Hummer H1 Service Manual page 1155

90 PCM/Tech 1 Scan Tool
DTC P0501 - Vehicle Speed Sensor Circuit
Step
1 Important: 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" performed?
2 1. Install scan tool.
2. Raise drive wheels.
3. Engine operating.
4. Transmission in any drive range.
With drive wheels rotating, does vehicle speed increase with drive wheel
speed increase?
3 1. Transmission in park.
2. Back probe VSS buffer module ignition feed circuit with a test light con-
nected to ground. Is the test light "ON"?
4 Back probe VSS buffer module ignition feed circuit to the ground circuit
with a test light.
Is the test light "ON"?
5 1. Back probe VSS buffer module at VSS input circuit (C7) to the other
VSS input circuit (C12) with a J–39200 on the AC scale.
2. Transmission in any drive range with drive wheels rotating.
Does voltage increase on J–39200 with drive wheel increase?
6 Does scan tool display a trans output speed (MPH) increase with drive
wheel increase?
7 DTC is intermittent. If no additional DTCs are stored, refer to "Diagnostic
Aids". If additional DTCs are stored, refer those charts(s) first.
Are additional DTCs stored?
8 Repair the open in the ignition feed circuit.
Is action complete?
9 Repair the open in the ground circuit.
Is action complete?
10 Check the complete VSS input circuit for an open or short to ground.
Was a repair performed?
11 Check VSS output circuit for an open or short to ground.
Was a repair performed?
12 Check VSS output circuit for a poor connection at buffer module and PCM.
Was a repair performed?
13 Replace VSS buffer module.
Is action complete?
14 Replace the faulty PCM. Notice: If the PCM is faulty, the new PCM must
be programmed. Go to PCM replacement and programming procedures.
Is the action complete?
15 1. Using the Scan Tool, select "DTC", "Clear Info".
2. Start engine and idle at normal operating temperature.
3. Select "DTC", "Specific", then enter the DTC number which was set.
4. Operate vehicle within the conditions for setting this DTC as specified in
the supporting text.
Does the Scan Tool indicate that this diagnostic Ran and Passed?
16 Using the Scan Tool, select "Capture Info", "Review Info".
Are any DTCs displayed that have not been diagnosed?
_____________________________________________________
Action Value(s) Yes
— Go to Step 2.
— Go to Step 7.
— Go to Step 4.
— Go to Step 5.
— Go to Step 6. Go to Step 10.
— Go to Step 11. Go to Step 13.
— Go to
applicable
DTC table.
— Go to Step 15.
— Go to Step 15.
— Go to Step 15.
— Go to Step 15. Go to Step 12.
— Go to Step 15. Go to Step 14.
— Go to Step 15.
— Go to Step 15.
— Go to Step 16. Go to Step 2.
— Go to the
DTC table
®
No
Go to OBD
System Check.
Go to Step 3.
Go to Step 8.
Go to Step 9.
Go to
Diagnostic Aids
—
—
—
—
—
System OK.