Hummer H1 Service Manual page 1103

38 PCM/Tech 1 Scan Tool
DTC P0123 - Accelerator Pedal Position (APP) Sensor 1 Circuit High Voltage
Step
1 Important: Before clearing DTC(s) use the scan tool "Capture Info" to
record Freeze Frame and Failure Record for reference, as data will be lost
when "Clear Info" function is used.
Was the "On-Board Diagnostic (OBD) System Check" performed?
2 1. Ignition "ON", engine "OFF".
2. With the throttle closed, observe APP 1 display on the scan tool.
Is APP 1 above the specified value?
3 DTC is intermittent. If no additional DTCs are stored, refer to "Diagnostic
Aids". If additional DTCs were stored, refer to those chart(s).
4 1. Disconnect the APP sensor electrical connector.
2. Observe the APP 1 display on the Scan Tool.
Is APP 1 less than the specified value?
5 Probe APP 1 sensor ground circuit at the APP sensor harness connector
with a test light connected to B+.
Is the test light "ON"?
6 1. Check for a short to voltage on the APP 1 sensor signal circuit.
2. If the APP 1 sensor signal circuit is shorted, repair it as necessary.
Was the APP 1 sensor signal circuit shorted?
7 Check for poor electrical connections at the APP sensor and replace termi-
nals if necessary.
Did any terminals require replacement?
8 1. Check for an open sensor ground circuit.
2. If a problem is found, repair as necessary.
Was APP 1 sensor ground circuit open?
9 Replace the APP module.
Is Action complete?
10 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?
11 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?
12 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 OBD Sys-
4.75v Go to Step 4. Go to Step 3.
— Go to the
applicable
DTC table.
.25v Go to Step 5. Go to Step 6.
— Go to Step 7.
— Go to Step 11. Go to Step 10.
— Go to Step 11. Go to Step 9.
— Go to Step 11. Go to Step 10.
— Go to Step 11.
— Go to Step 11.
— Go to Step 12. Go to Step 2.
— Go to the
applicable
DTC table
®
No
tem Check.
Go to
Diagnostic
Aids.
Go to Step 8.
—
—
System OK