Need Help with my truck - PeachParts Mercedes-Benz Forum

Mike Michalek · #1 04-11-2009, 08:39 PM

Hi, I tried posting on a chevy truck forum, but couldn't get any responds. There is a world of knowlege here so excuse me for asking about a non Mercedes question. I have a 1996 K1500 5.7. My son drove the truck the other day and ran out of gas. After he put gas in the truck on the way home from the gas station. The check engine light came on with the code PO171 Low lean on bank #1. I have reset the code a couple of times, but it comes on after driving it for about 20 mins. There was no problem prior to my son running out of gas. What could be causing the code after running out of gas?
Thanks
Mike

pawoSD · #2 04-11-2009, 11:53 PM

From what I could find using google in a quick search, that code is for the Mas Airflow Sensor.

Mike Michalek · #3 04-12-2009, 12:19 AM

Thanks, The tester & the manual I have both state Low Lean Bank #1.

pmckechnie · #4 04-12-2009, 10:14 AM

Are there any other codes. If the only code is p0171 than look for a vacuum leak on the left side of the engine. If the truck is running OK, drive it for a few days and see if it gets any other codes. The P017X codes are some of the hardest to diagnose. Hopefully you will get another code that can help diagnose the problem. Just running out of fuel should not cause a problem like this.
Let us know if you have any more clues.
Paul

Gilly · #5 04-12-2009, 11:36 AM

I wonder if it just got air into that side of the engine (in the fuel rail) and it takes awhile to clear? If it's running OK, other than that code, I'd wait a few more days, then try getting the code cleared.
Gilly

LUVMBDiesels · #6 04-12-2009, 11:46 AM

Run the truck with the fuel cap off for a few minutes. See if that helps. I just changes the MAF on the 'burban. It is an easy five minute R&R, but the part costs around $130.

It could also be the O2 sensor saying that bank is running lean. I just did the four O2 sensors and they were a PITA to get off! There are two pre-cat and two post-cat and of course they are different parts!

Tomguy · #7 04-12-2009, 12:48 PM

I'd suggest to replace both O2 sensors. I've heard of people running out of gas and in the process of trying to restart the engine, or while it's running out and dying, a flame in the manifold burns out the sensor(s). This happened to my boss's Jeep when he tried to restart on ether. If for example the sensor on one bank lost the heater in the sensor, the engine will think that bank is lean.

Mike Michalek · #8 04-12-2009, 08:50 PM

Thanks for the replies. What would running the engine with the gas cap off do? If it was a bad O2 sensor. Wouldn't I get another code. The PO171 code is the only code that I am getting.
Thanks

LUVMBDiesels · #9 04-12-2009, 10:57 PM

The gas cap thing is a trick that usually resets phantom codes. I thin kit has to do with releasing vacuum in the fuel system.

Your truck is like mine and had four O2 sensors two for each bank of cylinders with one before and one after each cat. Replace all four of them (around $250) especially if you have more than 75000 on the truck. The O2 sensors tell the ECU if the engine is running lean or rich. The MAF can maybe be cleaned. Disconnect it and and remove it. Get some MAF cleaner spray (Careful with regular carb cleaner as it could damage the MAF) Spray the crap out of the sensor barrel being careful not to damage the wire. Let it dry and then reinstall.

You can find good info on this forum...
http://www.gmtruckclub.com/forum/

I am jn1965 there...

Gilly · #10 04-13-2009, 04:07 AM

An old saying:
"If you don't know what to do, don't do anything".

Gilly

Two560Two · #11 04-15-2009, 05:04 PM

Quote:

Originally Posted by pmckechnie

Are there any other codes. If the only code is p0171 than look for a vacuum leak on the left side of the engine. If the truck is running OK, drive it for a few days and see if it gets any other codes. The P017X codes are some of the hardest to diagnose. Hopefully you will get another code that can help diagnose the problem. Just running out of fuel should not cause a problem like this.
Let us know if you have any more clues.
Paul

P0171 Lean codes can be somewhat difficult to solve and just changing suspected parts without really doing a proper diag will cost more money and waste time. If you want to start looking for a vacuum leak, get a scanner where you can view your fuel trims, then spray carb cleaner around the suspected areas of a vacuum leak and see if the fuel trims change and note how the engine runs when you spray around suspected areas. If you have exhausted all means of diag yourself, reset the code and try resetting the computer by means of a factory scanner or something similar. Just simply disconnecting the battery wont clear the computers "Keep Alive Memory"

Also, use the scanner to check your O2 readings and check for any other readings that may be out of parameter

PaulC · #12 04-15-2009, 06:57 PM

Quote:

Originally Posted by Gilly

I wonder if it just got air into that side of the engine (in the fuel rail) and it takes awhile to clear? If it's running OK, other than that code, I'd wait a few more days, then try getting the code cleared.
Gilly

I wonder if the fuel rail has a schrader valve that could be used to burp the rail on a COLD engine...

I also wonder if a low fuel pressure situation (dying fuel pump/clogged fuel filter) could trigger the code, even though the code denotes a problem in only one cylinder bank.

t walgamuth · #13 04-15-2009, 07:16 PM

My thinking is along traditional lines. Ran it low maybe got down into some gunk in the tank and plugged the fuel filter.

I did it on my 03 Dodge recently and plugged the filter. (and the filter only had 92K miles on it!)