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2002 Chevrolet Tahoe 5.3L ZVIN with OBD2 Codes P0172 and P0175 - Fuel Pressure & Sensor Issues

Model: 2002 chevrolet tahoe Fault Code: P0172 Posted: 2010-10-10 08:00

I own a 2002 Chevrolet Tahoe 5.3L (ZVIN) with 76,000 miles. I've already replaced the spark plugs, mass air flow sensor, ignition wires, air filter, and fuel pressure regulator. Despite these repairs, the check engine light has returned—now intermittent. My next suspected issue is the oxygen sensors before the catalytic converters. Can anyone provide guidance on troubleshooting this? Thanks for your input.

Related fault codes
P0172P0175
Comments (8)
Anonymous 2010-10-10 11:24

I suspect either a fuel pressure issue or a converter-related problem. Have you checked if any injectors are leaking down?

Anonymous 2010-10-11 19:14

Fuel pressure reads 50 lbs, which is within the specified range of 48–54 lbs. I don’t have drivability issues. However, I haven’t tested for injector leaks yet. The check engine light is now intermittent. Thank you for your response.

Anonymous 2010-10-12 06:49

According to the D-Tips website, fuel pressure specifications are: KOEO: 55–62 PSI Idle: 45–59 PSI

Anonymous 2010-10-19 09:03

Apologies for the delay. I measured fuel pressure at KOEO and got readings of 38 lbs and 34 lbs—consistent across multiple attempts. The check engine light is now intermittent. I’ve also experienced crank no-start issues. After a no-start, holding the gas pedal down allows the engine to start—but a large puff of smoke comes out afterward, which I suspect indicates fuel or oil flooding. Thanks for your help.

Anonymous 2010-10-19 20:37

Your fuel pressure is too low—this could be contributing to misfires and incorrect air-fuel ratios.

Anonymous 2010-10-23 17:18

The symptoms suggest one or more injectors may be leaking down into the combustion chamber, causing rich mixtures in specific cylinders.

Anonymous 2010-10-25 11:09

First, thank you to everyone who responded. I consulted a repair manual and learned that E85 (ZVIN) engines have lower fuel pressure specifications than gasoline versions—this should have been checked earlier. After cleaning the throttle body, both P0172 and P0175 codes disappeared. However, a new code appeared: P0179 (Fuel Composition Sensor). I suspect this occurred after adding sea foam to clean the injectors. Thank you all again. I’ll update if further issues arise—this may help others with E85-equipped engines. I also realize now that cleaning the throttle body should have been done earlier!

Anonymous 2010-10-28 07:02

I believe this issue is resolved. Upon inspection, I found that the wiring harness for the fuel composition sensor was worn through by the transfer case shaft. After repairing the wiring, the check engine light has remained off. Thank you all for your input—Jeff, Mohawkmtrs, Tomenglish. This experience may help others facing similar issues.