Content .. 86 87 88 89 ..

Isuzu engine C22NE / 22LE / 20LE. Manual - part 88

DRIVEABILITY AND EMISSIONS 6E1-181

HOT AT ALL TIMES

Ignition

Coil

Fuse

15A

I/P

FUSE

BLOCK

Engine

Control

Module

(ECM)

HOT AT ALL TIMES

ECM

Fuse

15A

U/H

FUSE

BLOCK

1.25

RED/

WHT

1.25

BLK

1.25

BLK

W/G

1.25

RED/

WHT

Batt+

Ignition

Coil

A13

0.5

G/W

Ignition Feeds

1,4

2,3

Relay

Fuel

Pump

ECM

Fuse

15A

F/Pump

Fuse

20A

DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 49)

SYSTEM VOLTAGE HIGH

Circuit Description

The engine control module (ECM) monitors the

system voltage on the ignition feed terminal to the

ECM. A system voltage Diagnostic Trouble Code will

set whenever the voltage is above a calibrated value.

This malfunction detects an over-voltage condition in

the battery voltage circuit.

Conditions for Setting the DTC

• Engine is running.
• Battery Voltage is greater than 17.2V.

Action Taken When the DTC Sets

• The ECM will illuminate the malfunction indicator

lamp (MIL) for the first time the malfunction 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 a faulty charging system components.

6E1-182 DRIVEABILITY AND EMISSIONS

DTC (Flash DTC = 49)

System Voltage High

Step

Action

Value(s)

Yes

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

performed?

Go to Step 2

Go to OBD

System Check

1. Ignition OFF, engine OFF.

2. Using a Digital Voltmeter (DVM), measure the battery

voltage at the battery.

Is the battery voltage greater than the specified value?

16V

Go to Step 3

Go to Step 4.

1. Charge the battery and clean the battery terminals.

2. Clean the battery ground cable connection if corrosion

is indicated.

Is the battery voltage greater than the specified value?

16V

Replace battery

Go to Step 4

1. Turn OFF all the accessories.

2. Install the Scan Tool.

3. Select the ignition voltage parameter on the data list.

4. Start the engine and raise the engine speed to 2000

RPM.

Is it the voltage above the specified value?

16V

Go to Step 5

Go to Step 6

Replace or repair the generator (see Charging System).

Is a malfunction present?

Verify Repair

Replace the EPROM or ECM.

Is the action complete?

Note) Refer to 6E1-243.

Verify Repair

DRIVEABILITY AND EMISSIONS 6E1-183

0.5
G

0.5
GR

0.5
R

0.5

0.5
YEL/
GRN

Engine

Control

Module

(ECM)

F10

IAT
Sensor
Input

Sensor
Ground

Intake Air
Temperature
(IAT)
Sensor

MAP

Sensor

DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 69)

INTAKE AIR TEMPERATURE (IAT) SENSOR TOO HIGH

Circuit Description

The intake air temperature (IAT) sensor is a thermistor

which measures the temperature of the air entering

the engine. The engine control module (ECM) applies

5 volts through a pull-up resistor to the IAT sensor.

When the intake air is cold, the sensor resistance is

high and the ECM will monitor a high signal voltage on

the IAT signal circuit. If the intake air is warm, the

sensor resistance is lower, causing the ECM to

monitor a lower voltage. Diagnostic Trouble Code 69

will set when the ECM detects an excessively high

signal voltage on the intake air temperature sensor

signal circuit.

Conditions for Setting the DTC

• The engine is running.
• IAT sensor temperature is greater than 140 degC.
The above conditions are met.

Action Taken When the DTC Sets

• The ECM will illuminate the malfunction indicator

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

• The ECM will use a default IAT value based on

ECM inputs and engine run time.

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 ECM - Inspect harness

connectors for backed-out terminals, improper

6E1-184 DRIVEABILITY AND EMISSIONS

mating, broken locks, improperly formed or

damaged terminals, and poor terminal-to-wire

connection.

• Damaged harness - Inspect the wiring harness for

damage, shorts to Ground, shorts to Battery

Positive, and Open Circuits. If the harness appears

to be OK, observe the IAT display on the Scan Tool

while moving connectors and wiring harnesses

related to the IAT sensor. A change in the IAT

display will indicate the location of the fault.

If Diagnostic Trouble Code 69 cannot be duplicated,

the information included in the Failure Records data

can be useful in determining vehicle mileage since the

Diagnostic Trouble Code was last set.

Test Description

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

Diagnostic Chart.

2. Verifies that the fault is present.

3. If Diagnostic Trouble Code 69 can be repeated

only by duplicating the Failure Records conditions,

refer to the "Temperature vs. Resistance Values"

table. The table may be used to test the IAT sensor

at various temperatures to evaluate the possibility

of a "shifted" sensor that may be open above or

below a certain temperature. If this is the case,

replace the IAT sensor. If the IAT sensor appears

to be OK, the fault is intermittent; refer to

Diagnostic Aids.

Intake Air Temperature Sensor

°C

°F

OHMS

Temperature vs. Resistance Values

(approximate)

100

212

177

176

332

140

667

113

1188

1802

2796

4450

7280

−5

12300

−15

21450

−30

−22

52700

−40

100700

DTC (Flash DTC = 69)

Intake Air Temperature (IAT) Sensor Too High

Step

Action

Value(s)

Yes

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

performed?

Go to Step 2

Go to OBD

System

Check

Ignition ON, engine OFF Observe the "Intake Air Temp"

values displayed on the Scan Tool.

Is the "Intake Air Temp" values below the specified value?

−36°C

(

−32.8°F)

Go to Step 4

Go to Step 3

1. Ignition ON, engine OFF.

2. Using a Scan Tool, monitor info for Diagnostic Trouble

Code 69.

Does the Scan Tool indicate Diagnostic Trouble Code 69

failed?

Refer to Test

Description

Refer to

Diagnostic

Aids

1. Ignition OFF.

2. Disconnect the IAT sensor electrical connector.

3. Jumper the IAT signal circuit and the sensor ground

circuit together at the IAT sensor harness connector.

4. Ignition ON.

5. Observe the "Intake Air Temp" values displayed on the

Scan Tool.

Is the "Intake Air Tempe" values at the specified value?

140°C

(284°F)

Go to Step 6

Go to Step 5

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