Hummer H1 Service Manual page 1117

52 PCM/Tech 1 Scan Tool
DTC P0221 Accelerator Pedal Position (APP)
Sensor 2 Circuit Performance
Circuit Description
The Accelerator Pedal Position (APP) module provides a volt-
age signal that changes relative to accelerator position. There
are three sensors located within the APP module that are scaled
differently. This is a type C DTC.
Conditions for Setting the DTC
• Ignition voltage is greater than 6.4 volts.
• Engine speed greater than 300 rpm.
• The difference between APP 2 and APP 1 is greater than
.23 volts (PCM compares pre-scaled voltage (internal to
PCM)).
• The difference between APP 2 and APP 3 is greater than
.50 volts (PCM compares pre-scaled voltage (internal to
PCM)).
• No in range faults for APP 1 or APP 3 (PCM checks for
high and low voltage faults).
• Conditions met for 2 seconds.
Action Taken When the DTC Sets
• The input from APP 2 sensor is ignored.
• A current and history DTC will set but it will not turn on
the "Service Throttle Soon" lamp.
• The throttle will operate normally as long as there is
only one malfunction present. If there are two APP mal-
functions present, the PCM will then turn "ON" the
"Service Throttle Soon" lamp and limit power. If a third
_____________________________________________________
ACCELERATIOR
PEDAL POSITION
SENSOR
44
D B
32
C
2
53
G A
17
F
1
60
E J
15
K
3
14
20
HOT IN RUN
22
AND START
C1
FUSE 3A
10 AMP
EXTERIOR
C5-A4
A
RESUME
ACCEL
HOT IN RUN
AND START
GRN
SET
COAST
FUSE 5C
10AMP
INTERIOR B
ON/
295 BR OFF
POWERTRAIN
CONTROL
MODULE
(PCM)
722 PP C29-A12
GROUND
721 LB C27-C5 APP 2
SIGNAL
719 BR C29-B1
GROUND
718 DB C29-B2
APP 1
SIGNAL
725 GY C27-D6
GROUND
724 DG C27-D4 APP 3
SIGNAL
723 YL C27-D3
717 WH C27-D12
5 VOLT
REFERENCE
720 TN C28-C2
C5-D3
WASTEGATE
B
154 TN C28-D14
SOLENOID
CONTROL
C
37
C27-D10 RESUME
YL 153 LG
ACCEL
SIGNAL
D
42
SET
C29-B11
152 DB
COAST
SIGNAL
A 29
RD 151 GY C29-A11
ON / OFF
SIGNAL
C1
9-S12-055
APP malfunction is present, the "Service Throttle Soon"
lamp will be "ON" and will only allow the engine to op-
erate at idle.
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 Tool
Diagnostic Aids
A scan tool reads APP 2 position in volts and should read about
4.5 volts with throttle closed and ignition "ON" or at idle. Volt-
age should decrease at a steady rate as throttle is moved toward
Wide Open Throttle (WOT). Also, 90% pedal travel is accept-
able for correct APP operation. Refer to Section 2 for "Inter-
mittents". Scan APP 2 sensor while depressing accelerator
pedal with engine stopped and ignition "ON". Display should
vary from about 4.5 volts when throttle was closed to about 1.5
volts when throttle is held at Wide Open Throttle (WOT) posi-
tion.
Test Description
Number(s) below refer to the number(s) on the diagnostic ta-
ble.
4. This step determines if there is a good 5 volt reference.
5. This step will check for an open in the ground circuit.
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