Mechanics

PO172 AND PO 175

1997 GMC C1500

Engine Performance problem
1997 GMC C1500 V8 Two Wheel Drive Automatic 162000 miles

I keep setting both bank 1 and bank 2 rich at the same time
I can erase the mil and drive non stop and the codes will never show up except in pending codes but as soon as I turn the engine off the codes will show up
i have replaced the o2 sensors, the maf is with in limits, fpr is replaced, fuel pressure is good,
when these codes are set my gas milage goes down to about 10mpg when the codes are set I get about 19 on the highway.
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Cobra1
October 23, 2008.




Hi cobra1 and welcome to 2carpros

P0172/P0157-rich codes

Could be a bad O2 sensor, excessive fuel pressure (bad fuel pressure regulator or plugged return line), leaky fuel injectors, dirty air filter or restricted air inlet, or a defective coolant sensor that prevents the engine management system from going into closed loop mode.

Tiny
Rasmataz
Oct 23, 2008.
I have changed or checked all those items and they are all good
could the pcm cause the problem of both codes being set at the same time
AD

Tiny
Cobra1
Oct 23, 2008.
I have changed or checked all those items and they are all good-Your last stop is the computer-however double checked the items again something is making it go rich-how about the O2 sensor is it switching -

Tiny
Rasmataz
Oct 23, 2008.

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