Hummer H2. Manual — part 1645

percent. The values for the Short Term fuel trim 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.
A block of cells contain information arranged in combinations of engine RPM and engine load for a full range
of vehicle operating conditions. The long term fuel trim diagnostic is based on an average of cells currently
being used. The PCM selects the cells based on the engine speed and engine load. The fuel trim diagnostic will
conduct a test to determine if a rich failure actually exists or if excessive vapor from the evaporative emission
(EVAP) canister is causing a rich condition. If the PCM detects an excessively rich condition, DTC P0172 or
P0175 sets.

Conditions for Running the DTC

z

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

z

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

z

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

z

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

z

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

z

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

z

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

z

The mass air flow (MAF) is between 5-90 g/s.

z

The fuel level is more than 10 percent.

z

The throttle position (TP) is less than 90 percent.

Conditions for Setting the DTC

z

The average long term fuel trim value is below -13 percent.

z

All of the above conditions are present for 40 seconds.

Action Taken When the DTC Sets

z

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

z

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

z

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

z

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

z

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

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0171/P0174 To DTC P0507 (TAC)) - 4.8L, 5.3L, and

6.0L - Hummer H2

emission related diagnostic.

z

Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

z

Fuel contamination, such as water or alcohol will effect fuel trim.

z

A malfunctioning mass air flow sensor can cause a rich condition and set this DTC. Refer to DTC P0101
(With Throttle Actuator Control) .

z

Use a scan tool in order to 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.

5: If conditions were not corrected, refer to Fuel System Diagnosis for a possible fuel problem.

6: An EVAP canister that is saturated will cause a rich condition. If the conditions were not corrected, a
worn cam, worn intake or exhaust valves, or other engine mechanical failure may be the problem.

DTC P0172 or P0175

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

1. Install scan tool.

2. Start and idle the engine at the normal

operating temperature in Closed Loop.

3. Record the long term fuel trim data.

4. Turn OFF the engine.

5. Turn ON ignition, with the engine OFF.

6. Review the Freeze Frame/Failure Records,

and record the displayed data for this DTC.

Does the scan tool indicate that the long term
fuel trim is less than the specified value?

IMPORTANT:

If any DTCs other than P0172 are set, refer to
those DTCs before continuing.

-13%

Go to Step 3

Go to Diagnostic Aids

3

1. Operate engine at idle.

2. Observe HO2S parameters with a scan

tool.

200-

800
mV

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0171/P0174 To DTC P0507 (TAC)) - 4.8L, 5.3L, and

6.0L - Hummer H2

Does the scan tool indicate that the values are
within the specified range and fluctuating?

Go to Step 4

Go to Step 5

4

1. Turn OFF engine.

2. Visually and physically inspect the

following items:

z

The evaporative emissions (EVAP)
lines and components for damage or
blockage-Refer to Evaporative
Emissions (EVAP) Hose Routing
Diagram .

z

The inlet screen of the mass air flow
(MAF) sensor for blockage.

z

The vacuum hoses for splits, kinks,
and proper connections-Refer to
Emission Hose Routing Diagram .

z

The air intake duct for being
collapsed or restricted.

z

The air filter for being dirty or
restricted.

z

Check for objects blocking the
throttle body.

Did you find and correct the condition?

-

Go to Step 7

Go to Step 6

5

1. Turn OFF engine.

2. Inspect the heated oxygen sensor (HO2S)

for proper installation.

3. Inspect to ensure that the electrical

connectors and the wires are secure and
not contacting the exhaust system.

4. Test for continuity between the signal

circuit and the low reference circuit. Refer
to Circuit Testing and Wiring Repairs in
Wiring Systems.

Did you find and correct the condition?

-

Go to Step 7

Go to Fuel System

Diagnosis

6

Inspect for the following:

z

Excessive fuel in the crankcase.

z

Proper operation of the fuel pressure
regulator - Refer to Fuel System
Diagnosis .

z

All injectors are functioning properly -
Refer to Fuel Injector Coil Test .

-

Go to Symptoms -

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0171/P0174 To DTC P0507 (TAC)) - 4.8L, 5.3L, and

6.0L - Hummer H2

DTC P0200

Circuit Description

The control module enables the appropriate fuel injector pulse for each cylinder. Ignition voltage is supplied to
the fuel injectors. The control module controls each fuel injector by grounding the control circuit via a solid
state device called a driver. The control module monitors the status of each driver. If the control module detects
an incorrect voltage for the commanded state of the driver, DTC P0200 sets.

Conditions for Running the DTC

z

The engine speed is more than 400 RPM.

z

The ignition voltage is between 6-18 volts.

Conditions for Setting the DTC

z

The powertrain control module (PCM) detects an incorrect voltage on a fuel injector control circuit.

z

The condition exists for 5 seconds.

Action Taken When the DTC Sets

z

The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition

Did you find and correct the condition?

Go to Step 7

Engine Mechanical in

Engine Mechanical -

4.8L, 5.3L, and 6.0L

7

1. Clear the DTCs with a scan tool.

2. Turn OFF the ignition for 30 seconds.

3. Start the engine.

4. 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.

Did the DTC fail this ignition?

IMPORTANT:

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

-

Go to Step 2

Go to Step 8

8

Observe the Capture Info with a scan tool.
Are there any DTCs that have not been
diagnosed?

-

Go to

Diagnostic

Trouble Code

(DTC) List

System OK

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0171/P0174 To DTC P0507 (TAC)) - 4.8L, 5.3L, and

6.0L - Hummer H2