Isuzu engine C22NE / 22LE / 20LE. Manual — part 90
DRIVEABILITY AND EMISSIONS 6E1-189
DTC (Flash DTC = 71)
Intake Air Temperature (IAT) Sensor Too Low (Cont'd)
Step
Action
Value(s)
Yes
No
4
1. Ignition OFF.
2. Disconnect the IAT sensor electrical connector.
3. Ignition ON.
4. Observe the intake air temperature on the Scan Tool.
Is the intake air temperature below the specified value?
−36°C
(
−32.8°F)
Go to Step 6
Go to Step 5
5
1. Ignition OFF.
2. Disconnect the PCM electrical connectors.
3. Check the IAT sensor signal circuit for a short to
ground.
Is the IAT sensor signal circuit shorted to ground?
-
Verify repair
Go to Step 7
6
Replace the IAT sensor.
Is the action complete?
-
Verify repair
-
7
Replace the EPROM or ECM.
Note) Refer to 6E1-243.
Is the action complete?
-
Verify repair
-
6E1-190 DRIVEABILITY AND EMISSIONS
DRIVEABILITY AND EMISSIONS 6E1-191
ECM
Fuse
15A
Engine
Fuse
15A
Canister
Purge
Solenoid
1.25
R/W
0.85G/W
2B/R
0.85G/R
0.85G/B
0.85G
1.25
R/W
0.85
L/Y
Injector
Fuse
20A
Fuel
Pump
A4
A6
A8
A9
A7
A5
E16
Fuel
Injector
Control
#4
A
B
#3
A
B
#2
A
B
#1
A
B
Engine
Control
Module
(ECM)
HOT AT ALL TIMES
HOT IN RUN AND START
DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 17)
INJECTOR CIRCUIT MALFUNCTION
Circuit Description
The engine control module (ECM) has 2 injector driver
circuits. Each controls 2 injectors as a one group.
When a driver circuit is grounded by the ECM, the
injector is activated. The ECM monitors the current in
each driver circuit. The ECM measures a voltage drop
through a fixed resistor and controls it. The voltage on
each driver is monitored to detect a fault. If the voltage
is not what the ECM expects to monitor on the circuit,
a Diagnostic Trouble Code is set. This Diagnostic
Trouble Code is also set if an injector driver is shorted
to voltage. This code an injectors short to ground,
battery or a disconnected injector, then a DTC 17 will
be set.
Conditions for Setting the DTC
• The actual output voltage of injector driver is
opposite to the expected state thus setting injector
feedback line low.
• Fuel pump relay is commanded on and Fuel pump
relay is not shorted to bettery and battery voltage is
greater than 9 volts.
Action Taken When the DTC Sets
• The ECM will illuminate the malfunction indicator
lamp (MIL).
• "Open Loop" fuel control will be in effect.
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.
Diagnostic Aids
An injector driver circuit that is open or shorted to
voltage will cause a Diagnostic Trouble Code 17 to
6E1-192 DRIVEABILITY AND EMISSIONS
set. It will also cause a misfire due to an inoperative
injector.
Long term and short term fuel trims that are
excessively high or low are a good indication that an
injector is faulty. Use Fuel Injector Coil Test Procedure
to check for faulty injectors.
Test Description
The number(s) below refer to the step number(s) on
the Diagnostic Chart.
3. This step determines if Diagnostic Trouble Code 17
is the result of a hard failure or an intermittent
condition.
4. This steps tests the harness wiring and ECM
control of the injectors.
6. Because the test light was ON steady, voltage to
the injector is OK, but the driver circuit is grounded
at all times. This step determines if the circuit is
shorted to ground or the ECM is faulty.
8. Because the test light was OFF steady, the injector
driver circuit is shorted to voltage.
10.Normal injector resistance is slightly more than if
tested directly at the injector because it includes
resistance of the harness wires. The normal value
is about 13.5
Ω.
DTC (Flash DTC = 17)
Injector Circuit Malfunction
(Repeat Following Steps for each injector if necessary)
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
Will the engine start?
-
Go to Step 3
Cranks But
Will Not Run
Chart
3
1. Install the Scan Tool.
2. Idle the engine for one minute.
Does the Diagnostic Trouble Code 17 Set?
-
Go to Step 4
Go to
Diagnostic
Aids
4
1. Ignition off.
2. Disconnect the injector connector of No.1 Cyl. And then
start the engine to check the injector working condition.
3. Repeat above steps on all injectors.
4. If the injector and injector driver circuit is normal
condition, the engine becomes rough running.
Does the engine running condition change?
-
Go to OBD
System
Check
Go to Step 5
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