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Isuzu engine C22NE / 22LE / 20LE. Manual - part 85

DRIVEABILITY AND EMISSIONS 6E1-169

Engine

Control

Module

(ECM)

CKP

Sensor

Input

Sensor

Ground

0.5

Crankshaft

Position

(CKP)

Sensor

DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 19)

CRANKSHAFT POSITION (CKP) SENSOR SIGNAL INCORRECT

Circuit Description

The 58X reference signal is produced by the

crankshaft position (CKP) sensor. During one

crankshaft revolution, 58 crankshaft pulses will be

produced. The engine control module (ECM) uses the

58X reference signal to calculate engine RPM and

crankshaft position. The ECM constantly monitors the

number of pulses on the 58X reference circuit. If the

ECM receives an incorrect number of pulses on the

58X reference circuit, Diagnostic Trouble Code 19 will

set.

Conditions for Setting the DTC

• Engine is running.
• Number of revolutions with pulses not equal to 58 is

greater than 20.

Action Taken When the DTC Sets

• The ECM will illuminate the malfunction indicator

lamp (MIL) after 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

An intermittent may be caused by a poor connection,

rubbed-through wire insulation or a wire broken inside

the insulation. Check for:
• Poor connection - Inspect the ECM harness and

connectors for improper mating, broken locks,

improperly formed or damaged terminals, and poor

terminal-to-wire connection.

6E1-170 DRIVEABILITY AND EMISSIONS

• 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, disconnect the ECM, turn the ignition on

and observe a voltmeter connected to the 58X

reference circuit at the ECM harness connector

while moving connectors and wiring harnesses

related to the ECM. A change in voltage will indicate

the location of the fault.

• This code detects an incorrect 58X signal caused

by intermittent failures.

DTC (Flash DTC = 19)

Crankshaft Position (CKP) Sensor Signal Incorrect

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

Refer to

Engine

Cranks But

Will Not Run

chart

1. Clear Diagnostic Trouble Code 19.

2. Start the engine and idle for 1 minute.

3. Observe Diagnostic Trouble Codes.

Is Diagnostic Trouble Code 18 set?

Go to Step 4

Refer to

Diagnostic

Aids

1. Disconnect the ECM and CKP sensor.

2. Check for an open or a short to ground in the 58X

reference circuit between the CKP sensor connector

and the ECM harness connector.

3. If a problem is found, repair as necessary.

Was a problem found?

Verify repair

Go to Step 5

1. Reconnect the ECM and CKP sensor.

2. Connect a Digital Voltmeter (DVM) to measure voltage

on the 58X reference circuit at the ECM connector.

3. Observe the voltage while cranking the engine.

Is the voltage near the specified value?

2.5V

Go to Step 8

Go to Step 6

Check the connections at the CKP sensor and replace the

terminals if necessary.

Did any terminals require replacement?

Verify repair

Go to Step 7

Replace the CKP sensor.

Is the action complete?

Verify repair

Check connections at the ECM and replace the terminals

if necessary.

Did any terminals require replacement?

Verify repair

Go to Step 9

Replace the EPROM or ECM.

Is the action complete?

Note) Refer to 6E1-243.

Verify repair

DRIVEABILITY AND EMISSIONS 6E1-171

DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 24)

VEHICLE SPEED SENSOR (VSS) FAULT

Circuit Description

The vehicle speed sensor has a magnet rotated by the

transmission output shaft. Attached to the sensor is a

hall effect circuit that interacts with the magnetic field

created by the rotating magnet. A 12-volt operating

supply for the speed sensor hall circuit is supplied

from the meter fuse. The VSS pulses to ground the 5-

volt signal sent from the engine control module (ECM)

on the reference circuit. The ECM interprets vehicle

speed by the number of pulses to ground per second

on the reference circuit. Then a DTC 24 will set.

Conditions for Setting the DTC

• Vehicle speed is less than 3 km/h.
• Engine is running.
• MAP is less than 24kPa.
• Throttle closed and in Drive.
• Engine Speed is between 2000 RPM and 5000

RPM.

• Following malfunctions are not set: DTC 21, 22, 33,

34 are not set.

When the above conditions are met, one of the

following tests will run:

Action Taken When the DTC Sets

• The ECM will illuminate the malfunction indicator

lamp (MIL) 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.

6E1-172 DRIVEABILITY AND EMISSIONS

Diagnostic Aids

• Poor connection at the ECM: Inspect harness

connectors for backed out terminals, improper

mating, broken locks, improperly formed or

damaged terminals, and poor terminal to wire

connection.

• Damaged harness: Inspect the wiring harness to

the Speedometer, Tachometer and check Engine

Lamp for an intermittent open or intermittent short

circuit.

DTC (Flash DTC = 24)

Vehicle Speed Sensor (VSS) Fault

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.

2. Disconnect the VSS connector.

3. Using a test light to battery

+, probe the connector

ground wire.

Did the light illuminate?

Go to Step 4

Go to Step 3

Repair the open in the sensor ground circuit.

Verify repair

1. Ignition ON.

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

connector between ground and voltage supply.

Was the measurement near the specified value?

Battery

voltage

Go to Step 6

Go to Step 5

Repair the open or short to ground in the sensor circuit.

Verify repair

1. Ignition OFF.

2. Check the white wire between the VSS sensor

connector and the ECM for the following conditions:

• An open circuit
• A short to ground
Was the faulty condition located?

Verify repair

Go to Step 9

Using a DVM, measure the resistance between the VSS

sensor body and transmission case (ground).

Is the resistance above the specified value?

10K

OHMS

Verify repair

Go to Step 9

1. Remove the VSS from the transmission case.

2. Visually inspect the VSS for damage.

Does the VSS appear to be OK?

Verify repair

Replace the VSS

Verify repair

Replace the EPROM or ECM.

Verify repair.

Note) Refer to 6E1-243.

Verify repair

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