Isuzu engine C22NE / 22LE / 20LE. Manual — part 75
DRIVEABILITY AND EMISSIONS 6E1-129
0.5
R
0.5
G
0.5
GR
0.5
RED
0.75
GRN
0.75
L
0.5
GRN
Engine
Control
Module
(ECM)
F14
B1
A3
5 Volt
Reference
Signal
Throttle
Position
(TP)
Sensor
Input
Sensor
Ground
Sensor
Ground
B7
B2
Throttle
Position
(TP)
Sensor
B C
A
Manifold
Absolute
Pressure
Sensor
Engine
Coolant
Temperature
Sensor
B8
LO
HI
OUT
0.5
L/R
THROTTLE POSITION (TP) SENSOR CIRCUIT RANGE/PERFORMANCE
PROBLEM
Circuit Description
The throttle position (TP) sensor circuit provides a
voltage signal that changes relative to throttle blade
angle. The signal voltage will vary from about 0.25
volts at closed throttle to about 4.75 volts at wide open
throttle (WOT).
The Throttle Position (TP) signal is used by the engine
control module (ECM) for fuel control and most of the
ECM-controlled outputs. The ECM monitors throttle
position and compares actual throttle positions from
the TP sensor to a predicted TP value calculated from
engine speed.
Diagnostic Aids
Check for the following conditions:
• Skewed MAP signal or faulty MAP sensor-An
incorrect MAP signal may cause the ECM to
incorrectly calculate the predicted TP sensor value
during high engine load situations. Check for an
unusually low MAP reading.
• Poor connection at ECM-Inspect harness
connectors for backed-out terminals, improper
mating, broken lock, improperly formed or damaged
terminals, and poor terminal-to-wire connection.
• Damaged Harness-Inspect the wiring harness for
damage: An open Circuit, shorts to Ground, or
shorts to Battery Positive. If the harness appears to
be OK, observe the TP display on the Scan Tool
while moving connectors and wiring harnesses
related to the sensor. A change in the display will
indicate the location of the fault.
6E1-130 DRIVEABILITY AND EMISSIONS
TP Sensor Circuit Range/Performance Problem
Step
Action
Value(s)
Yes
No
1
Was the "On-Board Diagnostic (OBD) System Check "
performed?
-
Go to Step 2
Go to OBD
System
Check
2
1. Ignition ON, engine OFF.
2. Monitor the TP value on the Scan Tool While moving
the throttle between 0% and 100%.
Does the TP value on the Scan Tool move smoothly from
0% (0.25 volts) to 100% (4.75 volts)?
-
Go to Step 3
Go to Step 10
3
1. Ignition OFF.
2. Disconnect the Throttle Position (TP) Sensor electrical
connector, located on the RH side of the Throttle body.
3. Start the engine, and monitor the TP value with the
Scan Tool.
Does the TP value on the Scan Tool hold steadily within
the given range?
0-0.25 volts
0%
Go to Step 5
Go to Step 4
4
Check the TP sensor signal circuit, between the TP
sensor and the Engine Control Module (ECM), for a short
to voltage.
Was the problem found?
-
Verify Repair
Go to Step 11
5
Check the TP sensor signal circuit, between the TP
sensor and the ECM, the following conditions:
• A short to ground
• An open circuit
Was the problem found?
-
Verify Repair
Go to Step 6
6
Check the 5 Volt signal circuit between the TP sensor and
the ECM, for the following conditions:
• An Open Circuit
• A short to ground
• A short to voltage
Was the problem found?
-
Verify Repair
Go to Step 7
7
1. Ignition OFF.
2. Place a fused jumper between the TP sensor circuit
and the 5 volt signal circuit both at the wiring harness
TP sensor connector.
3. Ignition ON, engine OFF.
4. Observe the TP value displayed on the Scan Tool.
Does the Scan Tool read the following value?
about 5 volts
100%
Go to Step 8
Go to Step 11
8
Check the TP sensor ground circuit, between the TP
sensor and the ECM, for the following conditions:
• An Open Circuit
• A short to ground
• A short to voltage
Was the problem found?
-
Verify Repair
Go to Step 9
DRIVEABILITY AND EMISSIONS 6E1-131
TP Sensor Circuit Range/Performance Problem (Cont'd)
Step
Action
Value(s)
Yes
No
9
1. Ignition OFF.
2. Place a Digital Multimeter (DVM), set to measure
voltage between the ground circuit and the 5 volt signal
circuit, both at the wiring harness' TP sensor
connector.
3. Ignition ON, engine OFF.
Does the DVM indicate the following value?
about 5 volts
Go to Step 10
Go to Step 11
10
Replace the TP sensor.
Verify repair.
-
-
-
11
Replace the EPROM or ECM.
Note) Refer to 6E1-243.
-
-
-
6E1-132 DRIVEABILITY AND EMISSIONS
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