Hummer H1 (2006+). Manual - part 84

OBD-180

On-Board Diagnostics

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DTC P0500 Vehicle Speed Sensor (VSS) Circuit (Figure OBD-52)

Figure OBD-52:   Vehicle Speed Sensor (VSS) Circuit

Circuit Description

The vehicle speed sensor (VSS) monitors the rotation speed of the transmission output shaft. The VSS assembly is a permanent
magnet generator. It produces an AC voltage as the rotor teeth on the output shaft of the transmission, 2WD, or transfer case, 4WD,
pass through the magnetic field of the sensor. The AC voltage frequency and amplitude increase as the vehicle speed increases.
The engine control module (ECM) that operates in a range of -4.5 volts or +5.0 volts. The ECM converts this signal into vehicle
speed. As vehicle speed increases, the frequency of the duty cycle will increase.

Conditions for Setting the DTC

If the ECM detects a difference in vehicle speed with the VSS of greater than 8 km/h (5 mph), then DTC P0500 is set.

Action Taken When the DTC Sets 

• The ECM illuminates the malfunction indicator lamp (MIL) on the second consecutive drive trip that the diagnostic runs. 

• The ECM disables cruise control. 

• The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this informa-

tion as Freeze Frame and Failure Records. 

• The ECM stores DTC P0500 in ECM history. 

Conditions for Clearing the MIL/DTC 

• The ECM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes. 

• A scan tool can clear the MIL/DTC. 

• The ECM clears the DTC from ECM history if the vehicle completes 40 warm-up cycles without an emission related diag-

nostic fault occurring. 

• The ECM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the ECM. 

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 On-Board Diagnostics  OBD-181

5745804

Step

Action

Value(s)

Yes

No

    1

NOTE: Before clearing DTC(s) use the scan tool “Capture info”
to record Freeze Frame and Failure Records for reference, as data
will be lost when “Clear Info” function is used 

Was the “On-Board Diagnostic (OBD) System Check” per-
formed?

Go to step 2.

Go to OBD Sys-

tem Check.

    2

1.

Install a scan tool.

2.

Turn ON the ignition, with the engine OFF.

NOTE: Before clearing the DTC, use the scan tool in order to
record the Freeze Frame and Failure Records from the TCM. 

NOTE: Using the Clear Info function erases stored DTCs in both
the TCM and ECM. 

3.

Record the DTC Freeze Frame and Failure Records.

Is there a DTC P0721 or P0722 present?

Go to  P0721   

P0722

Go to Step 3

    3

1.

Install a scan tool.

2.

Turn ON the ignition, with the engine OFF.

NOTE: Before clearing the DTC, use the scan tool in order to
record the Freeze Frame and Failure Records from the ECM. 

NOTE: Using the Clear Info function erases stored DTCs in both
the ECM and TCM. 

3.

Record the DTC Freeze Frame and Failure Records.

4.

Clear the DTC.

WARNING:   To avoid any vehicle damage, serious per-
sonal injury or death when major components are re-
moved from the vehicle and the vehicle is supported by a
hoist, support the vehicle with jack stands at the opposite
end from which the components are being removed.

5.

Raise and support the vehicle.

6.

Start and idle the engine.

7.

Turn off the traction control system, if equipped.

8.

Select and monitor Engine Data 1/Vehicle Speed on the scan 
tool.

9.

Place the transmission into DRIVE. With the drive wheels 
rotating, slowly increase the engine speed.

Does Vehicle Speed on the scan tool increase with wheel speed?

Go to Intermit-

tent Conditions 

Go to Step 4

    4

1.

Turn OFF the engine.

2.

Disconnect connector C76 at the ECM.

3.

Turn the ignition to the ON position.

4.

Using the DVOM and the J 35616 GM terminal test kit, test 
the signal circuit for voltage between pin 21 and ground.

Is the circuit voltage within the specified range?

OBD-182

On-Board Diagnostics

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    5

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?

Go to Step 2 

Go to Step 13

   6

1.

Using the Scan Tool select “Capture Info,” Review Info.” Are 
any DTC’s displayed that have not been diagnosed?

Go to the appli-

cable DTC 

table.

System OK.

Step

Action

Value(s)

Yes

No

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 On-Board Diagnostics  OBD-183

5745804

DTC P0506 Idle Speed Too Low

Circuit Description

The engine control module (ECM) adjusts the fuel delivery in order to control crankshaft speed at idle. If the ECM detects the en-
gine speed is incorrect for the amount of fuel that is delivered, DTC P0506 sets.

Conditions for Setting the DTC

The actual idle speed is more than 100 RPM under the target idle speed.

Action Taken When the DTC Sets 

• The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diag-

nostic 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 consecu-
tive 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. 

Step

Action

Value(s)

Yes

No

    1

NOTE: Before clearing DTC(s) use the scan tool “Capture info”
to record Freeze Frame and Failure Records for reference, as data
will be lost when “Clear Info” function is used 

Was the “On-Board Diagnostic (OBD) System Check” per-
formed?

Go to step 2.

Go to OBD Sys-

tem Check.

    2

Are any other DTCs set?

Go to the DTC 

in order