Hummer H1 Service Manual page 273

5-74 Transmission/Transfer Case
Conditions for Clearing the DTC
1. The PCM tuns OFF the MIL after three consecutive igni-
tion cycles without a failure reported.
2. A scan tool can clear the DTC from the PCM history. The
PCM clears the DTC from the PCM history if the vehicle
completes 40 warm-up cycles without a failure reported.
3. The PCM cancels the DTC default actions when the fault
no longer exists and the ignition is OFF long enough in
order to power down the PCM.
Diagnostic Aids
• Inspect the wiring for poor electrical connections at the
PCM. Inspect the wiring for poor electrical connections at
the transmission 20-way connector. Look for the following
problems:
• A bent terminal
• A backed out terminal
• A damaged terminal
• Poor terminal tension
• A chafed wire
• A broken wire inside the insulation
Step
1 Was the Powertrain On-Board Diagnostic (OBD) Sys-
tem Check Performed?
2 1. Install the scan tool (Tech 1).
2. With the engine OFF, turn the ignition switch to the
RUN position.
Important: Before clearing the DTCs, use the scan tool
in order to record the Freeze Frame and Failure Records
for reference. The Clear Info function will erase the
data.
3. Record the DTC Freeze Frame and Failure Records
and DTCs.
4. Raise and support the drive wheels.
5. Start the engine and place the transmission in D3
range.
6. With the Drive wheels rotating, slowly accelerate to
2000 RPM and hold.
Does the Transmission OSS drop or fluctuate more than
the specified value?
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DTC P0723 Output Speed Sensor Intermittent
Action
• It may be necessary to drive the vehicle.
• When diagnosing for an intermittent short or open, mas-
sage the wiring harness while watching the test equipment
for a change.
Test Description
The numbers below refer to the numbers on the diagnostic ta-
ble.
2. This step verifies the fault condition.
4. This step verifies the OSS Sensor and circuit output to the
VSS Buffer Module.
7. This step tests the voltage supply to the VSS Buffer
Module.
9. This step tests the integrity of the ground circuit.
Value
—
1000 RPM
Yes No
Go to Power-
train OBD
Go to Step 2 System Check
No fault veri-
fied at this
time. Go to
Diagnostic
Go to Step 3 Aids
®