Isuzu KB P190. Service manual — part 578
6E–142
ENGINE DRIVEABILITY AND EMISSIONS
11
Using the DVM and check the ECT sensor ground
circuit.
Breaker box is available:
1. Ignition “Off”, engine “Off”.
2. Install the breaker box as type A. (ECM
disconnected) Refer to 6E-88 page.
3. Disconnect the ECT sensor connector.
4. Check the circuit for open circuit.
Was the problem found?
Breaker box is not available:
1. Ignition “Off”, engine “Off”.
2. Disconnect the ECT sensor connector.
3. Check the circuit for open circuit.
Was the problem found?
—
Repair faulty
harness and
verify repair
Go to Step 14
12
Substitute a known good ECT sensor assembly and
recheck.
Was the problem solved?
—
Go to Step 13
Go to Step 14
13
Replace the ECT sensor.
Is the action complete?
—
Verify repair
—
14
Is the ECM programmed with the latest software
release?
If not, download the latest software to the ECM using
the “SPS (Service Programming System)”.
Was the problem solved?
—
Verify repair
Go to Step 15
15
Replace the ECM.
Is the action complete?
IMPORTANT: The replacement ECM must be
programmed. Refer to section of the Service
Programming System (SPS) in this manual.
Following ECM programming, the immobilizer system
(if equipped) must be linked to the ECM. Refer to
section 11 “Immobilizer System-ECM replacement” for
the ECM/Immobilizer linking procedure.
—
Verify repair
—
Step
Action
Value(s)
Yes
No
J1-32
Breaker Box
Ω
E-69
2
2
32
E60(J1)
E69
ENGINE DRIVEABILITY AND EMISSIONS
6E–143
DIAGNOSTIC TROUBLE CODE (DTC) P0122 THROTTLE POSITION SENSOR
LOW INPUT
Condition for setting the DTC and action taken when the DTC sets
Circuit Description
The throttle position sensor circuit provides a signal
voltage 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 TPS signal is used by the engine control module
(ECM) for fuel control and most of the ECM-controlled
outputs. If the ECM detect a continuous short to ground
in the TPS or circuit, then a code P0122 will set.
Diagnostic Aids
• 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, short to ground, short to battery positive,
and open circuit. If the harness appears to be OK,
observe the throttle position display on the Tech 2
while moving connectors and wiring harnesses
related to the TPS. A change in the display will
indicate the location of the fault.
Code
Type
DTC Name
DTC Setting Condition
Fail-Safe (Back Up)
P0122
A
Throttle Position Sensor Low Input
TPS output voltage is below 0.14V.
The ECM uses 0% condition as substitute.
6E–144
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0122 Throttle Position Sensor Low Input
Step
Action
Value(s)
Yes
No
1
Was the “On-Board Diagnostic (OBD) System Check”
performed?
—
Go to Step 2
Go to On Board
Diagnostic
(OBD) System
Check
2
1. Connect the Tech 2.
2. Review and record the failure information.
3. Select “F0: Read DTC Infor By Priority” in “F0:
Diagnostic Trouble Code”.
Is the DTC P0122 stored as “Present Failure”?
—
Go to Step 3
Refer to
Diagnostic Aids
and Go to Step
3
3
1. Using the Tech2, ignition “On” and engine “Off”.
2. Select “Clear DTC Information” with the Tech2 and
clear the DTC information.
3. Operate the vehicle and monitor the “F5: Failed
This Ignition” in “F2: DTC Information”.
Was the DTC P0122 stored in this ignition cycle?
—
Go to Step 4
Refer to
Diagnostic Aids
and Go to Step
4
4
Check for poor/faulty connection at the TPS or ECM
connector. If a poor/faulty connection is found, repair
as necessary.
Was the problem found?
—
Verify repair
Go to Step 5
5
Visually check the TPS.
Was the problem found?
—
Go to Step 10
Go to Step 6
6
Using the DVM and check the TPS.
1. Ignition “Off”, engine “Off”.
2. Disconnect TPS connector.
3. Measure the resistance of TPS.
Does the tester indicate standard resistance as shown
in the following table?
Standard
resistance
Go to Step 7
Go to Step 10
E60(J1)
E68
32
15 7
Measurement
Terminal
Resistance (
Ω)
1 - 2
Approximately 5.6k
Ω at idle position &
WOT
2 - 3
Approximately 6.0k
Ω at idle position
Approximately 1.7k
Ω at WOT
1 - 3
Approximately 2.3k
Ω at idle position &
WOT
Approximately 6.6k
Ω at WOT
2
1
3
TPS
ENGINE DRIVEABILITY AND EMISSIONS
6E–145
7
Using the DVM and check the TPS power supply
circuit.
1. Ignition “On”, engine “Off”.
2. Disconnect the TPS connector.
3. Check the circuit for open or short to ground
circuit.
Was the DVM indicated specified value?
Approximately
5.0V
Go to Step 9
Go to Step 8
8
Repair the open or short to ground circuit between the
ECM and TPS.
Was the problem solved?
—
Verify repair
Go to Step 12
Step
Action
Value(s)
Yes
No
V
E68
2
2
E60(J1)
E68
15
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