Isuzu KB P190. Manual - part 828

Engine Management – V6 – Diagnostics 

Page 6C1-2–34 

 

Checks Actions 

Additional Checks 

• 

Check the exhaust system for possible restrictions. Refer to 6F Exhaust System – 
V6. 

• 

Electromagnetic interference (EMI) on the crankshaft position (CKP) sensor can 
cause an engine misfire condition.  

 

Using Tech 2, monitor the engine speed parameter. A sudden increase in the 
engine speed parameters without moving the throttle position indicates that an 
Electromagnetic Interference fault may be present.  

 

Wiring harness routing which may be positioned very close to a high voltage or 
high current device such as the following may induce EMI: 

• 

secondary ignition components, and 

• 

motors and generators. 

• 

Check the torque converter clutch (TCC) operation. A TCC that applies too soon 
can cause engine detonation, which will trigger spark retard activity. Refer to 7C2 
Automatic Transmission – 4L60E – Electrical Diagnosis. 

• 

Test for other TCM related faults that may cause the transmission to operate in 
the default mode. Refer to 7C2 Automatic Transmission – 4L60E – Electrical 
Diagnosis. 

• 

Check for transmission mechanical faults such as slipping clutch. Refer to 7C3 
Automatic Transmission – 4L60E – Hydraulic and Mechanical Diagnosis. 

• 

Check the brake system including the parking brake for sticking or incorrect 
operation.  

When all diagnosis and repairs are completed, check the system for correct operation. 

5.12  Rough, Unstable, Incorrect Idle or 

Stalling 

Description 

Engine idle speed fluctuates causing the engine to run unevenly. If the engine idle speed drops too low, the engine may 
stall. 

Checks Actions 

Preliminary 

• 

Perform the preliminary checks. Refer to 4.3 

Preliminary Checks in this 

Section. 

• 

Check the air filter element and intake air ducts for blockages. 

Sensor / System 

• 

Check the throttle actuator control (TAC) system. Refer to 6C1-3 Engine 
Management – V6 – Service Operations. 

• 

Check the air intake system and crankcase for air leaks. Refer to 6C1-3 Engine 
Management – V6 – Service Operations. 

• 

Check the PCV System for correct operation. Refer to 6A1 Engine Mechanical – 
V6. 

• 

Use Tech 2 to monitor the knock sensor system for excessive spark retard 
activity. Check for items that cause spark retard activity.  

• 

Using Tech 2, check the heated oxygen sensor (HO2s) operating parameters. 
The HO2s sensor should respond quickly to different throttle positions. 

Engine Management – V6 – Diagnostics 

Page 6C1-2–35 

 

Checks Actions 

Fuel System 

• 

Check the fuel system for the following fault conditions. Refer to 6C Fuel System 
– V6. 

− 

restricted fuel filter, 

− 

incorrect fuel pressure, and 

− 

contaminated fuel. 

• 

Check the operation of the fuel injectors. Refer to 6C1-3 Engine Management – 
V6 – Service Operations. 

• 

Perform the fuel injector balance test, refer to 6.3 

Fuel Injector Balance 

Test in this Section. 

• 

Check the items that cause an engine to run rich. 

Ignition System 

• 

Inspect for moisture or corrosion around the spark plug and ignition coil area.  

• 

Test the ignition coil voltage output. Refer to 6C1-3 Engine Management – V6 – 
Service Operations. 

• 

Remove and inspect the spark plugs. Refer to 6C1-3 Engine Management –V6 – 
Service Operations. 

N O T E  

If the spark plugs are fouled, determine the cause of the fouling before 
replacing the spark plugs. Refer to 6C1-3 Engine Management – V6 – 
Service Operations. 

• 

Check for loose ignition coil grounds. 

Engine Mechanical 

• 

Parasitic load on the engine such as the following: 

• 

automatic transmission fault condition, or 

• 

a belt driven accessory fault condition. 

• 

Check for the following engine fault conditions. Refer to 6A1 Engine Mechanical –
V6. 

• 

low compression, or 

• 

worn valve train components. 

When all diagnosis and repairs are completed, check the system for correct operation. 

5.13  Surges / Chuggles 

Description 

With the accelerator pedal in a steady position, the vehicle speeds up and slows down or the engine power fluctuates. 

Checks Actions 

Preliminary 

Perform the preliminary checks. Refer to 4.3 Preliminary Checks in this Section. 

Sensor / System 

• 

Using Tech 2, check the heated oxygen sensor (HO2s) operating parameters. 
The HO2s should respond quickly to different throttle positions. 

• 

Test the resistance of the crankshaft position (CKP) sensor. The CKP sensor 
resistance must be 700 – 1,200 

Ω at all temperatures. 

Engine Management – V6 – Diagnostics 

Page 6C1-2–36 

 

Checks Actions 

Fuel System 

• 

Check the fuel system for the following fault conditions. Refer to 6C Fuel System 
– V6. 

• 

restricted fuel filter, 

• 

incorrect fuel pressure, and 

• 

contaminated fuel. 

• 

Check the operation of the fuel injectors. Refer to 6C1-3 Engine Management – 
V6 – Service Operations. 

• 

Perform the fuel injector balance test, refer to 6.3 

Fuel Injector Balance 

Test in this Section. 

• 

Check the items that cause an engine to run rich. 

• 

Check for fault conditions that can cause an engine to run lean. 

Ignition System 

• 

Inspect for moisture or corrosion around the spark plug / ignition coil area. 

• 

Test the ignition coil voltage output. Refer to 6C1-3 Engine Management – V6 – 
Service Operations. 

• 

Remove and inspect the spark plugs. Refer to 6C1-3 Engine Management – V6 – 
Service Operations. 

N O T E  

If the spark plugs are fouled, determine the cause of the fouling before 
replacing the spark plugs. Refer to 6C1-3 Engine Management – V6 – 
Service Operations. 

• 

Check for loose ignition coil ground circuit. 

Additional Checks 

• 

Check the torque converter clutch (TCC) operation. A TCC that applies too soon 
can cause engine detonation, which will trigger spark retard activity. Refer to 7C2 
Automatic Transmission – 4L60E – Electrical Diagnosis. 

• 

Test the A/C clutch for correct operation. Refer to 2A Heater and Air-conditioning.

• 

Check the evaporative emission (EVAP) canister purge solenoid for the following 
conditions: Refer to 6C1-3 Engine Management – V6 – Service Operations. 

− 

stuck open condition, and 

− 

charcoal contamination. 

• 

Check the exhaust system for possible restrictions. Refer to 6F Exhaust System – 
V6. 

• 

Electromagnetic interference (EMI) on the crankshaft position (CKP) sensor can 
cause an engine misfire condition.  

 

Using Tech 2, monitor the engine speed parameter. A sudden increase in the 
engine speed parameters without moving the throttle position indicates that an 
Electromagnetic Interference fault may be present.  

 

Wiring harness routing which may be positioned very close to a high voltage or 
high current device such as the following may induce EMI: 

• 

secondary ignition components, or 

• 

motors and generators. 

When all diagnosis and repairs are completed, check the system for correct operation. 

Engine Management – V6 – Diagnostics 

Page 6C1-2–37 

 

6 Functional 

Checks 

6.1 General 

Information 

The items detailed in the following pages are to be used when there is a customer complaint and there are no diagnostic 
trouble codes set, or one or more of the Tech 2 data values are not within the typical values. They are also to be used 
when instructed from a DTC table. Before using these tables, you should refer to 5  Symptoms Diagnostics in this 
Section, which may direct you to using the following functional checks. 

The purpose of these tables is to diagnose engine control module (ECM) controlled components or sub-systems that do 
not have diagnostic trouble codes assigned to them. Another purpose of these tables is for Technicians who feel 
confident that a particular part of the sub-system is not operating properly and wants only to check that particular item 
for proper operation without going through lengthy diagnostic procedures. 

6.2 

Fuel Injector Coil Test 

The fuel injector coil test is divided into two parts. Begin by performing the fuel injector coil quick test. Then only perform 
the Injector Coil Test – With Special Tool J39021 procedure if the quick test determines that there is a faulty fuel injector. 

Fuel Injector Coil Quick Test 

Test Description 

The following numbers refer to the step numbers in the diagnostic table: 

1 

This step checks if the engine coolant temperature is within the correct range. 

2 

This step tests each fuel injector resistance within a specific temperature range. 

3 

This step determines if all of the fuel injectors are within 3 ohms of each other. 

Step Action  Value(s) 

Yes 

No 

1 

Using Tech 2, observe the engine coolant temperature 
(ECT). 

Is the ECT within the specified range? 

10 – 32

°C

Go to Step 2 

Go to Step 3 

2 

1 

Disconnect the fuel injector harness connector, 
refer to 2.13 Fuel Rail Assembly, in 6C1-3 Engine 
Management – V6 – Service Operations. 

2 

Using a digital ohmmeter and connector test 
adaptor kit J 35616-A, measure the resistance of 
each fuel injector between the ignition voltage 
circuit and the fuel injector control circuit. Refer to 
8A Electrical - Body and Chassis for information 
on testing for continuity and to Figure 6C1-2 – 9 
and Figure 6C1-2 – 10 for the fuel injector 
harness connector. 

Do any of the fuel injectors display a resistance outside 
the specified range? 

11 – 14 

Ω

Refer to Injector 
Coil Test – With 

Special Tool J39021 

in this Section 

Injectors OK