Hummer H1 Service Manual page 272

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DTC P0723 Output Speed Sensor Intermittent
570 BK
8
GROUND
G2
Circuit Description
The speed sensor circuit consists of a magnetic induction type
sensor, which is the Output Shaft Speed (OSS) Sensor, a Vehi-
cle Speed Sensor (VSS) Buffer Module, and wiring. Gear teeth
pressed onto the output shaft carrier assembly induce an alter-
nating voltage into the sensor. This signal transmits to the VSS
Buffer Module. The VSS Buffer Module compensates for vari-
ous final drive ratios. The VSS Buffer Module also converts
the alternating current (AC) OSS signal into a 40 pulse per rev-
olution (PPR) 5 volt DC square wave form signal on circuit
437 to indicate transmission output speed.
If the PCM detects an unrealistically large change in the Out-
put Shaft Speed (OSS) Sensor reading, then DTC P0723 sets.
DTC P0723 is a type A DTC.
05745159
HOT IN
RUN AND START
FUSE
3A
20A
EXTERIOR
POWERTRAIN
CONTROL
MODULE
(PCM)
VEHICLE
SPEED
SENSOR
(VSS)
A B
TWISTED
PAIR
A B
C33
9 13 7
IGNITION VEHICLE SPEED
POSITIVE SENSOR SIGNAL
VOLTAGE
Transmission/Transfer Case
SPEEDO
A/T OUTPUT BUFFERED
SPEED SENSOR VSS
SIGNAL (VSS) SIGNAL
C29-A3 C29-A6
14 4
VSS BUFFERED
SIGNAL SPEED
OUTPUT SENSOR
SIGNAL
Conditions for Setting the DTC
• No 4WD Low DTC P1875.
• No TFP Val. Position Sw. assembly change for greater
than 7 seconds.
• The engine must be running more than 475 RPM for at
least 7 second.
• The OSS RPM decrease is greater than 1000 RPM while
in a Drive gear for at least 4 seconds.
• The PCM sets the Malfunction Indicator Lamp (MIL).
Action Taken When the DTC Sets
• The PCM defaults to maximum line pressure.
• The PCM freezes shift adapts.
• The PCM defaults to the calculated output speed value
using the ISS Sensor values.
C3-P9
C1-18
11
SPEEDO
SIGNAL
VEHICLE
SPEED
SENSOR
BUFFER
(DRAC)
9-S12-068
5-73