Isuzu KB P190. Manual - part 583

6E–162

ENGINE DRIVEABILITY AND EMISSIONS

10

Check for the following conditions. 

• Objects blocking the IAC valve. 

• Objects blocking the throttle valve. 

• Vacuum leaking at throttle body. 
If a problem is found, repair as necessary. 
Was the problem found?

—

Verify repair

Go to Step 11

11

Check for injector for the affected bank. 
Refer to “Injector Coil Test & Injector Balance Test
Procedure” 6E-98 page. 
Was the injector operation correct?

—

Go  to  Step 12

Refer to Injector 

Coil Test & 

Injector 

Balance Test 

Procedure

12

Check for fuel pressure. 
Refer to “Fuel System Diagnosis” 6E-108 page. 
Was the fuel pressure correct? 

—

Go to Step 13

Refer to Fuel 

System 

Diagnosis

13

Replace the O

2

 sensor. 

Was the problem solved?

—

Verify repair

Go to Step 14

14

Is the ECM programmed with the latest software
release? 
If not, download the latest software to the ECM using
the “SPS (Service Programming System)”. 
Was the problem solved?

—

Verify repair

Go to Step 15

15

Replace the ECM. 
Is the action complete? 
IMPORTANT:  The replacement ECM must be
programmed. Refer to section of the Service
Programming System (SPS) in this manual. 
Following ECM programming, the immobilizer system
(if equipped) must be linked to the ECM. Refer to
section 11 “Immobilizer System-ECM replacement” for
the ECM/Immobilizer linking procedure.

—

Verify repair

—

Step

Action

Value(s)

Yes

No

ENGINE DRIVEABILITY AND EMISSIONS

6E–163

DIAGNOSTIC TROUBLE CODE (DTC) P0135 O

2

 SENSOR HEATER CIRCUIT 

(BANK 1 SENSOR 1)

Condition for setting the DTC and action taken when the DTC sets

Circuit Description

Heated oxygen sensors are used to minimize the
amount of time required for “Closed Loop” fuel control
operation and to allow accurate catalyst monitoring. The
oxygen sensor heater greatly decreases the amount of
time required for fuel control sensors Bank 1 HO2S 1 1
to become active. Oxygen sensor heaters are required
by catalyst monitor sensors Bank 1 HO2S 2 to maintain
a sufficiently high temperature which allows accurate
exhaust oxygen content readings further from the

engine.
The engine control module (ECM) will run the heater
test only after a cold start (determined by engine coolant
and intake air temperature at the time of start-up) and
only once during an ignition cycle. When the engine is
started the ECM will monitor the HO2S voltage. When
the HO2S voltage indicates a sufficiently active sensor,
the ECM looks at how much time has elapsed since
start-up. If the ECM determines that too much time was
required for the Bank 1 HO2S 1 to become active, a
Diagnostic Trouble Code P0135 will set.

Code

Type

DTC Name

DTC Setting Condition

Fail-Safe (Back Up)

P0135

A

O

2

 SensorHeater Circuit (Bank 1 Sen-

sor 1)

1. No DTC relating to MAP sensor and ECT 

sensor. 

2. Engine coolant temperature is more than 

60 deg. C. 

3. Engine run time is longer than 20 seconds. 
4. MAP sensor output is more than 70kPa. 
5. O

2

 sensor bank 1 heater current more than 

10mA.

No fail-safe function.

6E–164

ENGINE 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.

Diagnostic Trouble Code (DTC) P0135 

O

2

 Sensor Heater Circuit (Bank 1 Sensor 1)

Step

Action

Value(s)

Yes

No

1

Was the “On-Board Diagnostic (OBD) System Check”
performed?

—

Go  to Step 2

Go to On Board 

Diagnostic 

(OBD) System 

Check

2

1. Connect the Tech 2. 

2. Review and record the failure information. 

3. Select “F0: Read DTC Infor By Priority” in “F0:

Diagnostic Trouble Code”. 

Is the DTC P0135 stored as “Present Failure”?

—

Go to Step 3

Refer to 

Diagnostic Aids 

and Go to Step 

3

3

1. Using the Tech2, ignition “On” and engine “Off”. 

2. Select “Clear DTC Information” with the Tech2 and

clear the DTC information. 

3. Operate the vehicle and monitor the “F5: Failed

This Ignition” in “F2: DTC Information”.

Was the DTC P0135 stored in this ignition cycle?

—

Go to Step 4

Refer to 

Diagnostic Aids 

and Go to Step 

4

4

Check for poor/faulty connection at the O

2

 sensor or

ECM connector. If a poor/faulty connection is found,
repair as necessary. 
Was the problem found?

—

Verify repair

Go to Step 5

5

Visually check the O

2

 sensor. 

Was the problem found? 

—

Go to Step 11

Go to Step 6

6

Using the DVM and check the O

2

 sensor.

1.  Ignition “Off”,  engine “Off”. 

2. Disconnect O

2

 sensor connector 

3. Measure the resistance of heater. 

Was the tester indicated specified value? 

Approximately 
12.5

Ω at 20°C

Go to Step 7

Go to Step 11

3 4

31

C56(J2)

E77

3

4

1

2

3

4

O

2

 Sensor

ENGINE DRIVEABILITY AND EMISSIONS

6E–165

7

Using the DVM and check the heater power supply
circuit for the affected cylinder.

1. Ignition “On”, engine “Off”. 

2. Disconnect the O

2

 sensor connector. 

3. Check the circuit for open circuit. 

Was the DVM indicated specified value?

10 - 14.5V

Go to Step 9

Go to Step 8

8

Repair the open or short to ground circuit between the
“O

2

 Sensor” fuse (10A) and O

2

 sensor. 

Is the action complete?

—

Verify repair

—

9

Using the DVM and check the heater ground circuit.
Breaker box is available: 

1. Ignition “Off”, engine “Off”. 

2. Install the breaker box as type A. (ECM

disconnected) Refer to 6E-88 page.

3. Disconnect the O

2

 sensor connector. 

4. Check the circuit for open or short to ground

circuit. 

Was the problem found?

Breaker box is not available: 

1. Ignition “Off”, engine “Off”. 

2. Disconnect the O

2

 sensor connector and ECM

connector. 

3. Check the circuit for open or short to ground

circuit. 

Was the problem found?

—

Repair faulty 

harness and 

verify repair

Go to Step 10

Step

Action

Value(s)

Yes

No

4

V

E77

J2-31

Breaker Box

E-77

3

Ω

Ω

3

31

E56(J2)

E77