Hummer H1 Service Manual page 1132

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DTC P0231 - Fuel Lift Pump Secondary Circuit Low Voltage
Step
1 Important: Before clearing DTC(s) use the scan tool "Capture Info".
Was the "On-Board Diagnostic (OBD) System Check" performed?
2 1. Turn the ignition "OFF" for 20 seconds.
2. Turn the ignition "ON".
3. Listen for the fuel lift pump.
Does the lift pump operate during glow plug cycle and then turn "OFF"?
3 1. Turn the ignition "OFF".
2. Probe the fuel pump test terminal with a fused jumper to "B+".
Does the fuel pump operate?
4 1. Disconnect the fuel pump relay.
2. Probe the fuel pump test terminal with a fused jumper to "B+".
Does the fuel pump operate?
5 Replace the faulty fuel pump relay.
Is the action complete?
6 Check for a an open fuel pump signal circuit.
Was a problem found?
7 Repair the open fuel pump signal circuit.
Is the action complete?
8 1. Turn the ignition "OFF".
2. Remove the fuel pump relay.
3. Connect a test light to ground.
4. Probe the fuel pump relay harness connector terminal number "B1".
Is the test light "ON"?
9 Repair the open in the battery feed circuit to the fuel pump relay.
Is the action complete?
10 Connect a test light between terminal number "B1" and terminal number
"A1" of the fuel pump relay harness connector.
Is the test light "ON"?
11 Repair the open fuel pump relay ground circuit.
Is the action complete?
12 1. Turn the ignition "OFF".
2. Connect a test light between terminal number "B3" and ground.
3. Monitor the test light.
4. Turn the ignition "ON".
Was a problem found?
13 Check for an open in circuit from fuel pump relay harness connector termi-
nal number "B3" and PCM.
Was a problem found?
14 Repair the open in the fuel pump relay control circuit.
Is the action complete?
15 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?
16 Check for a faulty connection at fuel pump relay harness connector terminal
number "B3".
Was a problem found?
17 Replace the faulty fuel pump relay.
Is the action complete?
05745159
Action
PCM/Tech 1 Scan Tool 67
Value(s) Yes
— Go to Step 2. Go to OBD Sys-
— Go to
Diagnostic
Aids.
— Go to Step 8.
— Go to Step 5. Go to Step 6.
— Go to Step 6.
— Go to Step 7.
— Go to Step 8.
— Go to Step 10. Go to Step 9.
— Go to Step 10.
— Go to Step 12. Go to Step 11.
— Go to Step 12.
— Go to Step 16. Go to Step 13.
— Go to Step 14. Go to Step 15.
— Go to Step 15.
— Go to Step 16.
— Go to Step 18. Go to Step 17.
— Go to Step 18.
No
tem Check.
Go to Step 3.
Go to Step 4.
—
Go to Step 8.
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