Isuzu engine C22NE / 22LE / 20LE. Service manual — part 94
DRIVEABILITY AND EMISSIONS 6E1-205
DTC (Flash DTC = 35)
Idle Air Control (IAC) Error
Step
Action
Value(s)
Yes
No
1
1. Ignition OFF..
2. Connect the IAC motor analyzer 5-8840-2312-0 to the
IAC valve.
3. Set the parking brake.
4. Block the wheels.
5. Turn the air conditioning OFF.
6. Idle the engine in Park (A/T) or Neutral (M/T).
7. Install the scan tool. Display the RPM.
8. Use the IAC motor analyzer 5-8840-2312-0 to extend
and retract the IAC valve.
9. The engine speed should decrease and increase as
the IAC is cycled.
Does the RPM change?
-
Go to Step 2
Go to Step 3
2
RPM should change smoothly with each flash of the IAC
motor analyzer 5-8840-2312-0 light.
Does the RPM change within the range specified?
700-1500
RPM
Go to Step 6
Go to Step 3
3
Check the IAC passages.
Are the IAC passages blocked?
-
Go to Step 4
Go to Step 5
4
Clear any obstruction from the IAC passages.
Is the action complete?
-
Verify repair
-
5
Replace the IAC. Refer to On-Vehicle Service, Idle Air
Control Valve.
Is the action complete?
-
Verify repair
-
6
1. Install the appropriate IAC noid light from 5-8840-2312-
0 into the powertrain control module harness.
2. Cycle the IAC motor analyzer 5-8840-2312-0 and
observe the noid lights.
3. Both the lights should cycle red and green, but never
OFF, as the RPM is changed over its range.
Do the noid lights cycle red and green?
-
Go to Step 7
Go to Step 8
7
1. Use the other connector on the IAC motor analyzer 5-
8840-2312-0 pigtail.
2. Check the resistance across the IAC coils.
Measure the resistance between terminal A and
terminal B.
3. Measure the resistance between terminal C and
terminal D.
Is the resistance within the specified range?
40-80 ohms
Go to Step 9
Go to Step 10
6E1-206 DRIVEABILITY AND EMISSIONS
DTC (Flash DTC = 35)
Idle Air Control (IAC) Error (Cont’d)
Step
Action
Value(s)
Yes
No
8
If the circuits did not test green and red, check the
following:
• Faulty connector terminal contacts.
• Open circuits, including connections.
• Circuits shorted to ground or voltage.
• Faulty engine control module connector(s) or engine
control module.
Are repairs necessary?
-
Go to Step 13
-
9
1. Check the resistance between the IAC terminal B and
terminal C.
2. Check the resistance between the IAC terminal A and
terminal D.
Is the resistance infinite?
-
Go to Step 11
Go to Step 12
10
Replace the IAC. Refer to On-Vehicle Service, Idle Air
Control Valve.
Is the action complete?
-
Go to Step 7
-
11
Check the IAC valve and circuit.
Are the IAC valve and circuit OK?
-
Refer to
Diagnostic
Aids
Go to Step 12
12
Replace the IAC. Refer to On-Vehicle Service, Idle Air
Control Valve.
Is the action complete?
-
Go to Step 9
-
13
Repair or replace the faulty component(s).
Is the action complete?
-
Go to Step 6
-
DRIVEABILITY AND EMISSIONS 6E1-207
HOT AT ALL TIMES
ECM
Fuse
15A
U/H
FUSE
BLOCK
HOT IN START AND RUN
Meter
Fuse
15A
I/P
FUSE
BLOCK
Malfuntion
Indicator
Lamp
0.85
YEL
1.25
RED/
WHT
1.25
RED/
WHT
0.5
BR/Y
Instrument
Panel(I/P)
Cluster
Engine
Control
Module
(ECM)
A4
A5
B4
Batt+
Malfunction
Indicator
Lamp
Control
TACHO
DIAGNOSTIC TROUBLE CODE (DTC) 56 (Flash DTC = 56)
CHECK ENGINE LAMP LOW ERROR
Circuit Description
The “Check Engine” lamp (MIL) should always be
illuminated and steady with the ignition ON and the
engine stopped. Battery feed Voltage is supplied to the
MIL bulb through the meter fuse. The engine control
module (ECM) turns the MIL ON by grounding the MIL
driver circuit.
Conditions for setting the DTC
• This code detects a low impedance short to ground
on an open contact on the MIL output.
• Driver feedback information shows a low state at its
operation even when commanded high.
Action Taken when the DTC sets
• The MIL will not turn ON.
Conditions for Clearing the 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.
6E1-208 DRIVEABILITY AND EMISSIONS
Diagnostic Aids
An intermittent MIL may be caused by a poor
connection, rubbed-through wire insulation, or a wire
broken inside the insulation. Check for the following
items:
• Inspect the ECM harness and connections for
improper mating, broken locks, improperly formed
or damaged terminals, poor terminal-to-wire
connection, and damaged harness.
• If the engine runs OK, check for a faulty light bulb,
an open in the MIL driver circuit, or an open in the
instrument cluster ignition feed.
• If the engine cranks but will not run, check for an
open ECM ignition or battery feed, or a poor ECM to
engine ground.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. A “No MIL” condition accompanied by a no-start
condition suggests a faulty ECM ignition feed or
battery feed circuit.
9. Using a test light connected to B+, probe each of
the ECM ground terminals to ensure that a good
ground is present. Refer to ECM Terminal End
View for terminal locations of the ECM ground
circuits.
DTC (Flash DTC = 56)
Check Engine Lamp Low Error
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
Attempt to start the engine.
Does the engine start?
-
Go to Step 3
Go to Step 6
3
Check the meter fuse for the instrument cluster turn, back
and gauge.
Is the fuse OK?
-
Go to Step 4
Go to Step 16
5
1. Ignition OFF.
2. Disconnect the ECM.
3. Jumper the MIL driver circuit at the ECM connector to
ground.
4. Ignition ON.
Is the MIL ON?
-
Go to Step 10
Go to Step 11
6
Check the ECM ignition feed and battery feed fuses
(15A Ignition fuse and 15A ECM fuse).
Are both fuses OK?
-
Go to Step 8
Go to Step 15
8
Probe the battery feed circuit at the ECM harness
connector with a test light to ground.
Is the test light ON?
-
Go to Step 9
Go to Step 14
9
Check for a faulty ECM ground connection.
Was a problem found?
-
Verify repair
Go to Step 10
10
Check for damaged terminals at the ECM.
Was a problem found?
-
Verify repair
Go to Step 17
11
Check for an open MIL driver circuit between the ECM and
the MIL.
Was a problem found?
-
Verify repair
Go to Step 18
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