. Should have close to 1.0v.

4. Suspect low vacuum if the voltage is over 1.5v at idle.

5. Check and verify the Engine Coolant Temperature (ECT) sensor and Intake Air Temperature (IAT) values in scan data.

6. Check condition of the engine oil.

7. Check the Mass Air Flow (MAF) sensor grams/sec value in scan data.

8. Should have 4-7 grams/sec with engine idling at operating temperature.

9. Verify that the canister purge solenoid is blocking flow with canister purge command OFF.

10. Check the fuel pressure regulator for leak through the vacuum port.

11. If above OK, run injector cleaner through the fuel injectors on the rail, road test.

12. Replace the fuel pressure regulator.
 

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I can't even begin to help because the OP's profile says it's a 6.0L V8 in an Envoy - an impossible combination. If it's an I6, I know my 2004 doesn't have a MAF, but maybe the V8 was different.
 
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