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Isuzu engine C22NE / 22LE / 20LE. Manual - part 93

DRIVEABILITY AND EMISSIONS 6E1-201

HOT IN START AND RUN

IG.

Coil

Fuse

15A

I/P

FUSE

BLOCK

W/G

Ignition

Coil

Ignition

Coil

1.25

Engine

Control

Module

(ECM)

Electronic Spark

Timing Control

1.25

BLK

1.25

BLK

1,4

2,3

DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 64)

IGNITION COIL DRIVER "A" SHORT TO GROUND

Circuit Description

The ignition control circuit in ECM provides a zero volt

or a 5 volt signal to the ignition coil driver. The normal

circuit voltage is zero volts. When the coil driver

receives the 5 volt signal from the ignition control

circuit, it provides a ground path for the B+ voltage

supplied to the ignition primary coil. When the ECM

turns off the 5 volts to the module, the module will

remove the ground path of the ignition primary coils;

causing the magnetic field produces a voltage in the

secondary coils which fires the spark plug.

The circuit between the coil driver and the ignition

control circuit is monitored for a short to ground on the

Electronic Spark Timing A/coil drive A line. When the

ECM detects a problem in the ignition control circuit, it

will set DTC 64.

Conditions for Setting the DTC

• Fault feedback line generates an interrupt on end of

dwell.

• No Electronic Spark Timing activation requested by

serial data.

Action Taken When the DTC Sets

• The ECM will illuminate the malfunction indicator

lamp (MIL) the first time the fault is detected.

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

Check for the following conditions:
• Poor connection at the ECM - Inspect the harness

connectors for backed-out terminals, improper

mating, broken locks, improperly formed or

6E1-202 DRIVEABILITY AND EMISSIONS

damaged terminals, and poor terminal-to-wire

connections.

• Damaged harness - Inspect the wiring harness for

damage; Open circuits, shorts to ground, or shorts

to Voltage. If the harness appears to be OK,

observe the Scan Tool display related to DTC 64

while moving the connector and wiring related to the

ignition system. A change in the display will indicate

the location of the fault.

• This code detects a short to ground on the

Electronic Spark Timing A/Coil Driver A (#1, #4 cyl.)

line.

DTC (Flash DTC = 64)

Ignition Coil Driver "A" Short To Ground

Step

Action

Value(s)

Yes

Was the "On-Board Diagnostic (OBD) System Check"

performed?

Go to Step 2

Go to OBD

System

Check

Check for a faulty connection or damaged terminals at the

ignition control module.

Was a problem found?

Verify repair

Go to Step 3

Check for a faulty connection or damaged terminals at the

ECM connector.

Was a problem found?

Verify repair

Go to Step 4

Check for a open circuit between the ignition coil and

ECM.

If a problem is found, repair the wire harness.

Is there still a problem?

Verify repair

Go to Step 5

Check for a short to ground between the ignition coil and

battery +.

If a problem is found, repair the wire harness.

Is there still a problem?

Verify repair

Go to Step 6

1. Ignition OFF.

2. Disconnect the ignition coil.

3. Check the ignition control circuit for a short to voltage.

Was a problem found?

Verify repair

Go to Step 7

Replace the ignition control module.

Verify repair.

Is there still a problem?

Go to Step 8

Replace the EPROM or ECM.

Is the repair complete?

Note) Refer to 6E1-243.

Verify repair

DRIVEABILITY AND EMISSIONS 6E1-203

Engine

Control

Module

(ECM)

B16

0.5

L/W

0.5

L/R

Idle Air

Control

(IAC)

Valve

0.5

L/B

B15

B13

B14

IAC

High

IAC

Low

IAC

High

IAC

Low

DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 35)

IDLE AIR CONTROL (IAC) ERROR

Circuit Description

The engine control module (ECM) controls engine idle

speed with the idle air control (IAC) valve. To increase

idle speed, the ECM retracts the IAC valve pintle away

from its seat, allowing more air to bypass the throttle

bore. To decrease idle speed, it extends the IAC valve

pintle towards its seat, reducing bypass air flow. A

Scan Tool will read the ECM commands to the IAC

valve in counts. Higher counts indicate more air

bypass (higher idle). Lower counts indicate less air is

allowed to bypass (lower idle).

This malfunction detects an error in the IAC control

logic, then DTC 35 will set.

Conditions for setting the DTC

• Engine rpm error is greater than 175 rpm.
• No DTC 21, 22 and 24 present.
And,
• Engine desired rpm is not fixed by tester.
• IAC movement is not inhibited by low or high battery

voltage.

And,
• IAC normal closed loop is enabled.
• Coolant of lesets are decayed to 0.

6E1-204 DRIVEABILITY AND EMISSIONS

Action Taken when the DTC sets

• The ECM will illuminate the malfunction indicator

lamp (MIL).

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

A slow, unstable, or fast idle may be caused by a non-

IAC system problem that cannot be overcome by the

IAC valve. Out of control range IAC Scan Tool counts

will be above 60 if idle is too low, and zero counts if

idle is too high. The following checks should be made

to repair a non-IAC system problem:
• Vacuum leak (high idle) - If idle is too high, stop the

engine. Fully extend (low) IAC with the IAC motor

analyzer 5-8840-2312-0. Start the engine. If idle

speed is above 825 RPM, locate and correct the

vacuum leak, including the PCV system. Check for

binding of the throttle blade or linkage.

Following are applicable to the vehicle with

closed Loop System.

• Throttle body - Remove the IAC valve and inspect

the bore for foreign material.

• IAC valve electrical connections - IAC valve

connections should be carefully checked for proper

contact.

• PCV hose - An incorrect or faulty hose may result in

an incorrect idle speed. Refer to Diagnosis, Rough

Idle, Stalling. If intermittent poor driveability or idle

symptoms are resolved by disconnecting the IAC,

carefully recheck the connections and valve

terminal resistance, or replace the IAC.

• Lean heated oxygen sensor signal (high air/fuel

ratio) - The idle speed may be too high or too low.

Engine speed may vary up and down, and

disconnecting the IAC valve does not help.

Diagnostic trouble code 44 may be set. Scan Tool

oxygen (O2) voltage will be less than 27 mV (2.74

V). Check for low regulated fuel pressure, waterin

fuel, or a restricted injector.

• Rich heated oxygen sensor signal (low air/fuel ratio)

- The idle speed will be too low. Scan Tool IAC

counts will usually be above 80. The system is

obviously rich and may exhibit black smoke in the

exhaust.

• Scan Tool O2 voltage will be fixed at about 750 mV

(0.75 V). Check for high fuel pressure, or a leaking

or sticking injector. A silicon-contaminated heated

oxygen sensor will show an O2 voltage slow to

respond on the Scan Tool.

Test Description

Number(s) below refer to the step number(s) on the

Diagnostic Chart.

1. The IAC motor analyzer 5-8840-2312-0 is used to

extend and retract the IAC valve. Valve movement

is verified by an engine speed change. If no

change in engine speed occurs, the valve can be

resettled when removed from the throttle body.

2. This step checks the quality of the IAC movement

in step 1. Between 700 revolutions per minute

(RPM) and about 1500 RPM, the engine speed

should change smoothly with each flash of the

tester light in both extend and retract. If the IAC

valve is retracted beyond the control range (about

1500 RPM), it may take many flashes to extend the

IAC valve before engine speed will begin to drop.

This is normal on certain engines. Fully extending

the IAC may cause engine stall. This may be

normal.

6. Steps 1 and 2 verified the proper IAC valve

operation. This step checks the IAC circuits. Each

lamp on the noid light should flash red and green

while the IAC valve is cycled. While the sequence

of color is not important, if either light is OFF or

does not flash red and green, check the circuits for

faults, beginning with poor terminal contacts.

Content .. 91 92 93 94 ..