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Ron Z.
Ron Z., - GMC Tech -
Category: GM
Satisfied Customers: 17963
Experience:  18+yrs experience. State Inspector & GM Diagnostics/Repair
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Check engine light on runs fine

This answer was rated:

check engine light on runs fine

May I have the p-codes you received from the scan?

Customer: replied 12 months ago.

ya I was just trying to do that and you were on it. lol. p0172, p0340, p0440

LOL! Yeah, I'm quick this morning! LOL!

Ok, looks like a couple of different problems here. The P0340 is pointing to a problem with the Camshaft Position Sensor. When this sensor has a problem, this can effect the fuel/air ratio, which can in turn set the P0172. So my advice here- work on the P0340 first. So, inspect the electrical connector and wire harness for any loose, broken or damaged wires. Remove the sensor and look inside the hoel to the reluctor wheel. Make sure there are no missing or broken "teeth" on the wheel. If the visual inspection checks ok, replace the Camshaft Position Sensor. See a location view here: https://www.dropbox.com/s/kp5ue6kkmmopypi/cam-sensor.jpg?dl=0

The P0440 is a totally different system. This points to a problem in the EVAP System. This is actually a known issue, and GM has issued a Technical Service Bulletin that states "This may be the result of an EVAP purge valve that is not fully seated in the closed position with the engine off.",. So, carefully inspect the vacuum lines for any cracks, holes or loose connections. Inspect the electrical connector and wire harness. If the these check ok, replace the EVAP Purge Solenoid. See an image location view here: https://www.dropbox.com/s/8dw911ttrxfl8px/evap-purge.jpg?dl=0

Given the close proximity of these sensors, make absolutely sure to inspect the wire harness very carefully. If my answer has helped you, please help me by leaving a rating using the stars at the top of this page or accept the answer so I may be credited. If you cannot rate or do not see the rating stars, please let me know. You can ask follow-up questions after you rate.

Customer: replied 12 months ago.

ok. ive got a few other now to check so I`ll check this one in a couple of days and let you know.

Sounds good. Glad I could be of some help today.

If my answer has helped you, please help me by leaving a rating using the stars at the top of this page or accept the answer so I may be credited. If you cannot rate or do not see the rating stars, please let me know. You can ask follow-up questions after you rate.

Customer: replied 12 months ago.

she drove it today and the light never came back on.

50-75 miles for the 340 and 172. A little longer, with highway driving, for the 440

Hey Randy... how are you making out with this vehicle?

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