Hummer H1 Service Manual page 815

12-44 Electrical System
Step
1 Important: Before clearing the DTC's use the scan
tool Capture Info in order to record the Freeze
Frame and the failure records for reference, as the
data will be lost when the clear function is used.
Was the On-Board Diagnostic (OBD) System
Check performed?
2 Turn the ignition OFF for 10 seconds. Turn the
ignition ON. Does the fuel pump operate during
the glow plug cycle?
3 Disconnect the fuel lift pump connector. Using a
DVOM set to measure voltage, place the ground
lead on a known good ground, and the positive
lead on the grey wire (CKT787) at the fuel lift
pump engine harness connector. Turn the ignition
OFF for 10 seconds. Turn the ignition ON. Is volt-
age present?
4 Place ground lead of DVOM on the black wire
(CKT57) at the fuel lift pump engine harness con-
nection.With the positive lead still on the grey
wire (CKT787) Turn the ignition OFF for 10 sec-
onds. Turn the ignition ON. Is voltage present?
5 Reconnect the fuel lift pump, Disconnect the fuel
lift pump relay. Using a DVOM set to measure
voltage, place the ground lead on known good
ground, and place the positive lead on the org wire
(CKT537). Is voltage present?
6 Place the ground lead of the DVOM set to mea-
sure voltage on the black wire (CKT57). With the
positive lead still on the org wire (CKT537). Is
voltage present?
7 Using a DVOM set to measure voltage, place the
ground lead on the black wire (CKT57)on the fuel
lift pump relay connection. Place the positive lead
on the dark green wire (CKT238). Turn the igni-
tion OFF for 10 seconds. Turn the ignition ON. Is
voltage present?
8 Reconnect the fuel lift pump relay. Using the scan
tool, command the fuel pump relay "on". Does the
pump run?
4-1-00
_______________________________________________________
Fuel Lift Pump Inoperative VIN Z
Action Value(s) Yes
Go to step 2.
System OK,
problem may be
intermittent.
12v Go to step 4.
12v Replace fuel lift
pump.
12v Go to step 6.
12v Go to step 7.
12v Replace the fuel
lift pump relay.
12v Check for open
in CKT787
between the fuel
lift pump relay
and the PCM
32pin xxxx con-
nector pin D5.
®
No
Go to Power-
train OBD sys-
tem check.
Go to step 3.
Go to step 5.
Go to step 5.
Repair open or
short to ground
in CKT537
between fuel
pump relay and
fuse 2D.
Repair open or
short to ground
in CKT57
between fuel
pump relay and
engine ground.
Go to step 8.
Go to step 9.