Content .. 84 85 86 87 ..

Isuzu engine C22NE / 22LE / 20LE. Service manual - part 86

DRIVEABILITY AND EMISSIONS 6E1-173

0.5

YEL/

GRN

0.5

GRN

0.5

RED

0.5

RED

0.5

GRN

0.5

RED

Manifold

Absolute

Pressure

(MAP)

Sensor

F10

0.5

GRN

5 Volt

Reference

Signal

MAP Sensor

Input

Sensor

Ground

0.75

A B

Intake

Air Temperature

Sensor

Throttle Position

Sensor

Engine

Control

Module

(ECM)

OUT

0.5

DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 33)

MANIFOLD ABSOLUTE PRESSURE (MAP) TOO HIGH

Circuit Description

The manifold absolute pressure (MAP) sensor

responds to changes in intake manifold pressure. The

MAP sensor signal voltage to the engine control

module (ECM) varies from below 2 volts at idle (low

manifold pressure) to above 4 volts with the ignition

ON, engine not running or at wide-open throttle (high

manifold pressure).

A "speed density" method of determining engine load

is used. This is calculated using inputs from the MAP

sensor, the CKP Sensor, and the Intake Air

Temperature (IAT) sensor. The MAP sensor is the

main sensor used in this calculation, and measuring

engine load is its main function. The ECM monitors

the MAP signals for voltages outside the normal range

of the MAP sensor. This code defects a short to MAP

signal voltage in the MAP sensor circuit. Diagnostic

Trouble Code 33 will be set.

Conditions for Setting the DTC

• No TP sensor Diagnostic Trouble Codes 21 or 22

present.

•  Engine is running.
•  Not in power enrich mode.
• Throttle Position Sensor value is less than 1%.
•  Altitude Compensated Manifold Absolute Pressure

is greater than 95kpa.

Action Taken When the DTC Sets

• The ECM will illuminate the malfunction indicator

lamp (MIL).

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.

6E1-174 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, shorts to Ground, shorts to Battery

positive, and Open circuits. If the harness appears

to be OK, observe the MAP 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.

DTC (Flash DTC = 33)

Manifold Absolute Pressure (MAP) 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

1. If the engine idle is rough, unstable or incorrect, repair

the idle problem before using this chart.

Refer to Symptoms section.

2. With the engine idling, note the MAP value on the Scan

Tool.

Is the MAP reading above the specified value?

About 4V

90 kPa

Go to Step 4

Go to Step 3

1. Ignition ON engine OFF.

2. Using the Scan Tool, monitor info for Diagnostic

Trouble Code 33.

Does the Scan Tool indicate Diagnostic Trouble Code 33

failed?

Go to Step 4

Refer to

Diagnostic

Aids

1. Ignition OFF.

2. Disconnect the MAP sensor electrical connector.

3. Ignition ON.

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

Is the MAP value near the specified value?

10.3 Kpa

Go to Step 5

Go to Step 6

Check the MAP sensor signal circuit, between the MAP

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

to voltage.

Was the problem found?

Verify Repair

Go to Step 12

Check the MAP sensor signal circuit, between the MAP

sensor and the ECM for the following conditions:
• A short to ground
• An open circuit
Was the problem found?

Verify repair

Go to Step 7

Check the 5 volt signal circuit, between the MAP sensor

and the ECM for the following conditions:
• A short to ground
• An open circuit
• A short to voltage
Was the problem found?

Verify Repair

Go to Step 8

DRIVEABILITY AND EMISSIONS 6E1-175

DTC (Flash DTC = 33)

Manifold Absolute Pressure (MAP) Too High (Cont'd)

Step

Action

Value(s)

Yes

1. Ignition OFF.

2. Place a fused jumper between the MAP sensor circuit

and the 5 volt signal circuit, both at the wiring harness'

MAP sensor connector.

3. Ignition ON, Engine OFF.

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

Does the Scan Tool read the following value?

5 Volts

104 kPa

Go to Step 9

Go to Step 12

Check the MAP sensor ground circuit, between the MAP

sensor and the ECM, for the following conditions:
• A short to ground
• An open circuit
• A short to voltagen
Was the problem found?

Verify Repair

Go to Step 10

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' MAP sensor

connector.

3. Ignition ON, Engine OFF.

Does the DVM read the following value?

5 Volts

Go to Step 11

Go to Step 12

Replace the MAP Sensor.

Verify Repair.

Replace the EPROM or ECM.

Verify Repair.

Note) Refer to 6E1-243.

6E1-176 DRIVEABILITY AND EMISSIONS

Content .. 84 85 86 87 ..