po172, system too lean bank one, code keeps coming up. i have cleaned the MAF sensor, installed a new air filter, cleaned my EGR valve!! code continues to come up!! any advice? i did all these things one day and the light went off when i was going to scan my truck to see if it was going to go away. now in my process of going to the auto store the light went out!! scanned it anyway and NO codes were shown!!! go figure!!! help!!
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1996 Chevrolet 2500 Pickup Question: code po 172 keeps coming up! tried to fix it, no luck yet!!
PARTS GUY December 15, 2011, 19:41Master
Tests/Procedures: 1. Check fuel pressure at idle and under load. Idle pressure should be about 55-57 PSI. Loaded fuel pressure should climb to about 60-65 PSI.
2. Verify the Coolant Temperature Sensor (CTS) is accurate.
3. Check the Mass Air Flow Meter (MAF) for about 4-7 Grams Per Second (GPS) at idle.
4. If all OK, remove the plenum, check for intake "washing" caused by a leaking fuel pressure regulator.
Of course you need a scanner that can read serial data to see these specs.
Replythor1779, December 19, 2011, 19:38Rookie
do you think that i might still have some oily residue built up on the inside of my air cleaner hose? i was using a k&n filter in it and over-oiled my filter. going to clean it out with some brake cleaner and try that too.
just curious too, where ion the heck is the coolant temperature sensor located on my truck. never even heard of this!
Answer #2mastertech6371 December 15, 2011, 20:47Master
172 is a rich code, not lean. items like clogged air filters, leaking injector, mass air flow, coolant sensor are some possibilities. you need a shop that can acess the history codes and freeze frame data to see which sensor is reading out of spec and give you a solution.
ReplyPARTS GUY, December 19, 2011, 20:38Master
Roy I think Thor1779 answered his own question. He needs to clean the oil film off the Mass Airflow Sensor. K&N oiled air filters are bad for vehicles that have a volumetric (MAF) fuel metering system. AMSOIL sells a better flowing air filter than K&N and doesn't use oil.
Replymastertech6371, December 20, 2011, 07:20Master
thats why i tell people never, never use those k/n filters. they cause way too many issues.