Question about 2002 GMC Yukon Denali

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Yukon Denali Fuel Trim bank One and Two running too lean?

SES light is on and the pcm codes of P0171 and P0174 popped up on the OBDII. Replaced the MAF sensor, reset the the PCM and drove it. Sure enough the SES light came back on. Tested and the same two codes pop up. Whats next? 2002 GMC Yukon denali

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  • jaesquibel Dec 22, 2008

    Thanks very much. I checked the two codes on the which tell me that the bank 1 and bank 2 are running too lean, Im a assume to proceed on the fuel side of the system because i just put o2's upstream and reset and sure enough the two codes popped back up. What are the first signs of a pressure regulator going out? or pump? I knw chevys pumps are notorious to go out?

  • terrygabrelc Mar 02, 2009

    I have the same codes for about a year now. I do trouble shooting quite a bit. So I asked myself what changed prior to the problem. I remembered that I put new plugs in right before it started. These have the two electrode tips, where the factory ones had one. Could this cause it to burn the fuel faster causing it to read lean in both banks?

  • Anonymous Mar 24, 2014

    1999 gmc yukon denali starts and runs for approximatly 10 minutes and then stalls could this be the oxygen sensors with the heaters? i do have a code comming up for them

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ARun some good fuel injector cleaner through it. If not that you have vacum leak. Lucas fuel injector cleaner.

Posted on Dec 20, 2012

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Could also be fuel filter, pressure, vacuum leak, etc. Check these two articles out, they should help too - http://www.obd-codes.com/p0171 and http://www.obd-codes.com/p0174

Posted on Dec 21, 2008

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6 Answers

P0171 and p0172 codes


the following links explain the codes and practical and a procedural way of doing so as to not through parts at problem
http://www.obd-codes.com/p0171 http://www.obd-codes.com/p0172

Jul 07, 2016 | 2004 Chevrolet Chevrolet TrailBlazer LS

3 Answers

Code p0171 and p0174


P0171 possible cheap fix

Feb 21, 2015 | 2002 GMC Sierra 1500

1 Answer

P0444


code po444 is referencing a purge control problem. this could be a bad connection or a problem with the purge solenoid for the evaporative system(EVAP). this is controlled by the PCM to allow fuel vapours to be drawn into the engine and burnt from the gas tank under certain conditions. the p0174 is a lean running condition on bank 2 and p0171 is a lean running condition on bank 1. the lean running conditions could be O2 sensors, lean condition caused by bad fuel pressure, dirty injectors, bad MAF sensor, vacuum leak.

Aug 26, 2014 | 2006 BMW 325i

1 Answer

Codes po171 174


Here we go.... just pulled out our service ticket:

Soooo interesting, I had never looked at these before:

So on 1/10/2005 we took the Vue in, and they did the following:
date: 1/10/2005
"CUSTOMER STATES THE SES LIGHT IS ON"
CAUSE: UNKNOWN
TECH COMM: SES LIGHT IS ON. FOUND FUEL TRIM LEAN CODE P0171 & P0174. RETORQUE INTAKE VACUUM CHAMBER BOLTS AND INSTALL VACUUM CHAMBER SPRINGS PER BULLETIN02/06/01/016A

REPAIR 1: INLET AIR CONTROL VACUUM RESERVOIR - REPLACE


Then, evidently it came back on a week later:

date 1/17/2005:

LINE1: "CUSTOMER STATES THE SES LIGHT IS ON"
CAUSE: OPEN
TECH COMM: SES LIGHT IS ON.
FOUND CODE P0171 FUEL TRIM LEAN B1 CODE P0174
FOUDN MASS AIR FLOW SENSOR FAILED REPLACED MAF SENSOR


...

The problem NEVER came back..

There's my experience. Good luck!

Apr 19, 2014 | 2002 Saturn VUE

1 Answer

Ford Taurus Engine Light is: P0171 & P0174. I am thinking a MAF Sensor


Could be a problem with the MAF sensor but if it is you should have a code for that too.
Other causes include low fuel pressure, and a vac leak or air leak in the intake hose to the MAF.
The codes mean the ECM can not make the injectors rich enough to make the O2 sensors switch back and forth.

Jul 29, 2012 | Ford Cars & Trucks

1 Answer

Codes P0171, P0174, and P1401


Hi there:
DTC P0171 & P0174 basically this means that an oxygen sensor in bank 1 has detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1, Bank 2 is generally the side of the engine that doesn't have cylinder #1. Both code is one of the more common trouble codes.



This code is triggered by the first downstream (front) O2 sensor. The sensor provides a reading of the air:fuel ratio leaving the engine's cylinders, and the vehicles powertrain/engine control module (PCM/ECM) uses that reading and adjusts to keep the engine running at that optimum ratio of 14.7:1. If something is not right and the PCM cannot maintain the 14.7:1 ratio, but rather there is too much air, it triggers this code.


You'll want to also read our article on short and long term fuel trims to help understand the operation of the engine. Note: This DTC is very similar to P0174, and in fact your vehicle may show both codes at the same time.


Symptoms
You will more than likely not notice any drivability problems, although there may be symptoms such as:
a lack of power
detonation (spark knock)
rough idle
hesitation/surge on acceleration.


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
Possible cracked vacuum or PCV line/connection
Faulty or stuck open PCV valve
Failed or faulty oxygen sensor (bank 1, sensor 1)
Sticking/plugged or failed fuel injector
Low fuel pressure (possible plugged/dirty fuel filter!)
Exhaust leak between engine and first oxygen sensor


Possible Solutions: a lot of times, cleaning the MAF sensor and finding/fixing vacuum leaks fix the problem. If you're on a tight budget, start there, but that may not be the fix for certain. So, possible solutions include:


Clean the MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
Inspect all vacuum and PCV hoses, replace/repair as required
Inspect all hoses and connections in the air intake system
Inspect and/or test the intake manifold gaskets for leakage
Check for a dirty fuel filter and proper fuel pressure
Ideally you'll want to monitor short and long term fuel trims using an advanced scan tool
If you have access, you may want to run a smoke test




DTC P1401 Diff Pres Feedback EGR Circ High Input
Disconnected and plugged vacuum line from EGR valve. Truck ran better.
Put length of hose on EGR valve, turned up 2000 RPM and applied small amount of vacuum (by mouth) and engine started to stall. This would seem to indicate that the EGR valve is working and passages are clear.
Truck seems to run just a little rough. Cleared trouble code


Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Jul 17, 2012 | Ford Windstar Cars & Trucks

1 Answer

Code 171 bank 1 system running to lean?


Hi there:
DTC P0171 - System Too Lean (Bank 1)
Basically this means that an oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1.

Note: This DTC is very similar to P0174, and in fact your vehicle may show both codes at the same time.

You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.

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.

Possible solutions include:
In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
Inspect all vacuum and PCV hoses, replace if necessary
Check for a dirty fuel filter and proper fuel pressure


On rare occasions, a check engine light may be experienced with DTC P0171, P0441, P0455, and/or P2420. These DTCs may be a result of an internal PCM driver issue that may keep the EVAP purge solenoid control circuit grounded at times instead of supplying a pulse width signal on the circuit. ask your dealer and check this TSB:
#PIP3621: DTCs P0171, P0441, and/or P2420 - Inspect Production Part Number on PCM - keywords CEL check ECM EVAP lamp lean light repeat trim updated - (Nov 9, 2005)
Subject: DTCs P0171, P0441, P0455 and/or P2420 - Inspect Production Part Number on PCM

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Feb 29, 2012 | Cars & Trucks

4 Answers

Check Engine light is on my 1997 F150 with a small V-8. The tester returns codes P0171, P0172, P0174 and P0175. What does all this mean?


those codes are for lean engine condition look for vac leaks at the back of engine to the pcv valve could hear hissing noise with engine running also check egr valve to be stuck open also when was last fuel filter changed? hope this helps .

Sep 16, 2009 | 1997 Ford F150 Regular Cab

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