2002 Outback 2.5L H4 Auto w/ p0172 CEL code

[5bgeorge]

I have a 2002 Outback 2.5L H4 Auto with approx 125k mi on the engine and 145kmi on the chassis and I am getting a p0172 Check Engine Light code - right bank rich -with intermittent symptoms: hesitation on cold warm up is the main one...have run several fuel ' injector cleaner treatments over the last 4500 mi and have switched to non-ethanol premium gas - both of which have temporarily resolved the symptoms and shut down the light...but now am getting a very small front crank seal oil leak.... the dealer in Boise will charge $50 to run down the diagnostic check on the code and said they could pinpoint the faulty part, which, when diagnosed with a non-dealer device reveals several possible culprits. Looks like I will have to do a timing belt/front crank seal replacement...the H20 pump only has 50k mi on it, but will probably replace that too?

Does anybody know if the dealer's claim is valid, as if it is, I'll drive the 200 mi and pick up the part...but I'd rather not roll the dice if the service desk isn't being completely forthcoming.

Thanks.

Any references on best place for parts source?

[5bgeorge]

oops...have to get to a job, will check the forum later! thanks for any response!

[plain OM]

With the right equipment it might be possible to narrow down the cause of the P0172. The Subaru Select Monitor is probably what the dealer would use; however, there are other similar devices ("scanners") that, while expensive for the average DIYer, other shops might have.

Regardless of the device used, it won't make readings and pop up a window saying "change xxx" as if xxx is the precise reason for the problem. Instead, the equipment is more likely to display a number of selected parameters (sensor signals etc) and it's up to the mechanic to interpret them. So the key, whether at the dealer or another shop, is understanding what the data is indicating; in other words, the knowledge and skill of the person reading the information.

P0420 Diag is an example where a particular code, P0420, which is often used to justify changing the catalytic converter in the exhaust system, was found to be caused by something far simpler.

[1 Lucky Texan]

if you're asking about on-line parts houses, I've done the most biz with subarugenuineparts.com (email Jamie through there for special/odd questions - they are a dealership)

I've ordered stuff from Fred Beans and from ebay and from RockAuto and even amazon.

[5bgeorge]

Thanks for the replies...at this point, I've done two non-dealer code diagnoses - both read the same code with the same series of possible "fixes", so I am ready to try a dealer diagnosis. If the dealer can pinpoint or target a specific part for replacement, I'll pick one up and give it a go...if not, well, I'll take that up with the service desk after the diagnosis. I'll pick up a new fuel filter and PCV valve just because they're probably due, and tackle the oil seal soon. If anyone else has had a p0172 code problem resolved, I'm still interested....

[1 Lucky Texan]

T hink you should consider the plugs and wires. Though i don't know why you wouldn't get a misfire code, a misfiring cylinder could allow too much unburned fuel through. Might explain the poor idling and would be 'bank specific' I think. Soobs prefer NGK plugs and OEM (or, at least, parts store BEST wires)

but I suspect many problems could lead to the code you have.

[cardoc]

The ECM is reporting high fuel mixture in the exhaust. This can be caused by worn plugs not burning the mixture fully in the combustion, the AF sensor, the one one front of the CAT, is reporting false information, faulty thermostat or MAF.

Given your mileage, I would guess at worn plugs. When the plugs wear down the spark changes and reduces the ability for the burn in the combustion to occur effectively. Plugs are due every 60k for severe driving or 100k for average.

My next guess would be the thermostat is sticking partially or fully open not allowing the engine to come up to temperature. Where is your temp gauge residing after driving for a while? Thermostat life is on average 60-75k miles depending on average ambient temperatures.

Review your service records and go from there. If you are overdo for either, start there, clear the codes and see what happens.

[5bgeorge]

Thanks for the suggestions! Took the car to the dealer (Larry Miller, Boise) and went for the diagnostic check...which revealed that the ECM was due to have an update - from an A setting to an E setting...a "reflashing" of the software. The update cleared the CEL and the p0172 code (which was stored in its memory). The engine sat at idle for 5 min in the bay, and "data looks OK"... The suggestion was to drive the car and see if the CEL light comes on again...if so, the most likely culprit would be the A/F sensor, which I'll purchase if that CEL shows up again. I drove the car the 200 mi home and discovered that it was having some trouble idling in Drive...so I'm set to change out the Fuel filter and PCV valve and give it another go...if that doesn't resolve the idle issue, I'll be going back to the dealer for ... another ECM reset? In any case, the Service Dept there did a first rate job! Waived the diagnostic fee in lieu of the ECM reset charge ($69.30) and I was able to go into the bay and talk with the mechanic (Doug) who suggested that the oil leak under the timing cover was more likely due to a leaking crankcase access port plug (one on each side of the front bottom of the crankcase, to access the rod bearings on each bank) and may need a new washer seal.... Better than having to pull the front crank seal and not stop the leak. More to follow....

[5bgeorge]

Also, This engine has new plugs and wires 25K mi ago and the temp gauge seems to be consistently showing appropriate operating temp...although I'll put in a new thermostat when I replace the timing and accessory belts and water pump.

[cardoc]

Originally Posted by 5bgeorge

Thanks for the suggestions! Took the car to the dealer (Larry Miller, Boise) and went for the diagnostic check...which revealed that the ECM was due to have an update - from an A setting to an E setting...a "reflashing" of the software. The update cleared the CEL and the p0172 code (which was stored in its memory). The engine sat at idle for 5 min in the bay, and "data looks OK"... The suggestion was to drive the car and see if the CEL light comes on again...if so, the most likely culprit would be the A/F sensor, which I'll purchase if that CEL shows up again. I drove the car the 200 mi home and discovered that it was having some trouble idling in Drive...so I'm set to change out the Fuel filter and PCV valve and give it another go...if that doesn't resolve the idle issue, I'll be going back to the dealer for ... another ECM reset? In any case, the Service Dept there did a first rate job! Waived the diagnostic fee in lieu of the ECM reset charge ($69.30) and I was able to go into the bay and talk with the mechanic (Doug) who suggested that the oil leak under the timing cover was more likely due to a leaking crankcase access port plug (one on each side of the front bottom of the crankcase, to access the rod bearings on each bank) and may need a new washer seal.... Better than having to pull the front crank seal and not stop the leak. More to follow....

Really???? Data looks okay but drive it and see if it comes back on???

Who serviced your car?

I think the dealerships are so hard up for profit they may be hiring right out of shop class at the local high school for lunch money.

If the car is indead running rich, try Sea Foam to clean the fuel and injectors.

If the AF sensor is reporting rich, then the ECM would reduce the fuel trim accordingly to bring it back to Stoich.

If after many tries at altering the fuel trim and it still sees a rich value, it sets the code.

So, look for loose or broken vacuum lines, listen for a "whistle" at idle and pull the plugs and see what color the tips are. Beyond that, you would need a scan tool to be able to see the data. It could be a fault in the AF sensor. Could also be crappy gas like Murphy.