Code P0175 96' C1500

[SoCalSlaughter]

I recently bought a 1996 Chevy C1500 5.7. Its pretty clean, all stock. Runs and drives fine. I have to smog the truck soon in Cali, and the computer keeps giving me a P0175. I decided to give the truck a tune up, all new O2 sensors, spark plugs and wires, dizy cap and rotor and new air filter. Reset the computer and take the truck for a drive, and after about driving for 15 minutes, the CEL comes on again with the same code. Did a Live data read of all the O2 sensors and they are all operating correctly. The truck runs fine, but it wont pass smog if the light is on. Any ideas on what i can check on? test? replace? Thanks guys!!

[88Ironduke]

I would say to start with the basic systems that must be verified in order before troubleshooting. Provided the trucks runs good, makes decent power and isn't misfiring. Has no unusual oil consumption, smoke at start up, while idling, under heavy load etc been going on? If basic systems are running amuck the narrow parameters of operation the computer logic must live within will the kick on the check wallet light quick.

Ignition systems, plugs wires, cap/rotor. It looks like most of that has already been done. Ensure that if applicable that the plugs are gapped correctly. I would keep the O2 sensors you removed as they are most likely still serviceable.

Engine temp, is the engine getting to operating temperatures properly? A lower temp thermostat or removed thermostat can drive this condition because the engine never gets to full operating temp. Bear in mind the temp gauge on the dash may or may not be completely accurate. If your scan tool gives that data up you're in. If not, trust the gauge is working but verify proper temp.

Check for proper fuel pressure on the fuel rail, I assume this is not a throttle body and has 8 injectors or a spider assembly in the manifold. A bad fuel pressure may be driving too much pressure or not enough causing incorrect spray patterns or dribbling. A cylinder that is running ok but not burning properly will show itself on a spark plug. If a plug shows fouling that cylinder and or bank is your culprit. This can set off the code you are shooting.

If all external stuff is good, it is very possible that you have a leaking injector/spider assembly buts its very expensive to trouble guess that stuff. Verify what you can.
Good luck.
88Ironduke

[cableguy0]

Leaking spider injection or regulator under the intake is the most likely cause. Get the new upgraded assembly that replaces the problematic older style setup.

[Chevydude56]

This might help

http://troubleshootmyvehicle.com/gm/...d-P0175-page-1

[SoCalSlaughter]

Thanks guys, I had the top plastic intake off last night and was inspecting the FPR, and its not leaking, vacuum tested it also and it holds pressure. I did notice there is an excessive amount of carbon build up, in some parts of the intake, its almost 1/4" thick. Ive inspected the exhaust for leaks, none found. Once I put everything back together, I road tested the truck and it got a code for the MAF saying low signal, and high signal. Ive only driven the truck since I put it back together for maybe 10 miles. This light never came on before. And I never unplugged the MAF or removed it from the intake, just the tube that goes from the MAF to the manifold. What a pain!

[cableguy0]

A bad MAF can also cause your code just make sure to check the wiring. A lot of gm vehicles have an issue with the MAF harness shorting which kills the MAF. A new Pigtail harness is never a bad idea though. Most of those engines I have torn down are cruddy under the intake.

[SoCalSlaughter]

I'll have to check out the wiring when I'm off work. The strange thing is, eveyrhting I look up on this code, is always with code P0175 AND P0172. But I only have the bank 2 code. I did have an O2 sensor code, but that was for Bank 1 senor 2, and I've replaced the O2 and reset the ECM and now only the P0175 is active. Wouldnt a faulting MAF throw a code at the same time as the P0175?

[cableguy0]

Not if you haven't completed all the drive cycles. Your biggest issue is the lack of drive time. It takes a while for the computer to go through all the systems and check everything. Usually dead faults will show first.

[53burb]

I just ran thru all of this a couple of days ago....very frustrating!!

http://67-72chevytrucks.com/vboard/s...d.php?t=623620

maybe mine will help....