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Isuzu engine C22NE / 22LE / 20LE. Manual - part 94

DRIVEABILITY AND EMISSIONS 6E1-205

DTC (Flash DTC = 35)

Idle Air Control (IAC) Error

Step

Action

Value(s)

Yes

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

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

Check the IAC passages.

Are the IAC passages blocked?

Go to Step 4

Go to Step 5

Clear any obstruction from the IAC passages.

Is the action complete?

Verify repair

Replace the IAC. Refer to On-Vehicle Service, Idle Air

Control Valve.

Is the action complete?

Verify repair

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

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

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

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

Replace the IAC. Refer to On-Vehicle Service, Idle Air

Control Valve.

Is the action complete?

Go to Step 7

Check the IAC valve and circuit.

Are the IAC valve and circuit OK?

Refer to

Diagnostic

Aids

Go to Step 12

Replace the IAC. Refer to On-Vehicle Service, Idle Air

Control Valve.

Is the action complete?

Go to Step 9

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)

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

Was the “On-Board Diagnostic (OBD) System

Check” performed?

Go to Step 2

Go to OBD

System

Check

Attempt to start the engine.

Does the engine start?

Go to Step 3

Go to Step 6

Check the meter fuse for the instrument cluster turn, back

and gauge.

Is the fuse OK?

Go to Step 4

Go to Step 16

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

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

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

Check for a faulty ECM ground connection.

Was a problem found?

Verify repair

Go to Step 10

Check for damaged terminals at the ECM.

Was a problem found?

Verify repair

Go to Step 17

Check for an open MIL driver circuit between the ECM and

the MIL.

Was a problem found?

Verify repair

Go to Step 18

Content .. 92 93 94 95 ..