Hummer H1 (2002+). Manual — part 205

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Electrical System 12-47

®

05745159

Fuel Tank Selector System Inoperative (No Tank Switch)

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 refer-
ence, as the data will be lost when the clear func-
tion 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?

Go to step 3.

Diagnose Fuel
lift pump first.

3

Remove fuel tank selector switch from dash, and
disconnect switch from harness. Using a DVOM
set to measure resistance, probe the black wire of
the fuel selector switch connector (CKT 59) with
the black lead, and the positive lead on the ground
studs at left of dash.Is resistance below specifica-
tion?

<.2

Ω

Go to step 4

Repair open or
bad connection
in CKT 59
between fuel
selector switch
and IP ground
studs.

4

Using a DVOM set to measure voltage, place the
ground lead on the negative studs to right of the
IP panel. Place the positive lead on the grey wire
(CKT 787) at the fuel tank selector switch. Turn
the ignition OFF for 10 seconds. Turn the ignition
ON. Does the meter read voltage?

12 v

Go to step 5

Repair open or
short to ground
in CKT 787 fuel
pump relay and
fuel selector
switch

5

Re-connect fuel tank selector switch. Using a
DVOM set to measure voltage, backprobe the red
wire (CKT 786) with the negative lead and brown
wire (CKT 789) with the positive lead.Turn the
ignition OFF for 10 seconds. Turn the ignition
ON. With the switch in the AUX position voltage
should be present, when the switch is moved to
the MAIN position, reverse polarity voltage
should be present. If fuel pump shuts off during
test, repeat cycle of key. Does meter show oppo-
site voltages when moved between AUX and
MAIN

12 v+=AUX

12 v-=MAIN

Go to step 5.

Replace fuel
tank selector
switch and
recheck system.

6

Disconnect fuel selector valve electrical connec-
tion. Using a DVOM set to measure voltage,
probe the brown wire with the positive lead, and
the red lead with the negative lead. Turn the igni-
tion OFF for 10 seconds. Turn the ignition ON.
With the switch in the AUX position voltage
should be present, when the switch is moved to
the MAIN position, reverse polarity voltage
should be present. Does meter show opposite
voltages when moved between AUX and MAIN

12 v+=AUX

12 v-=MAIN

Replace fuel
selector valve

Go to step 7.

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12-48

Electrical System

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®

7

Relocate the ground lead of the DVOM set to
measure voltage to a known good ground. Turn
the ignition OFF for 10 seconds. Turn the ignition
ON, and the tank selector switch in the AUX posi-
tion, probe the brown wire (CKT 789) with the
positive meter lead. Is voltage present?

12 v

Go to step 8.

Repair open,
bad connection
or short to
ground in CKT
789 between the
fuel selector
switch and
valve.

8

Turn the ignition OFF for 10 seconds. Turn the
ignition ON, and the tank selector switch in the
MAIN position, probe the red wire (CKT 786)
with the positive meter lead, the ground lead
should be on a know good ground. Is voltage
present?

12 v

No electrical
problems found,
problem may be
intermittent or
mechanical.

Repair open,
bad connection
or short to
ground in CKT
786.

Fuel Tank Selector System Inoperative (No Tank Switch)

Step

Action

Value(s)

Yes

No

4-1-00

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Electrical System 12-49

®

05745159

Figure 2-74: Fuel Selector Valve Schematic

EXTERIOR
FUSE BOX

G2

G4

FUSE 2D
20A
INTERIOR
FUSE BOX

HOT AT

ALL TIMES

FUEL

SELECTOR

SWITCH

G4

TO DIMMER

MODULE

FUEL

GAUGE

TO

GAUGE

FUSE

I

G

L

S

FUEL
SELECTOR
VALVE

FUEL LEVEL
SIGNAL OUT

17 PP

30 GY

29 PK

C26-B

C2-35

C1-35

AUX TANK

FUEL LEVEL

SIGNAL

MAIN TANK

FUEL LEVEL

SIGNAL

TANK

CHANGE

CONTROL

TANK

CHANGE

CONTROL

C26-C

675 YL

673 DB

C1

C3

C2

C26

75

M6

37

E

9

M7

36

D

786 RD

3

789 BR

1

6

4

2B

5B

C3-N6

59 BK

787 GY

C3-M8

C1-11

TO FUEL
LIFT
PUMP

C27-D8

85

87 87A

86

30

PCM

C1-10

537 OR

9-S12-057

59 BK

FUEL
LIFT PUMP
RELAY

238 DG

G2

A

AUX TANK
FUEL LEVEL
SENDING UNIT

MAIN TANK

FUEL LEVEL

SENDING UNIT

59 BK

C26-A

B

C38-C

C3-P7

Training 8F

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12-50

Electrical System

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Figure 2-75: Fuel Manager Schematic

FUSE 3B
20AMP
EXTERIOR
FUSE BOX

DRAIN
FILTER

HOT IN RUN
AND START

WATER IN
FUEL LIGHT
LEFT HAND
STATUS CENTER

C9-D

C3-F4

C1-45

B

A

327 YL

C

C9-J

WATER IN
FUEL
SENSOR

FUEL
HEATER

291 PK

57 BK

G2

57 BK

C

A

9-S12-154

FUSE 4B
5AMP
INTERIOR
FUSE BOX

TO

IGNITION

SWITCH

C3-N7

30 GY

4-1-00