Hummer H1 Service Manual page 1160

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DTC P0571 Cruise Brake Switch Circuit
HOT AT
ALL TIMES
FUSE 4D
15 AMP
INTERIOR
A
STOP LAMP
SWITCH
B
31
C1
TO
STOP
LAMPS
STOP TCC/ CRUISE
LAMP BRAKE SIGNAL
SIGNAL
Circuit Description
The TCC normally closed brake switch supplies a B+ signal on
CKT 810 to the PCM. The circuit is opened when the brakes
are applied. The stop lamp/cruise control normally open brake
switch supplies a B+ signal on CKT 22 to the PCM when the
brake is applied. This is a type D DTC.
Conditions for Setting the DTC
• Switches disagree for 10 consecutive minutes.
or
• TCC and cruise control brake switches are not toggling
"open" and "closed" during 6 brake applications on
same ignition cycle.
Action Taken When the DTC Sets
Fourth gear operation in hot mode, and cruise control opera-
tion.
Conditions for Clearing the MIL/DTC
• 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.
05745159
HOT IN RUN
AND START
FUSE 6B
5 AMP
INTERIOR
D
A/C COMPRESSOR
CLUTCH RELAY
TCC CRUISE
BRAKE SWITCH EXTERIOR
FUSE
C
BOX
C5-8
40
A/C
DIODE
COMPRESSOR
CLUTCH
G1
PCM/Tech 1 Scan Tool 95
HOT IN RUN
AND START
A/C
FUSE 2C
REQUEST
10 AMP
SIGNAL
INTERIOR
HVAC
UNIT
C1-1
30 85
TEMPERATURE
CUTOUT
SWITCH
87 86
COMPRESSOR
HIGH
PRESSURE
CUTOUT
SWITCH
C28-D5
A/C COMPRESSOR
ENABLE
RELAY CONTROL
Diagnostic Aids
Refer to PCM Intermittent Diagnostic Trouble Codes or Per-
formance. Check customer driving habits and/or unusual traf-
fic conditions (i.e. stop and go, expressway traffic).
Test Description
Number(s) below refer to the number(s) on the diagnostic ta-
ble.
3. This test simulates brake switch closed or brakes "OFF".
4. This test checks the feed circuit.
HVAC
CONTROL
MODULE
H
C6-J8
AMBIENT
TEMP
CUTOUT
SWITCH
C1-39
C4-2
LOW
PRESSURE
CUTOUT
SWITCH
C4-5
C27-C2
A/C
REQUEST
SIGNAL
9-S12-054