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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1 Answer

Vehicle CEL is on, various codes


P0300 is a random miss fire , a vacuum leak can cause this as well as low fuel pressure ! weak fuel pump , clogged fuel filter !
DTC P0171: Fuel Trim System Lean Bank 1
DTC P0174: Fuel Trim System Lean Bank 2 These two codes are saying the PCM - engine computer is see a lean condition .
DTC P0191: Fuel Rail Pressure (FRP) Sensor Performance
Circuit/System Description
The fuel pressure sensor is located on the fuel line. The fuel pressure sensor monitors the fuel pressure in the fuel line. The fuel pump flow control module (FPCM) monitors the voltage signal from the fuel pressure sensor.

You don't say what make , model an year vehicle ! These are for GM vehicles , yours could mean something else . Except the first three , those are genaric codes , same for all makes ! So can't say what this codes are P2097, and P2099 ! Can't mean this P2097 - Post Catalyst Fuel Trim System Too Rich Bank 1
P2099 - Post Catalyst Fuel Trim System Too Rich Bank 2

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Code p0171 and p0174


P0171 possible cheap fix

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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.

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P0171 - Fuel Trim System Lean Bank 1 and/or DTC P0174 - Fuel Trim System Lean Bank 2


DTC P0171 probable cause:
1. Wire harness problem. Check for correct voltage, opne, short toground, short to voltage
2. Fuel pressure problem. Check pump, regulator, filter and lines
3. Exhaust leaks or restrictions
4. Vacuum hoses. Leaks or incorrect routing
5. Contaminated fuel
6. Sensor improperly installed

DTC P0174 probable cause:
1. Faulty sensor or solenoid
2. Damaged or corroded connector terminal contact
3. Wire harness problem. Check for correct voltage, open, short to ground, short to voltage
4. Control unit software in need of update
5. Faulty PCM or ECM
6. Lean fuel mixture
7. Fuel pressure problem. Check pump, regulator, filter, and lines

Jun 08, 2014 | 2003 Saturn VUE

1 Answer

What is p0171 p0174?


P0171 Fuel trim bank one condition Lean (If bank one and two codes set together suspect fuel pressure or MAF sensor. Or O2 sensor defective
P0174Fuel trim bank two condition Lean (same as above or Failed H02S21 Heated O2 sensor Bank 2 sensor 1)

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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!

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1 Answer

4 Codes in computer


code p0128 indicates a mechanical fault ( could be the thermostat stuck open)
code p0174 -system too lean -bank2 ===causes --intake /exhaust leak--fuel pressure/pump--injectors--AIR system--hose connection/s
code po171 refers to system too lean bank 1 same as po174 with the HO2S sensor being the culprit. As to all being related . only by way of the o2 sensors
code p0442 is not connected to the first 3 as it is in a different section of the fuel system

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1 Answer

Engine light on


P0171 ; Fuel Trim System Lean (Bank 1)
P0174; Fuel Trim too Lean (Bank 2)
fuel trim is system to modify injector pulse if system go lean it will go rich when the system is too much lean and is max.rich it code
look for 02 sensor bank 1 and 2 data
hope it helps

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1 Answer

My engine light is on and the codes are reading system to lean bank 1 and 2. The code are p0171 and p0174


This is sign of a vacuum leak (possible off of the PCV system). This causes additional air to be introduced into the engine causing the fuel mixture to lean out. With the engine running, shoot short burst of starting fluid around the vacuum lines. When the engine revs briefly, you have found (at least one of) your leaks.

Jan 07, 2011 | 2003 GMC Yukon Denali

1 Answer

What are these codes and how do I fix them? P0101 P0171 P0174


  • P0101 - Mass Air Flow (MAF) Sensor Performance
  • P0171 - Fuel Trim System Lean Bank 1
  • P0174 - Fuel Trim System Lean Bank 2
  • Would start with the mass air flow sensor the other two codes may have been triggered by the performance of the MAF sensor. Is the vehicle running poorly or have high or low idle?

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