Engine Code Question

[crbriley]

I have an '02 Silverado with a 5.3 V8. The last two times that I have filled up with gas I get a check your engine light when starting. It goes off after 3-4 starts (apx 30-40 miles?) I had the code tested and it is P0174. What would cause this?

[jrrod2004]

Service Information

 

2002 Chevrolet Chevy C Silverado - 2WD | Sierra, Silverado (VIN C/K) Service Manual | Document ID: 796419 DTC P0171 or P0174

Circuit Description

The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop the PCM determines fuel delivery based on sensor signals, without oxygen sensor input. During Closed Loop, the oxygen sensor inputs are added and used by the PCM to calculate short and long term fuel trim (fuel delivery adjustments). If the oxygen sensors indicate a lean condition, fuel trim values will be above percent. If the oxygen sensors indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain air/fuel ratio of 14.7:1. If the PCM detects an excessively lean condition, this diagnostic trouble code (DTC) will set.

 

Conditions for Running the DTC

 

• DTCs P0101, P0103, P0108, P0135, P0137, P0141, P0200, P0300, P0410, P0420, P0430, P0440, P0442, P0443, P0446, P0449, P0506, P0507 or P1441 are not set.

 

 

• The engine coolant temperature (ECT) is between 75-115°C (167-239°F).

 

 

• The intake air temperature is between -20 to +90°C (4-194°F).

 

 

• The manifold absolute pressure (MAP) is between 26- 90 kPa (3.7-13 psi).

 

 

• The vehicle speed is less than 137 km/h (85 mph).

 

 

• The engine speed is between 400-3,000 RPM.

 

 

• The barometric pressure (BARO) is more than 74 kPa (10.7 psi).

 

 

• The mass airflow (MAF) is between 5-90 g/s.

 

 

• The fuel level is more than 10 percent.

 

 

• The throttle position is less than 90 percent.

 

Conditions for Setting the DTC

 

• The average long term fuel trim cell value is above 23 percent.

 

 

• All of the above conditions are present for 6 seconds.

 

Action Taken When the DTC Sets

 

• The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

 

 

• The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

 

Conditions for Clearing the MIL/DTC

 

• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

 

 

• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

 

 

• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

 

 

• Clear the MIL and the DTC with a scan tool.

 

Diagnostic Aids

 

• The system will go lean if an injector is not suppling enough fuel.

 

 

• A lean condition could be present during high fuel demand.

 

 

• Using scan tool, review Failure Records . If an intermittent condition is suspected, refer to

Intermittent Conditions .

 

Test Description

The numbers below refer to the step numbers on the diagnostic table.

 

 

1. If conditions were not corrected, refer to Fuel System Diagnostics for a possible fuel problem.
   
2. If conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failures may be at fault.
   

Step

 

Action

 

Values

 

Yes

 

No

 

1

 

Did you perform the Diagnostic System Check-Engine Controls?

 

--

 

Go to Step 2

 

Go to Diagnostic System Check - Engine Controls

 

2

 

Important: If any DTCs are set, other than P0171 or P0174, refer to those DTCs before continuing.

 

 

1. Install the scan tool.
   
2. Start and idle the engine at the normal operating temperature in Closed Loop.
   
3. Record the long term fuel trim.
   
4. Turn OFF the engine.
   
5. Turn ON ignition, with engine OFF.
   
6. Review the Freeze Frame/Failure Records and record displayed data for this DTC.
   

Does the scan tool indicate that the Long Term Fuel Trim is greater than the specified value?

 

23%

 

Go to Step 3

 

Go to Diagnostic Aids

 

3

 

 

1. Operate engine at idle.
   
2. Using the scan tool observe HO2S parameters.
   

Does the scan tool indicate that the parameter is within the specified range and fluctuating?

 

200 mv-800 mv

 

Go to Step 4

 

Go to Step 5

 

4

 

 

1. Turn OFF engine.
   
2. Visually and physically inspect the following items:
   

 

• Vacuum hoses for splits, kinks, and proper connections. Refer to

Emission Hose Routing Diagram

 

 

• Ensure that the vehicle has sufficient fuel in tank. If fuel pressure is too low this DTC may set. Refer to

Fuel System Diagnosis

 

 

• Fuel contamination. Refer to

Alcohol/Contaminants-in-Fuel Diagnosis

 

Did you find and correct the condition?

 

--

 

Go to Step 7

 

Go to Step 6

 

5

 

Turn OFF engine and inspect for the following:

 

 

• Check the HO2S for proper installation.

 

 

• Check to ensure electrical connectors and wires are secure and not contacting the exhaust system.

 

 

• Check for a short between the signal circuit and the low reference circuit.

 

Did you find and correct the condition?

 

--

 

Go to Step 7

 

Go to Fuel System Diagnosis

 

<a href="http://gsi.xw.gm.com/si/showDoc.do?docSyskey=796419&pubCellSyskey=28700&pubObjSyskey=796419&from=sm&cellId=28700#TD06">6

 

Operate engine at idle and inspect the following:

 

 

• Check for missing, loose, or leaking exhaust components, forward of the HO2S.

 

 

• Check for vacuum leaks at the intake manifold, throttle body and injector O-rings.

 

 

• Check air induction system and air intake ducts for leaks.

 

 

• Secondary air injection (AIR) system for leaks, improper air delivery, shut-off valve not closing

 

 

• Check crankcase ventilation system for leaks.

 

Did you find and correct the condition?

 

--

 

Go to Step 7

 

Go to Symptoms - Engine Mechanical

 

7

 

Important: After repairs, use scan tool Fuel Trim Reset function in order to reset the Long Term Fuel.

 

 

1. Use a scan tool in order to clear the DTCs.
   
2. Turn OFF the ignition for 30 seconds.
   
3. Start the engine.
   
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
   

Does the DTC run and pass?

 

--

 

Go to Step 8

 

Go to Step 2

 

8

 

With a scan tool, observe the stored information, Capture Info.

 

Does the scan tool display any DTCs that you have not diagnosed?

 

--

 

Go to Diagnostic Trouble Code (DTC) List

 

System OK

 

© 2008 General Motors Corporation. All rights reserved.

[jrrod2004]

Service Information

2002 Chevrolet Chevy C Silverado - 2WD | Sierra, Silverado (VIN C/K) Service Manual | Document ID: 1899786 #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.

 

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.
   

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

 

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

 

 

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

 

 

© 2008 General Motors Corporation. All rights reserved.

[Scramble]

@ M. Cueva or anyone that knows. I threw all three of those codes today. P0171 P0174 P0300 How do you go about testing for the intake leak? And is there any way to get a dealership to do this as warranty work as it's a TSB or am I gonna eat the repair costs?

 

My truck has 68k miles and was wondering if there's any magical law or warranty that would make them do the work.

[silveradocoa]

get a can of carb cleaner, crank the truck and spray around where intake meets head and anywhere else air passes like tb area etc etc. when u find the leak itll start to sputter

[Scramble]

get a can of carb cleaner, crank the truck and spray around where intake meets head and anywhere else air passes like tb area etc etc. when u find the leak itll start to sputter

 

 

Hey, thanks for that info Hummer.....I'll do that. Anyone know if I can make the dealership do the replacement under warranty even if my basic warranty is over?

[Scramble]

Oi guys! Regarding the intake gasket. I saw the corrected part #, but would using something like permatex orange or something similar work? I'm just asking because it'd probably fill more area than a gasket being that these two pieces like to expand and contract at different rates.