Hummer H1 Service Manual page 277

5-78 Transmission/Transfer Case
DTC P0724 Brake Switch Circuit High Input
HOT AT
ALL TIMES
FUSE 4D
INTERIOR
A
STOP LAMP
SWITCH
B
31
C1
TO
STOP
LAMPS
STOP
LAMP
SIGNAL
Circuit Description
The brake switch indicates brake pedal position. The normally-
closed brake switch supplies a B+ signal on circuit 810 to the
PCM. The signal voltage circuit is opened when the brakes are
applied. The PCM uses this signal to deenergize the converter
clutch solenoid when the brakes are applied.
This DTC detects a closed brake switch during decelerations.
Conditions For Setting DTC
• No DTC P0722, P0723.
• The PCM detects a closed brake switch/circuit (12
volts) for 2 seconds during decelerations and the follow-
ing events occur seven consecutive times: vehicle speed
is greater than 32 km/h (20 mph) for 6 seconds; then ve-
hicle speed is between 8 and 32 km/h (5 and 20 mph) for
4 seconds; then vehicle speed is less than 8 km/h (5
mph).
• All conditions exist with 7 occurrences.
Action Taken When The DTC Sets
• PCM disregards the brake switch state if TPS is greater
than 12% and vehicle speed is greater than 45 mph.
• The PCM will NOT illuminate the warning lamp.
HOT IN RUN
AND START
FUSE 6B
15 AMP 5 AMP
INTERIOR
D
A/C COMPRESSOR
CLUTCH RELAY
TCC CRUISE
BRAKE SWITCH
EXTERIOR
C
C5-8
40
DIODE
TCC/ CRUISE
BRAKE SIGNAL
_____________________________________________
HOT IN RUN
AND START
FUSE 2C
10 AMP
INTERIOR
C1-1
30 85
TEMPERATURE
FUSE
BOX
87 86
COMPRESSOR
A/C
COMPRESSOR
CLUTCH
PRESSURE
CUTOUT
SWITCH
G1
C28-D5
A/C COMPRESSOR
ENABLE
RELAY CONTROL
Conditions For Clearing The DTC
• The DTC can be cleared using a scan tool. The DTC
will be cleared when the vehicle has achieved 40 warm-
up cycles without a failure reported.
• The PCM will cancel the DTC default actions when the
fault no longer exists and the ignition is cycled "off"
long enough to power down the PCM.
Diagnostic Aids
• Inspect the wiring for poor electrical connections at the
PCM and brake switch. Look for bent, backed out, de-
formed or damaged terminals. Check for weak terminal
tension as well. Also check for a chafed wire that could
short to bare metal or other wiring. Inspect for a broken
wire inside the insulation.
• When diagnosing for a possible intermittent short or
open condition, move the wiring harness while observ-
ing test equipment for a change.
• Check customer driving habits and/or unusual traffic
conditions (i.e. stop and go, expressway).
• Check brake switch for proper mounting and adjust-
ment.
• If any engine DTCs or TPS codes are present diagnose
and clear these DTCs first. Then check to see if the
transmission DTCs have reset.
CONTROL
MODULE
A/C
REQUEST
SIGNAL
H
C6-J8
HVAC
UNIT
CUTOUT
SWITCH
C1-39
C4-2
HIGH
C27-C2
A/C
REQUEST
SIGNAL
®
HVAC
AMBIENT
TEMP
CUTOUT
SWITCH
LOW
PRESSURE
CUTOUT
SWITCH
C4-5
9-S12-054