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Old 11-06-2008, 05:56 PM   #1
cboss
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Default ODB II Codes Solutions - P0172 (your experience needed)

I have found the info about computer codes in the forums lacking in one critical area. While comments are made about what "could" cause the problem, few posts discuss the actual solutions finally found.

I would have to think that some specific causes are more "common" that others are. Also some causes finally found, may not even be mentioned in the official lists of what could cause a specific code to be set.

This post is to discuss the final solutions actually found for those who experienced the dreaded P0172 (bank 1 rich) code. If this experiment is found to be helpful to others, then other codes can be posted in other threads.

If you ever experienced the dreaded P0172 code with your Saturn (any model/year) and finally solved the problem (or a mechanic solved it) please post your experience here, what the final solution was and how you found that out.

This thread is not for discussing the P1072 code, so don't post here. It is simply to document those who experienced it and finally fixed it and how.
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Old 11-06-2008, 06:35 PM   #2
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Default Re: ODB II Codes Solutions - P0172 (your experience needed)

Out of range high fuel pressure. Caused by using an aftermarket filter/regulator.
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Old 11-07-2008, 03:52 PM   #3
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Default Re: ODB II Codes Solutions - P0172 (your experience needed)

Both the Fuel Filter/Regulator combos and the standalone Fuel regulators which are aftermarket appear to have this problem.

I bought a fuel regulator (96 SL2) at Advance and it ran 5 psi higher than the OEM, a good bit above the accepted range for this car.
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Old 11-07-2008, 10:28 PM   #4
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Default Re: ODB II Codes Solutions - P0172 (your experience needed)

What would also be useful in this thread, would be explained what tests were used to find the cause of the richness.

On my car (96 SL2), I used a fuel pressure gauge. Mine cost $40 at Advance, but you can purchase cheaper ones online.

The fuel pressure regulator I installed (from Advance) ran at 40 psi, while the original ran at 35 psi. There was a vacuum leak which caused the original to have too much pressure (which is why I installed a new one), but once the vacuum leak was fixed and the old FPR was installed back, I got the pressure down to 35 psi (the range should be from 31 to 36 psi).

Testing fuel pressure is very easy to do.
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Old 11-07-2008, 10:46 PM   #5
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Default Re: ODB II Codes Solutions - P0172 (your experience needed)

It is actually a very easy code to troubleshoot. You just have to go from the most likely cause to the least likely. A fuel pressure tester is required or you are done though. A good scanner helps also.

My book is out in the garage and its snowing. But before you can set a 172 there is a long list of codes that must not be present and only a short list of possible causes.

DTC PARAMETERS
DTC P0172 will set if the averaged long term idle and cruise fuel trim cells are 101 and the current short term fuel trim cell is below 128 for three seconds when:

* PCM is using the non-purge long term fuel trim cells.
* The system is in closed loop.
* Engine coolant is between 60 and 115C (140 and 239F).
* Air flow is between 2 and 80 grams/second.
* Manifold pressure is between 20-90 kPa (3-13 psi).
* RPM is between 500-4000 rpm.
* TP is less than 75% open.
* Barometric pressure is greater than 70 kPa (10 psi).
* IAT reading is between -30 and 80C (-22F and 176F).
* Vehicle speed is less than 121 km/h (75 mph).
* No ECT MAP, IAT TP Sensor, VSS, EVAP Cannister Purge, Front O2S or P0125 DTCs have been set.

IMPORTANT: The fuel control system is continuously checked when the above conditions have been met.

Possible Causes
The following are malfunctions that could cause a rich condition:

* Fuel pressure too high. Perform fuel pressure test. (Refer to "Engine/Fuel/Air Intake/Exhaust Service Manual" for procedure on pressure check.)
* Leaking fuel injector(s). - Perform pressure leakdown test. (Refer to "Engine/Fuel/Air Intake/Exhaust Service Manual" for procedure.
* Vacuum leak around the MAP sensor grommet.
* Oxygen sensor contamination.
* Restricted exhaust or air intake.
* Fuel Vapor Canister saturated with fuel. (Refer to "Engine/Fuel/Air Intake/Exhaust Service Manual.")

IMPORTANT: If the front oxygen reading voltage is above 600 mV and the rear HO2S is above 600 mV all the time, the O2 sensors are probably not at fault.
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Old 05-20-2013, 08:49 PM   #6
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Wrench Re: ODB II Codes Solutions - P0172 (your experience needed)

I had the dreaded P0172 code on my 2001 Saturn SC2 and I bought TWO aftermarket filter/pressure regulators and BOTH caused my fuel pressure to run around 55 PSI which is just at the maximum allowance for the pressure on my car. After screaming at my car for an hour while drinking beers late at night and sleeping off the booze and pent up rage, I went to the dealer to purchase the GM brand filter/regulator for about 150 dollars. After I placed the GM filter on the car, the code went away. The two aftermarket brands were Purolator and something from Autozone and they were both cheap. Regardless, only only only only buy the dealer filter/regulator! Actually I think I will only buy dealer-brand sensors after this freaking mess.
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Old 05-20-2013, 11:02 PM   #7
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Default Re: ODB II Codes Solutions - P0172 (your experience needed)

The WIX 33731 or the NAPA equivalent filter regulator works well also and rock auto sells it or this place sells them http://www.usafilterstore.com/ or here, http://www.usafilterstore.com/mm5/me...duct_Code=3731

~$33.00+ shipping.
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Old 06-11-2013, 01:25 PM   #8
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Default Re: ODB II Codes Solutions - P0172 (your experience needed)

I had the combination of P0172 and P0175 system running too rich, and it turned out that the clamp AFTER the MAF sensor and before throttle body was on crooked an leaking air. Also another problem was that the oil level was way too high. There was engine oil running out from the throttle body outward through the MAF and onto the paper air filter. There was a small puddle of oil on the bottom of the air filter box.
So anyone finding these code combos should check these two things.
1. Oil level
2 Air leaks after MAF

Cheaper then going after new sensors.
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Old 07-26-2016, 10:49 PM   #9
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Default Re: ODB II Codes Solutions - P0172 (your experience needed)

Just finished Diagnostics on a 01 SC1 with the P0172 code and poor performance off idle and under load. End result was restricted exhaust flow through the catalytic converter that's built into the exhaust manifold.
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Old 07-26-2016, 10:55 PM   #10
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Default Re: ODB II Codes Solutions - P0172 (your experience needed)

Quote:
Originally Posted by Shaw18 Racing View Post
Just finished Diagnostics on a 01 SC1 with the P0172 code and poor performance off idle and under load. End result was restricted exhaust flow through the catalytic converter that's built into the exhaust manifold.
Quite common problem with the preCAT. Best approach is to rod it out completely and be done with it.
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