Isuzu engine C22NE / 22LE / 20LE. Service manual — part 76

DRIVEABILITY AND EMISSIONS 6E1-133

0.5

R

0.5

G

0.5

GR

0.5

RED

0.75

GRN

0.75

L

0.5

GRN

Engine

Control

Module

(ECM)

F14

B1

A3

5 Volt

Reference

Signal

Throttle

Position

(TP)

Sensor

Input

Sensor

Ground

Sensor

Ground

B7

B2

Throttle

Position

(TP)

Sensor

B C

A

Manifold

Absolute

Pressure

Sensor

Engine

Coolant

Temperature

Sensor

B8

LO

HI

OUT

0.5

L/R

DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 22)

THROTTLE POSITION (TP) SENSOR CIRCUIT LOW INPUT

Circuit Description

The throttle position (Throttle Position) sensor circuit

provides a voltage signal that changes relative to

throttle blade angle. The signal voltage will vary from

below 1 volt at closed throttle to about 4 volts at wide

open throttle (WOT).

The Throttle Position signal is used by the engine

control module (ECM) for fuel control and most of the

ECM-controlled outputs. If the ECM detects a low

inpedance short to ground in the Throttle Position

sensor or circuit, then a code 22 will set.

Conditions for Setting the DTC

• Throttle Position sensor signal voltage is less than

0.19 volt.

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 throttle position based

on RPM.

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.

6E1-134 DRIVEABILITY AND EMISSIONS

Diagnostic Aids

Check for the following conditions:
• Poor connection at 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 for

damage. If the harness appears to be OK, observe

the throttle position display on the Scan Tool while

moving connectors and wiring harnesses related to

the throttle Position sensor. A change in the display

will indicate the location of the fault.

DTC (Flash DTC = 22)

Throttle Position (TP) Sensor Circuit Low Input

Step

Action

Value(s)

Yes

No

1

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

performed?

-

Go to Step 2

Go to OBD

System

Check

2

1. Ignition ON, engine OFF.

2. With the throttle closed, observe the "Throttle Position

Sensor" display on the Scan Tool. is the "Throttle

Position Sensor" below the specified value?

0.19V

Go to Step 4

Go to Step 3

3

1. Ignition ON engine OFF.

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

Code 22.

Does the Scan Tool indicate Diagnostic Trouble Code 22

failed?

-

Go to Step 4

Refer to

Diagnostic

Aids

4

1. Ignition OFF.

2. Disconnect the Throttle Position sensor electrical

connector.

3. Jumper the 5 volt reference circuit and the Throttle

Position signal together at the Throttle Position sensor

harness connector.

4. Ignition ON.

Observe the "Throttle Position Sensor" value displayed

on the Scan Tool.

Is the "Throttle Position Sensor" at the specified value?

5V

Go to Step 10

Go to Step 5

5

1. Disconnect jumper.

2. Connect a test light between B+ and the Throttle

Position sensor signal circuit at the Throttle Position

sensor harness connector.

Observe the "Throttle Position Sensor" value displayed

on the Scan Tool.

Is the "Throttle Position Sensor" at the specified value?

5V

Go to Step 6

Go to Step 8

DRIVEABILITY AND EMISSIONS 6E1-135

DTC (Flash DTC = 22)

Throttle Position (TP) Sensor Circuit Low Input (Cont'd)

Step

Action

Value(s)

Yes

No

6

1. Ignition OFF.

2. Disconnect the ECM and check the 5 volt reference

circuit for an open or short to ground.

3. If the 5 volt reference circuit is open or shorted to

ground, repair it as necessary.

Was the 5 volt reference circuit open or shorted to

ground?

-

Verify repair

Go to Step 7

7

Check the 5 volt reference circuit for a poor connection at

the ECM and replace the terminal if necessary.

Did the terminal require replacement?

-

Verify repair

Go to Step 12

8

1. Ignition OFF.

2. Disconnect the ECM, and check the Throttle Position

signal circuit for an open, short to ground, or short to

the sensor ground circuit.

3. If the Throttle Position sensor signal circuit is open or

shorted to ground, repair it as necessary.

Was the Throttle Position signal circuit open or shorted to

ground?

-

Verify repair

Go to Step 9

9

Check the Throttle Position sensor signal circuit for a poor

connection at the ECM and replace the terminal if

necessary.

Did the terminal require replacement?

-

Verify repair

Go to Step 12

10

Check the Throttle Position sensor signal circuit for a poor

connection at the Throttle Position sensor and replace the

terminal if necessary.

Did the terminal require replacement?

-

Verify repair

Go to Step 11

11

Replace the Throttle Position sensor.

Is the action complete?

-

Verify repair

-

12

Replace the EPROM or ECM.

Is the action complete?

Note) Refer to 6E1-243.

-

Verify repair

-

6E1-136 DRIVEABILITY AND EMISSIONS