Hummer H2. Manual — part 1621

Circuit Description

The manifold absolute pressure (MAP) sensor responds to pressure changes in the intake manifold. The
pressure changes occur based on the engine load. The MAP sensor has the following circuits:

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5-volt reference circuit

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Low reference circuit

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MAP sensor signal circuit

The powertrain control module (PCM) supplies 5 volts to the MAP sensor on the 5-volt reference circuit. The
PCM also provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the
MAP sensor signal circuit which is relative to the pressure changes in the manifold. The PCM should detect a
low signal voltage at a low MAP, such as during an idle or a deceleration. The PCM should detect a high signal
voltage at a high MAP, such as the ignition is ON, with the engine OFF, or at a wide open throttle (WOT). The
MAP sensor is also used in order to determine the barometric pressure (BARO). This occurs when the ignition
switch is turned ON, with the engine OFF. The BARO reading may also be updated whenever the engine is
operated at WOT. The PCM monitors the MAP sensor signal for voltage outside of the normal range.

The PCM calculates a predicted value for the MAP sensor based on the throttle position (TP) and the engine
speed. The PCM then compares the predicted value to the actual MAP sensor signal. If the PCM detects that the
MAP sensor signal is not within the predicted range, DTC P0106 sets.

Conditions for Running the DTC

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DTCs P0068, P0101, P0102, P0103, P0107, P0108, P0120, P0220, P0442, P0443, P0446, P0455, P1125,
P1516, P2101, P2108, P2120, P2121, P2125, P2135 are not set.

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The engine is running.

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The engine speed is between 400-5,000 RPM.

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Any change in the engine speed is less than 125 RPM.

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The traction control, if equipped, is not active.

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The power take-off (PTO), if equipped, is not active.

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The A/C compressor clutch state does not change.

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The clutch switch state does not change, if equipped with a manual transmission.

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The power steering load is stable.

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The brake switch state does not change.

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The above conditions are met for 1 second.

Conditions for Setting the DTC

The PCM detects that the actual MAP sensor signal is not within the predicted range for 2 seconds.

Action Taken When the DTC Sets

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

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0068 To DTC P0141/P0161) - 4.8L, 5.3L, and 6.0L -

Hummer H2

cycle that the diagnostic runs and fails.

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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

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

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

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

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Clear the MIL and the DTC with a scan tool.

Test Description

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

4: This step tests the ability of the MAP sensor to correctly indicate barometric pressure.

6: This step tests the ability of the MAP sensor to respond to an increase in engine vacuum.

8: This step tests for a proper MAP sensor pressure with an applied vacuum.

13: This step calculates the resistance in the 5-volt reference circuit.

14: This step calculates the resistance in the low reference circuit.

DTC P0106 (With Throttle Actuator Control)

Step

Action

Values

Yes

No

Schematic Reference:Engine Controls Schematics
Connector End View Reference:Engine Controls Connector End Views or Powertrain Control
Module (PCM) Connector End Views

1

Did you perform the Diagnostic System Check-Engine
Controls?

-

Go to Step 2

Go to Diagnostic

System Check -

Engine Controls

2

Inspect for the following conditions:

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A disconnected, damaged, or incorrectly routed
vacuum hose

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A missing or damaged manifold absolute pressure
(MAP) sensor seal

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Any restrictions in the MAP sensor vacuum source

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Any vacuum leaks in the intake manifold

-

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0068 To DTC P0141/P0161) - 4.8L, 5.3L, and 6.0L -

Hummer H2

Did you find and correct the condition?

Go to Step 21

Go to Step 3

3

Do you have access to another vehicle in which the MAP
sensor pressure can be observed with a scan tool?

IMPORTANT:

The vehicle used for the comparison is not limited to
the same type of vehicle as is being serviced. A
vehicle known to provide an accurate reading is
acceptable.

-

Go to Step 4

Go to Step 5

4

1. Turn ON the ignition, with the engine OFF.

2. Observe the MAP sensor pressure with the scan

tool.

3. Observe the MAP sensor pressure in the known

good vehicle with the scan tool.

4. Compare the values.

Is the difference between the values less than the
specified value?

3 kPa

Go to Step 6

Go to Step 11

5

1. Turn ON the ignition, with the engine OFF.

2. Observe the MAP sensor pressure with the scan

tool. Refer to Altitude vs Barometric Pressure .

3. The MAP sensor pressure should be within the

range specified for your altitude.

Does the MAP sensor indicate the correct barometric
pressure?

IMPORTANT:

The Altitude vs. Barometric Pressure table indicates a
pressure range for a given altitude under normal
weather conditions. Weather conditions consisting of
very low or very high pressure and/or very low or very
high temperature may cause a reading to be slightly
out of range.

-

Go to Step 6

Go to Step 11

6

1. Observe the MAP sensor pressure with the scan

tool.

2. Start the engine.

Does the MAP sensor pressure change?

-

Go to Step 7

Go to Step 11

1. Turn OFF the ignition.

2. Remove the MAP sensor from the intake manifold.

Leave the MAP sensor connected to the electrical
harness.

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0068 To DTC P0141/P0161) - 4.8L, 5.3L, and 6.0L -

Hummer H2

7

3. Connect a J 23738-A Mityvac to the MAP sensor

port.

4. Turn ON the ignition, with the engine OFF.

5. Observe the MAP sensor pressure with the scan

tool.

6. Apply vacuum to the MAP sensor with the J

23738-A in 1 inch Hg increments until 15 inch Hg
is reached. Each 1 inch Hg should decrease the
MAP sensor pressure by 3-4 kPa.

Is the decrease in MAP sensor pressure consistent?

-

Go to Step 8

Go to Step 11

8

1. Observe the MAP sensor pressure with the scan

tool.

2. Apply vacuum with the J 23738-A until 20 inches

Hg is reached.

Is the MAP sensor pressure less than the specified value?

34 kPa

Go to Step 9

Go to Step 11

9

1. Observe the MAP sensor pressure with the scan

tool.

2. Disconnect the J 23738-A from the MAP sensor.

Does the MAP sensor pressure return to the original
reading observed in Step 4 or Step 5?

-

Go to Step 10

Go to Step 11

10

Inspect for the following engine conditions:

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Incorrect cam timing-Refer to Timing Chain and
Sprockets Replacement in Engine Mechanical for
the correct timing.

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A restricted exhaust flow-Refer to Restricted
Exhaust in Engine Exhaust.

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Any worn piston rings-Refer to Engine
Compression Test in Engine Mechanical.

Did you find and correct the condition?

-

Go to Step 21

Go to

Intermittent

Conditions

11

Test for an intermittent and for a poor connection at the
MAP sensor. Refer to Testing for Intermittent
Conditions and Poor Connections and Connector
Repairs in Wiring Systems.
Did you find and correct the condition?

-

Go to Step 21

Go to Step 12

1. Disconnect the MAP sensor harness connector.

2. Measure the voltage from the 5-volt reference

circuit of the MAP sensor to a good ground with a

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0068 To DTC P0141/P0161) - 4.8L, 5.3L, and 6.0L -

Hummer H2