Isuzu engine C22NE / 22LE / 20LE. Manual — part 76
DRIVEABILITY AND EMISSIONS 6E1-133
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
DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 22)
THROTTLE POSITION (TP) SENSOR CIRCUIT LOW INPUT
Circuit Description
The throttle position (Throttle Position) sensor circuit
provides a voltage signal that changes relative to
throttle blade angle. The signal voltage will vary from
below 1 volt at closed throttle to about 4 volts at wide
open throttle (WOT).
The Throttle Position signal is used by the engine
control module (ECM) for fuel control and most of the
ECM-controlled outputs. If the ECM detects a low
inpedance short to ground in the Throttle Position
sensor or circuit, then a code 22 will set.
Conditions for Setting the DTC
• Throttle Position sensor signal voltage is less than
0.19 volt.
Action Taken When the DTC Sets
• The ECM will illuminate the malfunction indicator
lamp (MIL) the first time the fault is detected.
• The ECM will use a default throttle position based
on RPM.
Conditions for Clearing the MIL/DTC
Once the ECM determines that a fault(s) has been
rectified then the CEL will switch OFF, although the
fault code will remain in the ECM memory.
Any fault codes will remain in ECM memory until -
1. They are cleared by disconnecting the Battery for
more than 30 seconds.
2. A service tool such as Tech 2 is used to clear them.
3. Ten consecutive starts without logging a fault.
6E1-134 DRIVEABILITY AND EMISSIONS
Diagnostic Aids
Check for the following conditions:
• Poor connection at ECM - Inspect harness
connectors for backed-out terminals, improper
mating, broken locks, improperly formed or
damaged terminals, and poor terminal-to-wire
connection.
• Damaged harness - Inspect the wiring harness for
damage. If the harness appears to be OK, observe
the throttle position display on the Scan Tool while
moving connectors and wiring harnesses related to
the throttle Position sensor. A change in the display
will indicate the location of the fault.
DTC (Flash DTC = 22)
Throttle Position (TP) Sensor Circuit Low Input
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. With the throttle closed, observe the "Throttle Position
Sensor" display on the Scan Tool. is the "Throttle
Position Sensor" below the specified value?
0.19V
Go to Step 4
Go to Step 3
3
1. Ignition ON engine OFF.
2. Using a Scan Tool, monitor info for Diagnostic Trouble
Code 22.
Does the Scan Tool indicate Diagnostic Trouble Code 22
failed?
-
Go to Step 4
Refer to
Diagnostic
Aids
4
1. Ignition OFF.
2. Disconnect the Throttle Position sensor electrical
connector.
3. Jumper the 5 volt reference circuit and the Throttle
Position signal together at the Throttle Position sensor
harness connector.
4. Ignition ON.
Observe the "Throttle Position Sensor" value displayed
on the Scan Tool.
Is the "Throttle Position Sensor" at the specified value?
5V
Go to Step 10
Go to Step 5
5
1. Disconnect jumper.
2. Connect a test light between B+ and the Throttle
Position sensor signal circuit at the Throttle Position
sensor harness connector.
Observe the "Throttle Position Sensor" value displayed
on the Scan Tool.
Is the "Throttle Position Sensor" at the specified value?
5V
Go to Step 6
Go to Step 8
DRIVEABILITY AND EMISSIONS 6E1-135
DTC (Flash DTC = 22)
Throttle Position (TP) Sensor Circuit Low Input (Cont'd)
Step
Action
Value(s)
Yes
No
6
1. Ignition OFF.
2. Disconnect the ECM and check the 5 volt reference
circuit for an open or short to ground.
3. If the 5 volt reference circuit is open or shorted to
ground, repair it as necessary.
Was the 5 volt reference circuit open or shorted to
ground?
-
Verify repair
Go to Step 7
7
Check the 5 volt reference circuit for a poor connection at
the ECM and replace the terminal if necessary.
Did the terminal require replacement?
-
Verify repair
Go to Step 12
8
1. Ignition OFF.
2. Disconnect the ECM, and check the Throttle Position
signal circuit for an open, short to ground, or short to
the sensor ground circuit.
3. If the Throttle Position sensor signal circuit is open or
shorted to ground, repair it as necessary.
Was the Throttle Position signal circuit open or shorted to
ground?
-
Verify repair
Go to Step 9
9
Check the Throttle Position sensor signal circuit for a poor
connection at the ECM and replace the terminal if
necessary.
Did the terminal require replacement?
-
Verify repair
Go to Step 12
10
Check the Throttle Position sensor signal circuit for a poor
connection at the Throttle Position sensor and replace the
terminal if necessary.
Did the terminal require replacement?
-
Verify repair
Go to Step 11
11
Replace the Throttle Position sensor.
Is the action complete?
-
Verify repair
-
12
Replace the EPROM or ECM.
Is the action complete?
Note) Refer to 6E1-243.
-
Verify repair
-
6E1-136 DRIVEABILITY AND EMISSIONS
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