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- - Trouble code (http://www.elcovaforums.com/forums/showthread.php?t=10458)

Today my check engine light came on so I checked the code and it read a PO171 and a PO174 ....which to my reference is something about a lean condition. Has anyone else seen these codes before or have any reference to them?
Thanks.

(Been reading the forums for about a year, but never really post...thanks for all the tips and advice from all the great members here!)

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Document ID# 743995

2003 HUMMER H2

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<H1>DTC P0171 or P0174</H1>

<A NAME="ss1-743995">
<A HREF="#ss1-743995">
<H5>Circuit Description</A></H5>

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 (O2S) input. During Closed Loop, the O2S inputs are added and used by
the PCM to calculate short and long term fuel trim fuel delivery adjustments. If the
O2S indicate a lean condition, fuel trim values will be above 0percent. If
the O2S indicate a rich condition, fuel trim values will be below 0percent.
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
an air/fuel ratio of 14.7:1. If the PCM detects an excessively lean condition, DTC
P0171 or P0174 sets.</P>

<A NAME="ss2-743995">
<A HREF="#ss2-743995">
<H5>Conditions for Running the DTC</A></H5>
<UL TYPE="BULLET">
<LI>DTCsP0101, P0103, P0108, P0135, P0137, P0141, P0200, P0300, P0410,
P0420, P0430, P0440, P0442, P0443, P0446, P0449, P0506, P0507 or P1441 are not set.
</LI>

<LI>The engine coolant temperature (ECT) is between 75-115°C (167-239°F).
</LI>

<LI>The intake air temperature (IAT) is between -20 to +90°C (4-194°F).
</LI>

<LI>The manifold absolute pressure (MAP) is between 26-90kPa
(3.7-13psi).
</LI>

<LI>The vehicle speed is less than 137km/h (85mph).
</LI>

<LI>The engine speed is between 400-3,000RPM.
</LI>

<LI>The barometric pressure (BARO) is more than 74kPa (10.7psi).
</LI>

<LI>The mass airflow (MAF) is between 5-90g/s.
</LI>

<LI>The fuel level is more than 10percent.
</LI>

<LI>The throttle position (TP) is less than 90percent.
</LI>[/list]

.</P>

<A NAME="ss3-743995">
<A HREF="#ss3-743995">
<H5>Conditions for Setting the DTC</A></H5>
<UL TYPE="BULLET">
<LI>The average long term fuel trim cell value is above 23percent.
</LI>

<LI>All of the above conditions are present for 6seconds.
</LI>[/list]

<A NAME="ss1-727820">
<A HREF="#ss1-727820">
<H5>Action Taken When the DTC Sets</A></H5>
<UL TYPE="BULLET">
<LI>The control module illuminates the malfunction indicator lamp

(MIL) on the second consecutive ignition cycle that the diagnostic runs and

fails.
</LI>

<LI>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.
</LI>[/list]

<A NAME="ss1-727824">
<A HREF="#ss1-727824">
<H5>Conditions for Clearing the MIL/DTC</A></H5>
<UL TYPE="BULLET">
<LI>The control module turns OFF the malfunction indicator lamp (MIL)
after 3consecutive ignition cycles that the diagnostic runs and does
not fail.
</LI>

<LI>A current DTC, Last Test Failed, clears when the diagnostic runs
and passes.
</LI>

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

<LI>Clear the MIL and the DTC with a scan tool.
</LI>[/list]

<A NAME="ss4-743995">
<A HREF="#ss4-743995">
<H5>Diagnostic Aids</A></H5>
<UL TYPE="BULLET">
<LI>The system will go lean if an injector is not suppling enough fuel.
</LI>

<LI>A lean condition could be present during high fuel demand.
</LI>

<LI>Use a scan tool in order to review the Failure Records . If an intermittent
condition is suspected, refer to
Intermittent Conditions
.
</LI>[/list]
<A NAME="ss5-743995">
<A HREF="#ss5-743995">
<H5>Test Description</A></H5>

The numbers below refer to the step numbers on the diagnostic table.</P>

<A NAME="TD05">
<LI VALUE=5>

If conditions were not corrected, refer to Fuel
System Diagnosis for a possible fuel problem.</P>
</LI><A NAME="TD06">
<LI VALUE=6>

If conditions were not corrected, a worn cam, worn
intake or exhaust valves, or other engine mechanical failure may be the problem.</P>
</LI>

<TABLE WIDTH="100%" BORDER=1>
<TR>
<TH ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Step</P>
</TH><TH ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Action</P>
</TH><TH ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Values</P>
</TH><TH ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Yes</P>
</TH><TH ALIGN="center" VALIGN="bottom" ROWSPAN=1>

No</P>
</TH></TR>
<TR>
<TD ALIGN="center" VALIGN="middle" ROWSPAN=1><A NAME="S01">

1</P>
</A></TD><TD ALIGN="left" VALIGN="top" ROWSPAN=1>

Did you perform the Diagnostic System Check-Engine Controls?</P>
</TD><TD ALIGN="center" VALIGN="middle" ROWSPAN=1>

--</P>
</TD><TD ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Go to
Step2

</P>
</TD><TD ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Go to
Diagnostic System Check - Engine Controls </P>
</TD></TR>
<TR>
<TD ALIGN="center" VALIGN="middle" ROWSPAN=1><A NAME="S02">

2</P>
</A></TD><TD ALIGN="left" VALIGN="top" ROWSPAN=1>

<FONT COLOR=brown>
<H4>Important</H4>

If any DTCs other than P0171 or P0174 are
set, refer to those DTCs before continuing</P>
</FONT></P>

<LI TYPE="1">Install the scan tool.</LI>
<LI TYPE="1">Start and idle the engine at the normal operating temperature in Closed
Loop.</LI>
<LI TYPE="1">Record the long term fuel trim.</LI>
<LI TYPE="1">Turn OFF the engine.</LI>
<LI TYPE="1">Turn ON ignition, with engine OFF.</LI>
<LI TYPE="1">Review the Freeze Frame/Failure Records and record the displayed data
for this DTC.</LI>

Does the scan tool indicate that the long term fuel trim is greater than the
specified value?</P>
</TD><TD ALIGN="center" VALIGN="middle" ROWSPAN=1>

23% </P>
</TD><TD ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Go to
Step3

</P>
</TD><TD ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Go to Diagnostic Aids </P>
</TD></TR>
<TR>
<TD ALIGN="center" VALIGN="middle" ROWSPAN=1><A NAME="S03">

3</P>
</A></TD><TD ALIGN="left" VALIGN="top" ROWSPAN=1>

<LI TYPE="1">Operate engine at idle.</LI>
<LI TYPE="1">Observe the HO2S parameters with a scan tool.</LI>

Does the scan tool indicate that the parameter is within the specified range
and fluctuating?</P>
</TD><TD ALIGN="center" VALIGN="middle" ROWSPAN=1>

200-800mV</P>
</TD><TD ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Go to
Step4

</P>
</TD><TD ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Go to
Step5

</P>
</TD></TR>
<TR>
<TD ALIGN="center" VALIGN="middle" ROWSPAN=1><A NAME="S04">

4</P>
</A></TD><TD ALIGN="left" VALIGN="top" ROWSPAN=1>

<LI TYPE="1">Turn OFF the engine.</LI>
<LI TYPE="1">Visually and physically inspect the following items:</LI>

<UL TYPE="BULLET">
<LI>The vacuum hoses for splits, kinks, and proper connections. Refer to.
Emission Hose Routing Diagram

</LI>

<LI>Ensure that the vehicle has sufficient fuel in tank. If fuel pressure
is too low this DTC may set. Refer to.
Fuel System Diagnosis
</LI>

<LI>Fuel contamination--Refer to
Alcohol/Contaminants-in-Fuel Diagnosis
</LI>

[/list]

Did you find and correct the condition?</P>
</TD><TD ALIGN="center" VALIGN="middle" ROWSPAN=1>

--</P>
</TD><TD ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Go to
Step7

</P>
</TD><TD ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Go to
Step6

</P>
</TD></TR>
<TR>
<TD ALIGN="center" VALIGN="middle" ROWSPAN=1><A NAME="S05">

5

</P>
</A></TD><TD ALIGN="left" VALIGN="top" ROWSPAN=1>

<LI TYPE="1">Turn OFF the engine.</LI>
<LI TYPE="1">Inspect the HO2S for proper installation.</LI>
<LI TYPE="1">Verify the electrical connectors and the wires are secure, and not contacting
the exhaust system.</LI>
<LI TYPE="1">Test for continuity between the HO2S signal circuit and the low reference
circuit. Refer to
Circuit Testing
and
Wiring Repairs
in Wiring Systems.</LI>

<LI TYPE="1">Operate the engine at idle.</LI>
<LI TYPE="1">Inspect for any missing, loose, or leaking exhaust components forward
of the HO2S.</LI>
<LI TYPE="1">Inspect for vacuum leaks at the intake manifold, throttle body, and injector
O-rings.</LI>
<LI TYPE="1">Inspect the air induction system and the air intake ducts for leaks.</LI>
<LI TYPE="1">Inspect the secondary air injection (AIR) system for leaks, improper air
delivery, and for the shut-off valves not closing.</LI>
<LI TYPE="1">Inspect the crankcase ventilation system for leaks. Refer to
Crankcase Ventilation System Inspection/Diagnosis
in Engine
Mechanical.</LI>

Did you find and correct the condition?</P>
</TD><TD ALIGN="center" VALIGN="middle" ROWSPAN=1>

--</P>
</TD><TD ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Go to
Step7

</P>
</TD><TD ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Go to
Symptoms - Engine Mechanical
in
Engine Mechanical</P>
</TD></TR>
<TR>
<TD ALIGN="center" VALIGN="middle" ROWSPAN=1><A NAME="S07">

7</P>
</A></TD><TD ALIGN="left" VALIGN="top" ROWSPAN=1>

<FONT COLOR=brown>
<H4>Important</H4>

After repairs, use the scan tool Fuel Trim
Reset function in order to reset the Long Term Fuel Trim.</P>
</FONT></P>

<LI TYPE="1">Clear the DTCs with a scan tool.</LI>
<LI TYPE="1">Turn OFF the ignition for 30seconds.</LI>
<LI TYPE="1">Start the engine.</LI>
<LI TYPE="1">Operate the vehicle within the Conditions for Running the DTC. You may
also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure
Records.</LI>

Did the DTC fail this ignition?</P>
</TD><TD ALIGN="center" VALIGN="middle" ROWSPAN=1>

--</P>
</TD><TD ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Go to
Step2

</P>
</TD><TD ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Go to
Step8

</P>
</TD></TR>
<TR>
<TD ALIGN="center" VALIGN="middle" ROWSPAN=1><A NAME="S08">

8</P>
</A></TD><TD ALIGN="left" VALIGN="top" ROWSPAN=1>

Observe the Capture Info with a scan tool.</P>

Are there any DTCs that have not been diagnosed?</P>
</TD><TD ALIGN="center" VALIGN="middle" ROWSPAN=1>

--</P>
</TD><TD ALIGN="center" VALIGN="bottom" ROWSPAN=1>

Go to
Diagnostic Trouble Code (DTC) List </P>
</TD><TD ALIGN="center" VALIGN="bottom" ROWSPAN=1>

System OK</P>
</TD></TR>
</TABLE>

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2003 HUMMER H2

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<LI TYPE="1">Perform a fuel injector balance test for all 8 cylinders. If a fuel injector

concern exists, it is possible to misfuel an entire bank of the engine, causing multiple

cylinders on the same bank to misfire even though the root cause is a single fuel

injector. </LI>
<LI TYPE="1"> Inspect O2 sensor connections on the misfiring bank for corrosion or

water intrusion. If water intrusion is found on the right bank, it may be due to the

AC Evaporator Condensation dripping onto the O2 sensor harness. If this condition

is found, reposition and shield the harness to prevent a repeat concern and repair

the connections.</LI>
<LI TYPE="1">Check for excessive exhaust backpressure using the restricted exhaust

diagnosis from SI.</LI>
<LI TYPE="1">Swap the Position 1 O2 sensors side to side to see if the misfires move

to the other bank of the engine. If so, replace the O2 sensor.</LI>

.</P>

Please follow this diagnosis 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. If these steps do not resolve the condition, please contact

GM TAC for further diagnostic assistance.</P>

<A NAME="ss3-1537547">
<A HREF="#ss3-1537547">
<H5>Models:</A></H5>

(00 - 05 Cadillac Escalade - C6 and K6) and (02 - 05 Chevrolet Avalanche -

C1, C2 K1 and K2) and (99 - 05 Chevrolet Silverado - C1, C2 K1 and K2) and (00 -

05 Chevrolet Suburban - C1, C2, K1 and K2) and (00 - 05 Chevrolet Tahoe - C1 and

K1) and (99 - 05 GMC Sierra C1, C2 K1 and K2) and (00 - 05 GMC Yukon - C1, C2, K1

and K2) and (03 - 05 Chevrolet Express G1, G2, G3, H1, H2 ) and (03 - 05 GMC Savana

G1, G2, G3, H1, H2 ) and (04 - 05 Buick Rainier S1, T1 ) and (03 - 05 Chevrolet Trail

Blazer EXT S1, T1 ) and (03 - 05 GMC Envoy XL XUV S1, T1 ) and (03 - 05 Hummer H2)

and (04 - 05 Cadillac CTS-V DB) and (98 - 02 Chevrolet Camaro FB) and (97 - 04 Chevrolet

Corvette YB) and (98 - 02 Pontiac Firebird FB) and (04 - 05 Pontiac GTO VB) </P>

.</P>

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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.

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2003 HUMMER H2

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<TD align=middle width="50%">Document ID# 1565073
2003 HUMMER
H2 </TD>
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<H1>99-03 GEN III Engine Misfire at Idle Cold and Possible P0171 and/or P0174
-kw 4.8 5.3 6.0 LR4 LM4 LM7 LQ4 crack air hesitate intermittent internal intake
leak lean miss power rough surge vacuum P0300 #PIP3232 - (Nov 15,
2004)</H1>99-03 GEN III Engine Misfire at Idle Cold and Possible P0171 and/or
P0174

.</P>

The following diagnosis might be helpful if the vehicle exhibits the symptom
described in the PI.</P><A name=ss1-1565073><A
href="http://204.89.220.10:9001/servlets/BlobShtml?ShtmlFile=1565073&psdid=293&evc= sm#ss1-1565073">
<H5>Condition/Concern:</A></H5>

99 through 03 GEN III truck engines may experience any of the following: </P>

<LI type=1>A cold rough idle that diminishes as the engine warms up.
<LI type=1>Possible DTCs P0171, P0174, or P0300.
<LI type=1>Random misfires at idle. </LI>

<A name=ss2-1565073><A
href="http://204.89.220.10:9001/servlets/BlobShtml?ShtmlFile=1565073&psdid=293&evc= sm#ss2-1565073">
<H5>Recommendation/Instructions:</A></H5>

Check for leaking intake manifold seals around the intake ports. The intake
gasket seals may be leaking around the intake ports, causing a lean condition.
Many times they will leak around the bottom side of the port, making it a
challenge to detect the vacuum leak. The technician may also note lower than
normal MAF readings if the seals are leaking around the ports. If leaking intake
gasket seals are found, they should be replaced. The intake plenum should also
be checked for 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 with new seals.
Intake Manifold Cylinder Head Deck Flatness specifications are located in SI.
</P>

.</P>

Please follow this diagnosis 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. If these steps do not resolve the condition,
please contact GM TAC for further diagnostic assistance.</P><A
name=ss3-1565073><A
href="http://204.89.220.10:9001/servlets/BlobShtml?ShtmlFile=1565073&psdid=293&evc= sm#ss3-1565073">
<H5>Models:</A></H5>

(99 00 01 02 03 C1 C2 C3 K1 K2 K3 LR4 LM4 LM7 LQ4 LQ9 Chevrolet Silverado
Tahoe Suburban Avalanche Express Trailblazer ) and (99 00 01 02 03 C1 C2 C3 K1
K2 K3 LR4 LM4 LM7 LQ4 LQ9 GMC Sierra Savana Yukon Denalli Envoy) and (02 03 K6
K7 K8 Cadillac Escalade) and (03 Hummer N2) </P>

.</P>

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<TD align=left width=778><FONT size=1>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.
</FONT></TD>
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2003 HUMMER
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just an fyi in case someone else runs accross this code in the future.....
Problem was the leaking intake gasket specified in Klaus's posts. Thanks again Mr. Klaus!

Nothing $500 won't fix!