Isuzu engine C22NE / 22LE / 20LE. Manual - part 75

DRIVEABILITY AND EMISSIONS  6E1-129

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

THROTTLE POSITION (TP) SENSOR CIRCUIT RANGE/PERFORMANCE

PROBLEM

Circuit Description

The throttle position (TP) sensor circuit provides a

voltage signal that changes relative to throttle blade

angle. The signal voltage will vary from about 0.25

volts at closed throttle to about 4.75 volts at wide open

throttle (WOT).

The Throttle Position (TP) signal is used by the engine

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

ECM-controlled outputs. The ECM monitors throttle

position and compares actual throttle positions from

the TP sensor to a predicted TP value calculated from

engine speed.

Diagnostic Aids

Check for the following conditions:
• Skewed MAP signal or faulty MAP sensor-An

incorrect MAP signal may cause the ECM to

incorrectly calculate the predicted TP sensor value

during high engine load situations. Check for an

unusually low MAP reading.

• Poor connection at ECM-Inspect harness

connectors for backed-out terminals, improper

mating, broken lock, improperly formed or damaged

terminals, and poor terminal-to-wire connection.

• Damaged Harness-Inspect the wiring harness for

damage: An open Circuit, shorts to Ground, or

shorts to Battery Positive. If the harness appears to

be OK, observe the TP display on the Scan Tool

while moving connectors and wiring harnesses

related to the sensor. A change in the display will

indicate the location of the fault.

6E1-130  DRIVEABILITY AND EMISSIONS

TP Sensor Circuit Range/Performance Problem

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.  Monitor the TP value on the Scan Tool While moving

the throttle between 0% and 100%.

Does the TP value on the Scan Tool move smoothly from

0% (0.25 volts) to 100% (4.75 volts)?

-

Go to Step 3

Go to Step 10

3

1. Ignition OFF.

2.  Disconnect the Throttle Position (TP) Sensor electrical

connector, located on the RH side of the Throttle body.

3.  Start the engine, and monitor the TP value with the

Scan Tool.

Does the TP value on the Scan Tool hold steadily within

the given range?

0-0.25 volts

0%

Go to Step 5

Go to Step 4

4

Check the TP sensor signal circuit, between the TP

sensor and the Engine Control Module (ECM), for a short

to voltage.

Was the problem found?

-

Verify Repair

Go to Step 11

5

Check the TP sensor signal circuit, between the TP

sensor and the ECM, the following conditions:

• A short to ground
• An open circuit

Was the problem found?

-

Verify Repair

Go to Step 6

6

Check the 5 Volt signal circuit between the TP sensor and

the ECM, for the following conditions:

• An Open Circuit
• A short to ground
• A short to voltage

Was the problem found?

-

Verify Repair

Go to Step 7

7

1. Ignition OFF.

2.  Place a fused jumper between the TP sensor circuit

and the 5 volt signal circuit both at the wiring harness

TP sensor connector.

3.  Ignition ON, engine OFF.

4.  Observe the TP value displayed on the Scan Tool.

Does the Scan Tool read the following value?

about 5 volts

100%

Go to Step 8

Go to Step 11

8

Check the TP sensor ground circuit, between the TP

sensor and the ECM, for the following conditions:

• An Open Circuit
• A short to ground
• A short to voltage

Was the problem found?

-

Verify Repair

Go to Step 9

DRIVEABILITY AND EMISSIONS  6E1-131

TP Sensor Circuit Range/Performance Problem (Cont'd)

Step

Action

Value(s)

Yes

No

9

1. Ignition OFF.

2.  Place a Digital Multimeter (DVM), set to measure

voltage between the ground circuit and the 5 volt signal

circuit, both at the wiring harness' TP sensor

connector.

3.  Ignition ON, engine OFF.

Does the DVM indicate the following value?

about 5 volts

Go to Step 10

Go to Step 11

10

Replace the TP sensor.

Verify repair.

-

-

-

11

Replace the EPROM or ECM. 

Note) Refer to 6E1-243.

-

-

-

6E1-132  DRIVEABILITY AND EMISSIONS