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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

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

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

Replace the IAT sensor.

Is the action complete?

Verify repair

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

E16

Fuel

Injector

Control

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

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

performed?

Go to Step 2

Go to OBD

System

Check

Will the engine start?

Go to Step 3

Cranks But

Will Not Run

Chart

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

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

Content .. 88 89 90 91 ..