Hummer H1 Service Manual page 1133

68 PCM/Tech 1 Scan Tool
DTC P0236 Turbocharger (TC) Boost System
C
CRANK
5 VOLT
SHAFT
REFERNCE
POSITION
SENSOR
(CKP)
CKP
SENSOR SENSOR
SIGNAL GROUND
A B
B
C5-B5 C5-B12
C5-B9
C29-A5 C27-C1 C27-D13 C27-C14
CKP SENSOR 5 VOLT BOOST
SENSOR GROUND REFERENCE SENSOR
SIGNAL SIGNAL
Circuit Description
The PCM operates a solenoid to control boost. This solenoid is
normally open. By providing a ground path the PCM energizes
the solenoid which then allows vacuum to pass to the waste-
gate valve. During normal operation, the PCM compares its
wastegate duty cycle signal with the boost signal and makes
corrections in the duty cycle accordingly. This is a type B
DTC.
Conditions for Setting the DTC
• Engine speed greater than 2400 RPM.
• Fuel rate greater than 20 mm.
• Boost pressure less than or equal to 20 kPa from desired
(internal to PCM).
• Conditions met for 10 seconds.
or
• Engine speed greater than 1800 but less than 2400 RPM.
• Fuel rate greater than 20 mm.
• Boost pressure less than or equal to (110 kPa) - ((100
kPa - Baro)/2) (internal to PCM).
• Conditions met for 2 seconds.
Action Taken When the DTC Sets
• Poor performance.
• Reduce maximum fuel.
• No TCC.
_____________________________________________________
C
INTAKE AIR
BOOST/
A
BARO TEMPERATURE
PRESSURE SENSOR (IAT)
SENSOR
A
A
B
C5-B10
B
359 BK
C5-C5 C5-C4
C5-B11
TO
TFT
SENSOR
C29-B12
SENSOR IAT ECT
GROUND SENSOR SENSOR
SIGNAL SIGNAL
ACCELERATIOR
PEDAL POSITION
SENSOR
D
2
G
1
ENGINE
E
COOLANT
TEMP
SENSOR
(ECT)
3
HOT IN RUN
AND START
FUSE 3A
10 AMP
EXTERIOR
POWERTRAIN
CONTROL
MODULE
RESUME
ACCEL
HOT IN RUN
AND START
9-S12-066
SET
COAST
FUSE 5C
10AMP
INTERIOR B
295 BR
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
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
A vacuum leak or a pinched vacuum line may cause a DTC
P0236. Check all vacuum lines and components connected to
the hoses for leaks or sharp bends. Check vacuum source. A
possible EGR DTC will store if there is a problem with the
vacuum source. Also check for proper vacuum line routing.
This diagnostic checks for a "skewed" sensor.
Test Description
Number(s) below refer to the number(s) on the diagnostic ta-
ble.
This will check the Boost sensor scaling. One step will check
the scaling with vacuum applied and one without.
44
B
722 PP
32
C
721 LB
53
A
719 BR
17
F
718 DB
60
J
725 GY
15
K
724 DG
14
723 YL
20
717 WH
22
720 TN
C1
C5-A4
A B
154 TN
C
YL 153 LG
D
GRN 152 DB
A
RD 151 GY
ON/
OFF
®
POWERTRAIN
CONTROL
MODULE
(PCM)
C29-A12
GROUND
C27-C5 APP 2
SIGNAL
C29-B1
GROUND
C29-B2
APP 1
SIGNAL
C27-D6
GROUND
C27-D4 APP 3
SIGNAL
C27-D3
C27-D12
5 VOLT
REFERENCE
C28-C2
C5-D3
WASTEGATE
C28-D14
SOLENOID
CONTROL
37
C27-D10 RESUME
ACCEL
SIGNAL
42
SET
C29-B11
COAST
SIGNAL
29
C29-A11
ON / OFF
SIGNAL
C1
9-S12-055