Hummer H1 Service Manual page 1135

70 PCM/Tech 1 Scan Tool
DTC P0237 Turbocharger (TC) Boost Sensor
Circuit Low Voltage
C
5 VOLT
REFERNCE
CKP
SENSOR
SIGNAL
A
C5
B9
C29-A5 C29-B12
CKP
SENSOR
SIGNAL
Circuit Description
The PCM sends a 5 volt reference signal to the boost sensor.
As manifold pressure changes, the electrical resistance of the
boost sensor also changes. By monitoring the sensor output
voltage, the PCM detects how much pressure is being pro-
duced by the turbocharger in the intake manifold. The PCM
uses the boost sensor to control turbo boost and fuel at different
loads. This is a type B DTC.
Conditions for Setting the DTC
• Boost pressure less than 40 kPa.
• Conditions met for 2 seconds.
Action Taken When the DTC Sets
No turbo boost.
Conditions for Clearing the MIL/DTC
• The PCM will turn the MIL off after three consecutive
trips without a fault condition.
• A History DTC will clear when forty consecutive
warm-up cycles that the diagnostic does not fail (coolant
4-1-00
_____________________________________________________
CRANK
SHAFT
POSITION
SENSOR
(CKP)
SENSOR
GROUND
B
B11 B12
C27-D13 C27-C14
SENSOR 5 VOLT BOOST
GROUND REFERENCE SENSOR
SIGNAL
C
BOOST/
BARO
PRESSURE
SENSOR
B A
651 BK
B10 C4
C27-C11 C27-C1
ECT
SENSOR
SIGNAL
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 Tool.
Diagnostic Aids
With the ignition "ON" and the engine stopped, boost pressure
is equal to atmospheric pressure. Comparison of this reading
with known good vehicle using the same sensor is a good way
to check accuracy of a "suspect" sensor. Readings should be
the same +.4 volt. Very little boost can be attained by revving
the engine in neutral. If the Boost sensor signal circuit is open
or shorted to ground, Boost solenoid will show a zero duty cy-
cle. A J–39200 can be used to measure (actual) signal voltage
at the PCM harness connector.
Test Description
Number(s) below refer to the number(s) on the diagnostic table.
2. This step will determine if DTC P0237 is the result of a hard
failure or an intermittent condition.
3. This step simulates conditions for a DTC P0237. If the PCM
recognizes the change, the PCM and signal circuit are OK.
ENGINE
A
COOLANT
TEMP
SENSOR
(ECT)
INTAKE AIR
TEMPERATURE
SENSOR (IAT)
A
B
B
C5
B5
C27-C4
SENSOR IAT
POWERTRAIN
GROUND SENSOR
CONTROL
SIGNAL
MODULE
9-S12-066
®