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2003 Chevy Suburban Codes P0170 & P0171

Tiny
HANKO3RD
  • MEMBER
  • 2003 CHEVROLET SUBURBAN
Computer problem
2003 Chevy Suburban V8 Four Wheel Drive 56,000 miles

Check engine light came on in 2003 Suburban, had Auto Zone run a Check and returned Codes P0170 and P0171. They recommended O2 Sensors. Looking around there seems to be some disagreement on this as a solution for these codes together. Majority point to dirty MAF Sensor and suggest cleaning that. Any recommendations here on the best course of resolving this?

Thanks,
Hank
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Wednesday, November 19th, 2008 AT 12:17 AM

11 Replies

Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
I don't believe the 02 sensor is your problem.

A code P0171 may mean that one or more of the following has happened:

The MAF (Mass Air Flow) Sensor is dirty or faulty.

Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.

There could be a vacuum leak downstream of the MAF sensor.

I suggest doing the following before replacing anything.
In the vast majority of cases, simply cleaning the MAF sensor does the trick. If you need instructions on doing this, just let me know and I will post them here for you.
Inspect all vacuum and PCV hoses, replace if necessary
Check for a dirty fuel filter and proper fuel pressure.
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Wednesday, November 19th, 2008 AT 12:44 AM
Tiny
HANKO3RD
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Thank you. Yes, please post the instructions for cleaning the MAF sensor. Also, how do I check for a dirty fuel filter? For fuel pressure I assume I'd get a fuel pressure guage. Thanks again for your guidance.

Hank
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Wednesday, November 19th, 2008 AT 4:11 AM
Tiny
BLUELIGHTNIN6
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First, remove the MAF sensor from the vehicle. The MAF sensor should always be located in the air duct between the air filter and the throttle body.

Picture of MAF sensor connector location (1) and flow direction (2) for 2000-2005 4.8L, 5.3L, 6.0L engines below.


https://www.2carpros.com/forum/automotive_pictures/261618_0900c152800a6a9e_1.jpg



NOTE: DO NOT USE CARBURATOR CLEANER!

To clean, spray some electrical contact cleaner (something that leaves NO residue) through the sampling tube over the wires. I recommend using a MASS AIR FLOW cleaner from your local auto parts store. It is specially made for this job and only costs a few dollars.

Start with this first, post your results and if it doesn't help your issue then we will go on to the fuel filter.

I think this will do it for you though.

Thanks for using 2carpros.com!
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Wednesday, November 19th, 2008 AT 12:55 PM
Tiny
HANKO3RD
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Thanks. I'll do this tonight and see if it makes a difference. I'll let you know the results. Offhand do you know when the check engine light will reset if this is the solution?

-Hank
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Wednesday, November 19th, 2008 AT 6:08 PM
Tiny
BLUELIGHTNIN6
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In most cases, you will have to disconnect the battery for 10 minutes and reconnect it to reset the engine light. You can also have AutoZone delete the code the same way they ran the diagnostic scan for you. It should stay out, if it comes on again then you need to have it scanned at AutoZone again to see if it is same codes.
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Thursday, November 20th, 2008 AT 12:08 AM
Tiny
HANKO3RD
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I cleaned the MAF Sensor and replaced the air filer at the same time. There was a slight improvement, however, when idling it "lopes" between 4,000 and 6,000 rpm-not dying but sounding close. Oddly when it drops to the 4,000 rpm mark the lights dim. The check engine light is still on, I was negligent (read as lazy) and haven't cleared the codes, so I cant offer anything there.

Thanks,
Hank
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Friday, November 21st, 2008 AT 9:33 PM
Tiny
BLUELIGHTNIN6
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Was it idleing incorrectly when you first posted? Because you neglected to state that, if so.

I suggest having the codes erased and read again in order for me to better assist you.
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Friday, November 21st, 2008 AT 9:46 PM
Tiny
OYSIFLY
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Ok, This is the exact same problem that I have been having for 3 years! It runs GREAT in the summer when it is warm out, but when temps drop to cold ( around 40 deg) I get a really rough idle and sometimes will die. I got the exact same codes from Auto Zone so I bought a MAF and NOTHING changed. I have taken it to 3 places and noone can figure this out. When the temps go back up the rough idle stops and it runs like a champ. This has us so stumped it is not even funny. Super annoying when it dies dropping the kids off in the school line. ANY help in this matter would be great. Thanks.
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Wednesday, December 3rd, 2008 AT 9:47 PM
Tiny
RBURTON21
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Okay, I have the same issue.I replaced teh MAF Sensor and seemed to make a slight difference in performance. But I am still having the same problem. Here are my symptoms:

1. Prior to replacing the MAF Sensor, the idle did flex between 4k and 6k. It did die once and the outside temp was very cold (25 degrees).

2. After one day of smooth performace the check engine light came back but the idle seems okay.

3. I added some injector cleaner as well, the PO171 code indicated possible fuel injector problem as well.

Autozone also said that the problem could be a result of a faulty cooling system sensor?

Any help would be really appreciated.

Ryan
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Tuesday, December 23rd, 2008 AT 3:55 PM
Tiny
BLUELIGHTNIN6
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If your engine is idling up and down like that then I would suspect a faulty IAC valve (Idle Air Control Valve). Located on throttle body.
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Wednesday, December 24th, 2008 AT 12:27 AM
Tiny
AZ_ADOBE
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I followed the advice on using MAS cleaner. Sprayed it on a few times - saw the sensor wires change from black to silver. Clear the codes and have been driving it for a couple days with no re-appearance of the codes.
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Sunday, January 10th, 2010 AT 9:24 PM

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