Hummer H1 (2002+). Manual — part 204

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Electrical System 12-43

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05745159

Figure 2-72: Glow Plug Control Circuit Schematic

30

Use a scan tool to clear the DTC’s. Start the
engine. Allow the engine to idle until the engine
reaches normal operating temperature. Select the
DTC and the specific DTC function. Enter the
DTC number which was set. Operate the vehicle,
with the Conditions for Setting this DTC, until
the scan tool indicates the diagnostic Ran.
Does the scan tool indicate the diagnostic Passed?

Go to step 31.

Go to step 2.

31

Does the scan tool display any addition undiag-
nosed DTC’s?

Go to the appli-

cable DTC

table.

System OK.

Glow Plugs Inoperative (Cont’d)

Step

Action

Value

Yes

No

FUSE 3A
20 AMP
EXTERIOR

HOT IN RUN
AND START

GLOW PLUG
RELAY

IGN

POWER

FUSIBLE
LINK

W

AIT

WAIT TO START
LAMP CONTROL

C9-J

C9-A

C3-D1

C1-27

C28-C7

GLOW PLUGS RH

GLOW PLUG

RELAY

CONTROL

GLOWPLUG

FEEDBACK

SIGNAL

POWERTRAIN
CONTROL
MODULE
(PCM)

C27-D7

C27-C6

30 GY

466 YL

G1

#1

#3

#5

#7

BK

C5-A4

338 DB

C3-N7

RIGHT
BANK
OUTPUT

00-S12-011

B+

C5-C11

C5-B4

GLOW PLUGS LH

#2

#4

#6

#8

BATT +

LEFT

BANK

OUTPUT

RH STATUS

CENTER

5V

506 LB

239 PK

A

C

TO

STARTER

POS. STUD

B

B

C

D

A

D

C

B

A

D

FUSE 4B
5 AMP
INTERIOR
FUSE BOX

TO

IGNITION

SWITCH

4-1-00

12-44

Electrical System

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Fuel Lift Pump Inoperative VIN Z

Step

Action

Value(s)

Yes

No

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?

Go to step 2.

Go to Power-
train OBD sys-
tem check.

2

Turn the ignition OFF for 10 seconds. Turn the
ignition ON. Does the fuel pump operate during
the glow plug cycle?

System OK,
problem may be
intermittent.

Go to step 3.

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?

12v

Go to step 4.

Go to step 5.

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?

12v

Replace fuel lift
pump.

Go to step 5.

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?

12v

Go to step 6.

Repair open or
short to ground
in CKT537
between fuel
pump relay and
fuse 2D.

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?

12v

Go to step 7.

Repair open or
short to ground
in CKT57
between fuel
pump relay and
engine ground.

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?

12v

Replace the fuel
lift pump relay.

Go to step 8.

8

Reconnect the fuel lift pump relay. Using the scan
tool, command the fuel pump relay “on”. Does the
pump run?

12v

Check for open
in CKT787
between the fuel
lift pump relay
and the PCM
32pin xxxx con-
nector pin D5.

Go to step 9.

4-1-00

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Electrical System 12-45

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05745159

9

Disconnect fuel lift pump relay.Using a DVOM
set to measure ohms, measure resistance between
C27-D5, and the fuel lift pump relay dark green
wire (CKT238). Does resistance exceed specifica-
tions?

<.2

Ω

Repair open or
bad connection
in CKT 238
between PCM
and fuel lift
pump relay.

Go to step 10.

10

Using a DVOM set to measure ohms, measure
continuity to ground between the dark green
wire(CKT238) and engine ground. Is continuity
present?

Repair short to
ground in
CKT238.

Go to step 11.

11

Replace PCM. Is repair complete?

Go to step 12.

12

Turn the ignition OFF for 10 seconds. Turn the
ignition ON. Does the fuel pump operate during
the glow plug cycle?

Repair com-
pleted.

Go to step 1.

Fuel Lift Pump Inoperative VIN Z (Cont’d)

Step

Action

Value(s)

Yes

No

4-1-00

12-46

Electrical System

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Figure 2-73: Fuel Lift Pump Schematic

FUSE 2D
20A
INTERIOR

FUEL PUMP
RELAY
EXTERIOR
FUSE BOX

C1-10

G2

POWERTRAIN

CONTROL

MODULE

FUEL PUMP

RELAY CONTROL

FUEL LIFT
PUMP SIGNAL

TO FUEL

SELECTOR SWITCH

M

G2

FUEL
LIFT
PUMP

B

A

57 BK

787 GY

787 GY

787 GY

C27-D5

57 BK

C27-D8

238 DG

537 OR

9-S12-051

4-1-00