Hummer H1 Service Manual page 1173

108 PCM/Tech 1 Scan Tool
DTC P1218 Injection Pump Calibration
Circuit
C9-J
WATER IN
FUEL LIGHT
DRAIN
LEFT HAND
FILTER
STATUS CENTER
C9-D
C3-F4
C1-45
B
9-S12-056
Circuit Description
The PCM uses a calibrated resistor mounted internally in the
injection pump to determine fuel rates. The resistor value is
stored in the PCM memory. If the PCM memory has been dis-
turbed or the PCM has been replaced, the PCM will relearn the
resistor value on the next ignition cycle. This is a type B DTC.
Conditions for Setting the DTC
• PCM currently does not have a valid resistor valve.
• PCM is unable to read a resistor value.
Action Taken When the DTC Sets
The lowest fuel table. Possible poor performance problem.
___________________________________________________
30 GY
HOT IN RUN
AND START
C3-N7
FUSE 4B FUSE 3B
5AMP 20AMP
INTERIOR EXTERIOR
FUSE BOX FUSE BOX
TO
IGNITION
SWITCH
291 PK
A
C
WATER IN
FUEL
SENSOR
C
A
POWER
CONTROL
MODULE
G2
HOT IN RUN
AND START
FUSE 3A
20AMP
EXTERIOR
FUSE BOX
C5-A4
239 PK
A
ENGINE
SHUTOFF
SOLENOID
A
FUEL
FUEL
SOLENOID
HEATER
DRIVER
C28-C15 C28-D3
ESO
FUEL INJECT
SOLENOID
CONTROL
CONTROL
Conditions for Clearing the MIL/DTC
• The PCM will turn the MIL off after three consecutive
trips without a fault condition.
• A History DTC will clear when forty consecutive
warm-up cycles that the diagnostic does not fail (coolant
temperature has risen 5°C (40°F) from start up coolant
temperature and engine coolant temperature exceeds
71°C (160°F) that same ignition cycle).
• Use of a scan.
Diagnostic Aids
Check connection at fuel injector driver. Clear DTC, and cycle
ignition. If DTC clears, treat condition as intermittent.
Test Description
Number(s) below refer to the number(s) on the diagnostic ta-
ble.
3. This step will determine if there is a problem with the con-
nection at the fuel solenoid driver or faulty injection pump.
FUEL
SOLENOID
D B
IGN FUEL FUEL
SOLENOID SOLENOID
HIGH LOW
FUEL
CLOSURE CLOSURE
SOLENOID
SIGNAL GROUND
CONTROL
A
E
C28-C3 C27-C13
CLOSURE CLOSURE
SIGNAL GROUND
®
A
B
F
C
C29-A1