Fuel Gauge Inoperative - Hummer H1 Service Manual

12-72 Electrical System
Step
1 Using a DVOM set to measure voltage, check for
voltage at the rear of the fuel gauge on the grey
wire(CKT30) connect negative meter lead to
ground on black wire(CKT59). With ignition on,
is voltage present?
2 Move the negative meter lead to a known good
ground. IS voltage present?
3 With the ignition on, ground the signal lead does
the gauge go to Full?
4 Disconnect fuel selector valve. Using a jumper
wire, ground the pink wire(CKT29). With the
ignition on does the fuel gauge go to full?
5 Determine fuel level in the main tank. Using a
DVOM set to measure resistance, measure resis-
tance to ground on the blue wire(CKT673). Does
resistance value correspond with fuel level in
tank.
6 Determine fuel level in the auxiliary tank. Using a
DVOM set to measure resistance, measure resis-
tance to ground on the yellow wire(CKT675).
Does resistance value correspond with fuel level
in tank.
7 Gain access to fuel level sending unit connectors.
Using a DVOM set to measure resistance, check
resistance through the sending unit. Does resis-
tance value correspond with the fuel level in the
tank?
4-1-00
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Fuel Gauge Inoperative

Action Value(s) Yes
12v Go to step 3.
12v Repair open or
bad connection
in CKT59
between fuel
gauge and G4.
Full Go to step 4.
Full Go to step 5.
Empty=268Ω Go to step 6.
Half=124.4Ω
Full=19.3Ω
Empty=268Ω Replace fuel
Half=124.4Ω selector valve.
Full=19.3Ω
Empty=268Ω Repair open,
Half=124.4Ω bad connection
Full=19.3Ω or short in CKT
673, 675, or 58.
®
No
Go to step 2.
Repair open,
bad connection
or short in
CKT30 between
fuel gauge and
fuse 4B.
Replace gauge.
Repair open or
bad connection
in CKT29
between fuel
gauge and fuel
selector valve?
Go to step 7.
Go to step 7.
Replace send-
ing unit.