Hummer H1 Service Manual page 1176

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DTC P1635 PCM 5 Volt Reference Low
5 VOLT
REFERNCE
CKP
SENSOR
SIGNAL
A
C5-B9
C29-A5
CKP
SENSOR
SIGNAL
Circuit Description
The PCM provides a 5 volt supply for use in powering up sen-
sors. This test monitors the voltage present at terminals BRD13
(shared by Boost and Crankshaft Position sensors) and BRD14
(Optical/Fuel temperature sensor (Cam/HI Res)). This is a type
B DTC.
Conditions for Setting the DTC
5 volt reference is less than 1 volt.
Action Taken When the DTC Sets
• Backup fuel.
• No EGR.
• No turbo boost.
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
C
CRANK
SHAFT
POSITION
SENSOR
(CKP)
SENSOR
GROUND
B
B
C5-B5 C5-B12
C27-C1 C27-D13 C27-C14
SENSOR 5 VOLT BOOST
GROUND REFERENCE SENSOR
SIGNAL
PCM/Tech 1 Scan Tool 111
C
BOOST/
BARO
PRESSURE
SENSOR
A
C5-B10
359 BK
C5-C5
C5-B11
TO
TFT
SENSOR
C29-B12
SENSOR IAT
GROUND SENSOR
SIGNAL
Diagnostic Aids
During the time the failure is present, the setting of additional
DTCs that share a 5 volt reference may also set.
Test Description
Number(s) below refer to the number(s) on the diagnostic ta-
ble.
1. Checks to confirm that a DTC is still present.
2. Checks to determine if there is a 5 volt reference from the
PCM.
3. Checks to determine if there is a short-to-ground in CKT
350 or CKT 375, or a short-to-ground in the PCM.
INTAKE AIR
A
TEMPERATURE
SENSOR (IAT)
A
ENGINE
COOLANT
B
TEMP
SENSOR
(ECT)
B
C5-C4
ECT
POWERTRAIN
SENSOR
CONTROL
SIGNAL
MODULE
9-S12-066