Hummer H1 Service Manual page 1154

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DTC P0501 Vehicle Speed Sensor Circuit
POWERTRAIN
CONTROL
MODULE
( PCM )
GROUND
GROUND
40 PULSE
OUTPUT SHAFT
REVOLUTION
4000 PPM
CONTROL
REFERENCE
Circuit Description
The speed sensor circuit consists of a magnetic induction type
sensor, a Digital Ratio Adaptor (DRA) and wiring. Geared
teeth pressed on the output shaft induce an alternating current
in the sensor. This A/C signal is transmitted to the DRA. The
DRA compensates for various axle ratios and converts the sig-
nal into a digital signal for use by the speedometer, cruise con-
trol, and the PCM. The DRA sends two different signal to the
PCM. Circuit 565 sends a signal of 40 pulses per revolution of
the output shaft to the PCM. This signal is used to control shift
points, line pressure, TCC and diagnostic codes. Circuit 223
sends a signal of 4000 pulses per mile to the PCM. This signal
is used to control engine operating functions, cruise control
and DTCs.When DTC P0501 or P0723 is set, second gear only at
a maximum line pressure will occur. This is a type D DTC.
Conditions for Setting the DTC
• Vehicle speed greater than 20 m.p.h.
• Four wheel low not selected.
• VSS buffer calculated speed is less than half the trans-
mission calculated speed.
• VSS buffer calculated speed is greater than transmission
calculated speed by 20 m.p.h.
05745159
VEHICLE
SPEED
SENSOR
(VSS)
G2
C29
570 BK
A6
570 BK
A7
C28
565 BR
D6
SIGNAL
TO PCM
CRUISE
D9
SIGNAL
4 7
CRUISE VEHICLE
CONTROL SPEED
REFERENCE SENSOR
SIGNAL RETURN
4000 PPM
IGNITION
B A
TWISTED
PAIR
C33
B A
8 9 12
GROUND +12 VOLT VEHICLE
IGNITION SPEED
SIGNAL
DIGITAL RATIO ADAPTER
• All conditions met for 2 seconds.
Action Taken When the DTC Sets
No cruise control.
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.
Diagnostic Aids
Check connections at VSS buffer and PCM. Refer to
4L80EDiagnostic Diagnostic Trouble Codes, Section 10 if
DTC P0722 or DTC P0723 is also set.
Test Description
Number(s) below refer to the number(s) on the diagnostic table.
3. This tests for B+ at VSS buffer.
4. This tests for proper ground path for vehicle speed sensor
signal buffer.
PCM/Tech 1 Scan Tool 89
TO TO
SPEEDO
FUSE
1D
15 AMP
EXTERIOR
FUSE
BOX
C3-P9
C1-18
13 10
OUTPUT SHAFT SPEEDO
REVOLUTION REFERENCE
SIGNAL SIGNAL
00-S12-038
3-1-01