DTC's P0172 and P0175 1997 GMC 5.7 Sierra 1500

CRANK65

MEMBER
GMC C1500

I have a 1997 GMC 1500 with a 5.7 L Vortec and I keep getting DTC's P0172 and P0175. I have replaced the mass airflow sensors twice, new wires, spark plugs and I have just put a new air intake on the truck and had some exhaust work done, new muffler. I was getting the codes before the new intake (AEM brute force intake) and exhaust so I am sure that those parts didn't cause them. Just wondering what steps I need to take to see about getting the problem fixed. I appreciate any suggestions. BTW: The truck has 71,500 miles on it now and I have been fighting with those codes for a few thousand miles now; I keep clearing and they keep coming back.

5 Replies

MVANNESSJR

MECHANIC
223 POSTS

Have you tried disconnecting the battery and letting the computer values reset themselves?

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Friday, March 3rd, 2006 AT 2:59 AM

CRANK65

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4 POSTS

I haven't tried disconnecting the battery, I was using a code scanner and cleared the codes with it. I had read that disconnecting the battery wouldn't reset the codes so that's why I was using the scanner.

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Friday, March 3rd, 2006 AT 9:34 AM

MVANNESSJR

MECHANIC
223 POSTS

That's correct, it may not reset the codes, but disconnecting the battery will allow the computer to re-learn its fuel and air calculations in most vehicles. Try disconnecting the battery for about 5 minutes and then start the vehicle. The computer should take into account the new air/fuel ratios and the problem will likely go away.

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Friday, March 3rd, 2006 AT 2:59 PM

CRANK65

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4 POSTS

I will give that a shot and see what happens. It can't hurt anything that's for sure.

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Friday, March 3rd, 2006 AT 3:22 PM

CRANK65

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4 POSTS

I unplugged the battery cable to let it reset to new values and it worked for a few days but code is back again. I am going to try to take the oxygen sensor off and see what it looks like at the tip, to tell if maybe the engine is really running rich.