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John, Master A.S.E Automotive technician
Category: Chevy
Satisfied Customers: 9176
Experience:  A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician
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2002 Yukon XL 1500: Have codes p300, P0171 and P0174..hesitation

Customer Question

I have 2002 Yukon XL 1500. Have codes P0300, P0171 and P0174 and have also seen P0172. At idle there is hesitation, dropping out when cold.
Submitted: 7 years ago.
Category: Chevy
Expert:  John replied 7 years ago.


This is a pretty common problem & I am sending info to repair your problem.

PIP3232B: Cold Engine Idle Misfire Or DTCs P0171 P0174 - keywords 4.8 5.3 6.0 air cold crack hesitate idle intermittent internal intake leak lean misfire miss P0171 P0174 P0300 power rough surge vacuum - (Feb 7, 2007)

Subject:Cold Engine Idle Misfire or DTCs P0171 P0174

Models:2002-2005 Cadillac Escalade
1999-2005 Chevrolet Avalanche, Express, Silverado, Suburban, Tahoe, Trailblazer
1999-2005 GMC Savana, Sierra, Yukon
2003-2005 Hummer H2


This PI was superseded to update parts information. Please discard PIP3232A.


The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

99 through 05 GEN III truck engines may experience any of the following:

  1. A cold rough idle that diminishes as the engine warms up.
  2. Possible DTCS P0171, P0174, or P0300.
  3. Random misfires at idle.

The intake gasket seals may be leaking around the intake ports, causing a lean condition. The intake gasket seals may leak around the bottom side of the port, making it a challenge to detect the vacuum leak. The technician may also notice lower than normal MAF readings if the intake seals are leaking.

  1. If leaking intake gasket seals are found, replace the intake gaskets. During the repair be sure to use the current GMSPO part number for replacement intake gaskets. The current GMSPO part number for intake gaskets will have a teal green intake gasket seal. The old version of the intake gaskets were orange in color. Use only the teal green colored gaskets for a repair.
  2. The intake plenum should also be checked for excessive warpage that may cause an uneven clamping pressure of the seal. If the plenum is found to be warped it will need to be replaced. Service Information states, "An intake manifold with warpage in excess of 3 mm (0.118 in) over a 200 mm (7.87 in) area should be replaced". Intake warpage is measured at the gasket sealing surfaces, and should be measured within a 200 mm (7.87 in) area. This measurement is across only two of the intake runner port openings. Measurements taken across the entire distance of all four intake runner ports will lead to unnecessary manifold replacements.
Customer: replied 7 years ago.
Is there a procedure/instructions for replacing the intake gaskets?
Expert:  John replied 7 years ago.

Yes ,this should help.

Intake Manifold Replacement

    Important: The intake manifold, throttle body, fuel rail, and injectors may be removed as an assembly. If not servicing the individual components, remove the manifold as a complete assembly.

  1. Remove the throttle body. Remove the fuel injectors. Object Number: 679510  Size: SH

  2. Disconnect the following electrical connectors:
    Manifold absolute pressure (MAP) sensor (1)
    Knock sensor (2)
    Exhaust gas recirculation (EGR) valve, if equipped.
  3. Remove the knock sensor harness electrical connector from the intake manifold.
  4. Set the electrical harness aside.
    Object Number: 679527  Size: SH

  5. If equipped, remove the following EGR pipe bolts:
    Intake manifold (1)
    Cylinder head (2)
    Exhaust manifold (3)
  6. If equipped, remove the EGR pipe with valve.
  7. If equipped, remove the EGR pipe gasket from the exhaust manifold.
    Object Number: 382483  Size: SH

  8. If equipped with vacuum assisted brakes, remove the vacuum brake booster hose from the rear of the intake manifold.
    Object Number: 647793  Size: SH

  9. Remove the positive crankcase ventilation (PCV) hose with valve.
    Object Number: 260159  Size: SH

  10. Remove the MAP sensor (1) from the intake manifold.
    Object Number: 492765  Size: SH

  11. Remove the accelerator control cable bracket bolts (1).
  12. Remove the accelerator control cable bracket (2) from the intake manifold.
    Object Number: 372717  Size: SH

  13. Remove the evaporative emission (EVAP) purge solenoid vent tube by performing the following:
    14.1. Remove the EVAP tube end (2) from the solenoid (1).
    14.2. Squeeze the EVAP pipe quick connect fitting (3) retainer together.
    14.3. Remove the EVAP tube end (3) from the vapor pipe.

    Object Number: 389993  Size: SH

  14. Remove the EVAP purge solenoid bolt (2), solenoid (3), and isolator (1) from the intake manifold.
    Object Number: 642285  Size: SH

  15. Remove the intake manifold bolts.
  16. Remove the intake manifold.
    Object Number: 492770  Size: SH

  17. Remove the intake manifold gaskets (1) from the intake manifold.
  18. Discard the old intake manifold gaskets.
  19. Clean and inspect the intake manifold. If equipped with EGR, clean the gasket surfaces of the EGR pipe and the exhaust manifold.
Customer: replied 7 years ago.
when you replace the gaskets should you use any gasket adhesive or other compound? Is there another gasket needed for the EGR?
Expert:  John replied 7 years ago.
Do not use sealer these are special gaskets & the EGR gasket comes in an intake set from GM.
Customer: replied 7 years ago.
what are the chances that the egr valve is bad? If I accept the answer will I still be able to ask a follow up question if necessary?
Expert:  John replied 7 years ago.
I do not believe your EGR valve is bad,it will not set all these codes.Yes .you accept the answer & come back anytime.
John and 7 other Chevy Specialists are ready to help you
Customer: replied 7 years ago.
Thanks for the information, now I have to decide if I want to do it myself!
Expert:  John replied 7 years ago.
Ok,you have a good day.
Customer: replied 7 years ago.
Do you have any information on how to disconnect the fule lines from the fuel rails on the intake manifold? I removed the clips but don't know how to get the connector apart.
Expert:  John replied 7 years ago.

This should help you.You will need a special tool that most parts suppliers keep in stock.

Metal Collar Quick Connect Fitting Service

Tool Required

Fuel Line Disconnect Tool

Removal Procedure

  1. Relieve the fuel system pressure before servicing any fuel system connection. Remove the retainer from the quick-connect fitting.
    Object Number: 12776  Size: SH

  2. Caution: Wear safety glasses when using compressed air in order to prevent eye injury.

  3. Blow dirt out of the fitting using compressed air.
    Object Number: 12780  Size: SH

  4. Choose the correct tool from the tool set for the size of the fitting. Insert the tool into the female connector, then push inward in order to release the locking tabs.
    Object Number: 12782  Size: SH

  5. Pull the connection apart.

    Notice: If necessary, remove rust or burrs from the fuel pipes with an emery cloth. Use a radial motion with the fuel pipe end in order to prevent damage to the O-ring sealing surface. Use a clean shop towel in order to wipe off the male tube ends. Inspect all the connections for dirt and burrs. Clean or replace the components and assemblies as required.

  6. Use a clean shop towel in order to wipe off the male pipe end.
  7. Inspect both ends of the fitting for dirt and burrs. Clean or replace the components as required.

Installation Procedure

    Object Number: 12784  Size: SH

    Caution: Always apply a few drops of clean engine oil to the male pipe ends before connecting the fuel pipe fittings in order to reduce the risk of fire and personal injury. This will ensure proper reconnection and prevent a possible fuel leak. During normal operation, the O-rings located in the female connector will swell and may prevent proper reconnection if not lubricated.

  1. Apply a few drops of clean engine oil to the male pipe end.
    Object Number: 12786  Size: SH

  2. Push both sides of the fitting together in order to snap the retaining tabs into place.
    Object Number: 12787  Size: SH

  3. Once installed, pull on both sides of the fitting in order to make sure the connection is secure.
  4. Install the retainer to the quick-connect fitting.

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