Hummer H1 Service Manual page 1181

116 PCM/Tech 1 Scan Tool
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. Turn the ignition ON leaving the engine OFF.
2. Using a scan tool, command the Glow Plug system ON.
Does the lamp turn ON?
3 The DTC is intermittent. If no additional DTCs are stored, refer to Diag-
nostic Aids. If additional DTCs were stored refer to those tables(s)
Are additional DTCs stored?
4 1. Turn the ignition OFF.
2. Disconnect the PCM connector containing the Wait To Start lamp con-
trol circuit.
3. Turn the ignition ON leaving the engine OFF.
Is the lamp OFF?
5 With a fused jumper wire connected to ground, probe the Wait to Start
lamp control circuit in the PCM harness connector.
Is the lamp ON?
6 Check the connections at the PCM.
Was a repair performed?
7 The Wait To Start lamp control circuit is shorted to ground, repair as nec-
essary.
Is the action complete?
8 Check the Wait To Start circuit for the following:
• Open ignition feed to the bulb
• malfunctioning bulb
• Control circuit open or shorted to B+
Was a repair performed?
9 Replace the PCM.
Is the action complete?
10 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?
11 Does the Scan tool display any additional undiagnosed DTCs?
___________________________________________________
DTC P1643 Wait to Start Lamp Control Circuit
Action Value(s) Yes
Go to step 2
Go to step 3
Go to the
applicable
DTC table
Go to step 5
Go to step 6
Go to step 10
Go to step 10
Go to step 10
Go to step 10
Go to step 11
Go to the
Applicable
DTC table
®
No
Go to Power-
train OBD
System
Checke
Go to step 4
Go to Diag-
nostic Aids
Go to step 7
Go to step 8
Go to step 2
System OK