I keep getting a P0170 Code on a Check Engine Light/Engine Electronics ... I looked up the code and it says, "Fuel Trim Malfunction (Bank 1). I don't have the foggiest idea what this means? If you have any clues ... I sure would appreciate your help.

Some background: Car is a 1996 E320 (gasoline 6 cylinder). Mileage is 57,500 miles. All maintenance up to date.

Thanks for your help!

Fuel trim can be caused by vac leaks or fuel pressure regulator.
Pull vac hose off reg and see if it drips/smells gas. If it does , change it.
Also look at all vac hoses ..usual suspects on 104 HFM systems are the white plastic hose going across front of engine , under engine front cover .. they heat fatique and crack..also check the cross hose from MAF for any unmetered air being allowed to enter engine.

Thanks much ... just printed out your recommendations and will do checks as you suggest above.

cpiad

Your interpretation of the fault code must be wrong as it implies you have a V configured engine, ie. bank 1 and bank 2.

Your engine of that year should be a straight 6 engine.

As Arthur Dalton mentioned it should be the 104 engine.

Get somebody who understands better to read the codes and interpret for you.

Regards

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Code P0170 for OB2 is also listed as bank 1 for IL6 engines. Bank 2 would be V engine and the code would be P0173 instead. Same code particulars, but different bank..an IL6 would never have a P0173 code.
They just list it as Bank 1 to cover both IL and V engines.

Ok ... here are checks and actions taken:
- pulled vac hose of the pressure regulator .. slight gas smell ... I am assuming the diaphram may have had it ... so I ordered a new pressure regulator. I assume that all I need is a pair of internal retainer ring pliers to pull the old one out right?
- checked all the vacumm lines I could find ... the lines are all attached and look solid ... no collapses or rubbery feel to them. Engine idles steady as a rock ... so I am going to assume for now that I have no vac leaks.
- On checking the cross-over intake air pipe for leaks/cracks ... I removed the MAF and noticed some fuzzy stuff on the sensor plate ... I cleaned the plate with no-residue electronics component cleaner and dried it with my air compressor ...

I turned the code off ... and after a day ... it came back on. Checked to see it was another P0170 code ... so I decided to get a new MAF along with new pressure regulator. Got both at very decent prices from Autohauz.

I expect the new parts to arrive UPS ground on 9/25 ... so I'll have to wait to install and see what happens. Thank you very much for your advice.

Fuel pressiure regulator can be tested with a fuel pressure test gauge.
However , if gas is evident at vac line , that is a simple verification of ruptured/leaking diaphragm. This fault will make both the pressure at the injectors too high and also allow unmetered gas into the intake through the vac hose. Either will upset the fuel trim , thus the code.

Am I right that all I need is a pair of internal retainer ring pliers to remove the vac regulator? Looks like that's all there is to it.

I have a top-notch vac testing appartus ... pulls vacumm and shows reading ... however, I wouldn't know what is a correct reading from a wrong reading. I suppose I could pull a vac and see if the thing holds it ... I am in the process of obtaining a CD shop manual for the car ... apparently the average consumer can't get a paper manual. Having a manual ought to give me a leg up on the thing. I bought the car new in '96 ... and up until now its been Mr. Reliable ... however, even a car with only 57,600 miles that is 10 years old going on 11 will have issues ...

There was a minor hint of fuel smell coming from the vac line, and that's enough for me to assume the diaphram or an internal seal is shot. There's not much to that pressure regulator. Both parts (MAF and pressure reg) came out to about $300.00. I could have spent that much at a dealership and not gotten much beyond getting the code read ... so, I figure throw a few dollars at it and see if the problem goes away. Thanks for staying with me on this ... really appreciate your help and willingness to share your expertise with a neophyte.

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Yeah....... after you release any fuel rail pressure at the service port.