Po 171 & 174 codes
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Joined: Jul 2011
Posts: 85
Likes: 18
From: Columbia SC
Po 171 & 174 codes
Ihave a bone stock 2001 C5, just turned 100,000 miles. It started throwing the PO171 & 174 codes. When I first looked under the hood one of the clamps on the air filter housing was loose. I cleaned the K&N filter element & cleared the code. The codes came back so I put in a stock air filter, cleaned the MAF & checked for leaks from the air filter to the throttle body. I looked for vaccum leaks as well. Cleared the codes. Now if I start the car cold and drive 10 miles or 100 miles the light does not come on as long as I don't shut the engine down and restart it hot. ANy time the engine is restarted hot the check engine light immediately comes on. I bought a new fuel filter to put on this weekend. If that doesn't work, my next step is to take it to the dealer unless y'all have some other suggestions.
Melting Slicks
Joined: Jul 2012
Posts: 2,507
Likes: 9
You need to get a scanner on it and check the output of the O2 sensors and the ST and LT fuel trims. My truck was throwing these codes and my front O2's were very lazy and the Fuel trims were at their max. Replaced the O2's reset the fuel trims and all is well.
Drifting
Joined: Sep 2009
Posts: 1,719
Likes: 4
From: cinnaminson n.j.
St. Jude Donor '14
If you don't find any vacuum leaks, Freeze frame data would be a big help. Come inexpensive scanners will provide it. If it set at idle, you probably would notice it running a little rough on initial cold start until front o2's are hot enough to function. You can use carb cleaner or propane to find the leak if looking and listening didn't. If the freeze frame data shows tps of 8% and more than about 1200rpm then it's probably the MAF sensor.
The fuel filter could also cause a part throttle lean condition, but if that was the case the car would just lay down at full throttle.
The fuel filter could also cause a part throttle lean condition, but if that was the case the car would just lay down at full throttle.
Team Owner
Joined: Sep 2003
Posts: 20,179
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Read this on another forum....
Anyone?
you should turn the ignition on but keep the motor off, remove fuses 16 and 23, then turn the ignition off, and replace the fuses.
These codes basically result from unmetered air bypassing the MAF. Removing the fuses will reset to baseline numbers and allow the computer to "learn" the new mixtures.
These codes basically result from unmetered air bypassing the MAF. Removing the fuses will reset to baseline numbers and allow the computer to "learn" the new mixtures.
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