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Ken, ASE Certified Technician
Category: GM
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Experience:  GM & SATURN Factory Trained Technician, 25 Years Experience
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AUTOZONE CODES WERE PO171 PO174 PO300PO171 PO174

Customer Question

AUTOZONE CODES WERE PO171 PO174 PO300PO171 PO174
Submitted: 5 years ago.
Category: GM
Expert:  Ken replied 5 years ago.
Hi and thanks for your question! First thing I would do is check the fuel pump pressure and filter. The motor is running lean and the computers are adding fuel to keep the motor running. The fuel filter may be plugged or the pump is not building up the the right pressure. I did find a bulletin on those three codes. If the fuel filter and pressure is ok then replace the intake gasket. Thank You Ken
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

 




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

Condition/Concern:

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.

Recommendation/Instructions:

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 5 years ago.

The guy at autozone said he had the same problem with 2002 avalanch and it was the intake gasket. so I bought it but when looking how to put it on it looks very hard. do you have to remove everything that is on top of the mantifold or just the bolts holding it on.

Expert:  Ken replied 5 years ago.

I had to reset my computer, I will be with you in 2 mins. Thank you ken

Expert:  Ken replied 5 years ago.

Intake Manifold Replacement

Removal Procedure

    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.
  2. Remove the fuel injectors.
    Object Number: 679510  Size: SH

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

  7. Object Number: 679527  Size: SH

  8. If equipped, remove the following EGR pipe bolts:
  9. Intake manifold (1)
    Cylinder head (2)
    Exhaust manifold (3)
  10. If equipped, remove the EGR pipe with valve.
  11. If equipped, remove the EGR pipe gasket from the exhaust manifold.

  12. Object Number: 382483  Size: SH

  13. If equipped with vacuum assisted brakes, remove the vacuum brake booster hose from the rear of the intake manifold.

  14. Object Number: 647793  Size: SH

  15. Remove the positive crankcase ventilation (PCV) hose with valve.

  16. Object Number: 260159  Size: SH

  17. Remove the MAP sensor (1) from the intake manifold.

  18. Object Number: 492765  Size: SH

  19. Remove the accelerator control cable bracket bolts (1).
  20. Remove the accelerator control cable bracket (2) from the intake manifold.

  21. Object Number: 372717  Size: SH

  22. Remove the evaporative emission (EVAP) purge solenoid vent tube by performing the following:
  23. 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

  24. Remove the EVAP purge solenoid bolt (2), solenoid (3), and isolator (1) from the intake manifold.

  25. Object Number: 642285  Size: SH

  26. Remove the intake manifold bolts.
  27. Remove the intake manifold.

  28. Object Number: 492770  Size: SH

  29. Remove the intake manifold gaskets (1) from the intake manifold.
  30. Discard the old intake manifold gaskets.
  31. Clean and inspect the intake manifold.
  32. If equipped with EGR, clean the gasket surfaces of the EGR pipe and the exhaust manifold.

Installation Procedure


    Object Number: 492770  Size: SH

  1. Install new intake manifold gaskets (1) to the intake manifold.

  2. Object Number: 642285  Size: SH

  3. Install the intake manifold.
  4. Apply a 5 mm (0.20 in) band of threadlock GM U.S. P/N 12345382, Canada P/N 10953489, or equivalent to the threads of the intake manifold bolts.

  5. Object Number: 63222  Size: SH

    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  6. Install the intake manifold bolts.
    1. Tighten the intake manifold bolts a first pass in sequence to 5 N·m (44 lb in).
    2. Tighten the intake manifold bolts a final pass in sequence to 10 N·m (89 lb in).
  7. Tighten


    Object Number: 389993  Size: SH

  8. Install the EVAP purge solenoid (3), isolator (1), and bolt (2) to the intake manifold.
  9. Tighten
    Tighten the EVAP purge solenoid bolt to 10 N·m (89 lb in).


    Object Number: 372717  Size: SH

  10. Install the EVAP purge solenoid vent tube to the solenoid (1) and vapor pipe.

  11. Object Number: 492765  Size: SH

  12. Install the accelerator control cable bracket (2) to the intake manifold.
  13. Install the accelerator control cable bracket bolts (1).
  14. Tighten
    Tighten the accelerator control cable bracket bolts to 10 N·m (89 lb in).


    Object Number: 260159  Size: SH

    Important: Lightly coat the MAP sensor seal with clean engine oil before installing.

  15. Install the MAP sensor (1) to the intake manifold.

  16. Object Number: 647793  Size: SH

  17. Install the PCV hose with valve.

  18. Object Number: 382483  Size: SH

  19. If equipped with vacuum assisted brakes, install the vacuum brake booster hose to the rear of the intake manifold.

  20. Object Number: 679527  Size: SH

  21. If equipped, position a new EGR pipe gasket on the exhaust manifold.
  22. If equipped, install the EGR pipe with valve.
  23. If equipped, install the following EGR pipe bolts until snug:
  24. Intake manifold (1)
    Cylinder head (2)
    Exhaust manifold (3)
  25. If equipped, tighten the EGR pipe bolts.
  26. Tighten

    Tighten the EGR valve pipe-to-intake manifold bolts to 10 N·m (89 lb in).
    Tighten the EGR valve pipe-to-cylinder head bolts to 50 N·m (37 lb ft).
    Tighten the EGR valve pipe-to-exhaust manifold bolts to 30 N·m (22 lb ft).

  27. Route the electrical harness into position over the engine.

  28. Object Number: 679510  Size: SH

  29. Connect the knock sensor harness electrical connector to the intake manifold.
  30. Connect the following electrical connectors.
  31. MAP sensor (1)
    Knock sensor (2)
    EGR valve, if equipped
  32. Install the fuel injectors.
  33. Install the throttle body.
Expert:  Ken replied 5 years ago.
The most common problem I see with these codes is the fuel pump. I have seen a few plugged fuel filters. You can replace the intake gasket if you want to guess. Ken
Expert:  Ken replied 5 years ago.
Please remember to click " Accepted." Thank You Ken
Ken, ASE Certified Technician
Category: GM
Satisfied Customers: 754
Experience: GM & SATURN Factory Trained Technician, 25 Years Experience
Ken and 2 other GM Specialists are ready to help you
Customer: replied 5 years ago.
thanks for your help ken what do you think i should do first, change the fuel filter? and where is that. or change the fuel pump where is that? or take it to a shop and have a full diog test done on it for about $75. and if i do change one of these and it is the problem will the service engine light go off. changing the manifold gasket looks very time consuming and it is 20 degree outside.
Customer: replied 5 years ago.

And what should the fuel pressure be registering

Expert:  Ken replied 5 years ago.

The fuel filter is on the left frame rail under the truck. I would have that replaced first, then have the fuel pump/ intake gasket checked.

I will try to get the fuel filter replacement information for you in about a hour. The web sight is down for updates. Thank You Ken
Expert:  Ken replied 5 years ago.

Fuel Filter Replacement (Pickup)

Removal Procedure

Important: Inspect the fuel tank internally and clean the fuel tank if you find a restricted fuel filter.


    Object Number: 304085  Size: SH

  1. Relieve the fuel system pressure.
  2. Raise the vehicle.
  3. Clean all the fuel filter connections and the surrounding areas before disconnecting the fuel pipes in order to avoid possible contamination of the fuel system.
  4. Disconnect the threaded fittings (2) from the fuel filter.
  5. Cap the fuel pipes in order to prevent possible fuel system contamination.
  6. Slide the fuel filter from the bracket (1).
  7. Inspect the fuel pipe O-rings for cuts, nicks, swelling, or distortion. Replace the O-rings if necessary.

Installation Procedure


    Object Number: 304085  Size: SH

  1. Slide the fuel filter into the bracket (1).
  2. Remove the caps from the fuel pipes.

    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  3. Connect the threaded fittings (2) to the fuel filter.

    Tighten
    Tighten the fittings to 25 N·m (18 lb ft).

  4. Lower the vehicle.
  5. Tighten the fuel filler cap.
  6. Connect the negative battery cable.
  7. Use the following procedure in order to inspect for leaks:
    7.1. Turn ON the ignition, with the engine OFF, for 2 seconds.
    7.2. Turn OFF the ignition for 10 seconds.
    7.3. Turn ON the ignition, with the engine OFF.
    7.4. Inspect for fuel leaks.
  8. Install the engine sight shield
© 2009 General Motors. All rights reserved.
Customer: replied 5 years ago.
what should the fuel pressure lbs be registering
Expert:  Ken replied 5 years ago.
Key on engine off

(55-62 psi)

engine running, (48-52)

Customer: replied 5 years ago.

Ken just wanted to let you know it was the fuel filter.

Thanks for all your help

Expert:  Ken replied 5 years ago.
Good Job! Please remember to leave some positive feed back. Thank You Ken

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Ken
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GM & SATURN Factory Trained Technician, 25 Years Experience