Isuzu KB P190. Manual - part 814

Engine Management – V6 – General Information 

Page 6C1-1–14 

 

Throttle Body Relearn Procedure 

The ECM stores values that include the lowest possible TP sensor positions (zero percent), the rest positions (seven 
percent), and the spring return rate. These values will only be erased or overwritten if the ECM is reprogrammed or if a 
throttle body relearn procedure is performed. 

N O T E  

If the battery has been disconnected, the ECM 
performs a throttle body relearn procedure once 
the battery has been reconnected and the ignition 
turned on. 

The ECM performs a throttle body relearn procedure anytime the ignition is turned on and the following conditions have 
been met: 

• 

The engine has been off for greater than 29 seconds, 

• 

The engine speed is less than 40 rpm, 

• 

The vehicle speed is 0 km/h, 

• 

The engine coolant temperature (ECT) is 5 – 60°C; if Tech 2 is used to perform the relearn procedure, the ECT is 
5 – 100°C, 

• 

The intake air temperature (IAT) is greater than 5 – 60°C; if Tech 2 is used to perform the relearn procedure, the 
IAT is 5 – 100°C, 

• 

The APP sensor angle is less than 15 percent, and 

• 

Ignition voltage is greater than 10 V. 

The throttle body relearn procedure is performed 29 seconds after the ignition is turned on. The ECM commands the 
throttle plate from the rest position (seven percent open) to full closed (zero percent), then to around 10 percent open. 
This procedure takes about six – eight seconds. If any faults occur in the TAC system, a DTC sets. At the start of this 
procedure, the Tech 2 TAC Learn Counter parameter should display 0, then count up to 11 after the procedure is 
completed. If the counter did not start at 0, or if the counter did not end at 11, a fault has occurred and a DTC should set. 

TAC System Default Actions / Reduce Power Modes 

The ECM switches to the following reduce power modes if the ECM detects a fault condition in the TAC system: 

• 

If an APP sensor circuit fault or TP sensor circuit fault is detected, the ECM limits engine torque so the vehicle 
cannot reach speeds of greater than 100 km/h. The ECM remains in this reduce power mode during the entire 
ignition cycle, even if the fault is corrected. 

• 

If there is a fault condition with the throttle actuator control circuits, a throttle actuator command vs. actual position 
fault, a return spring check fault, or a TP sensor one circuit fault, the ECM limits engine speed to 2500 rpm and 
three – six fuel injectors are randomly disabled. At this time the reduce power indicator is commanded on. The 
ECM remains in the reduce power mode during the entire ignition cycle even if the fault is corrected. 

N O T E  

If a TP sensor one or throttle actuator control 
circuit fault is present at the time the vehicle is at 
idle, with no accelerator pedal angle, the engine 
may stall. 

Forced Engine Shutdown 

A further safety feature which is built into the TAC system is the ECM will initiate an engine shut down if, the ECM’s 
internal monitoring functions detects a serious internal fault, the fuel injectors will be turned off. 

3.6 

Cruise Control System 

The cruise control system integrates with the engine control module (ECM) through the powertrain interface module 
(PIM), to control the electronic throttle actuator and maintain the vehicle at the speed set by the driver.  

Engine Management – V6 – General Information 

Page 6C1-1–15 

 

When the cruise control ON-OFF switch, located on the right hand side of the dash panel, is pressed, the PIM, on 
receiving the input from the switch, turns on the cruise ON-OFF switch warning lamp to inform the user that the cruise 
control has been engaged. 

When the cruise control switch assembly is pressed to SET/COAST, the PIM on receiving the input, sends a signal via 
the serial data bus to the ECM. Providing the pre-conditions for cruise control operation have been met, the ECM 
activates cruise control and commands the PIM to turn on the instrument cluster cruise set warning lamp, to inform the 
user that cruise control is active. The ECM receives all the various inputs required to maintain the correct speed and then 
controls the throttle plate depending on the load on the engine (ascending or descending hills, etc). 

The cruise control is deactivated by either pressing the brake pedal, clutch pedal, cruise CANCEL or by the cruise control 
ON-OFF button. In each of these instances, the ECM receives an input when any of these switches are activated. For 
further information on the cruise control system, refer to 8C Cruise Control – HFV6.  

3.7 

Brake Torque Management 

Brake torque management places limits on engine torque when the brakes are applied, regardless of the accelerator 
pedal position (APP). The conditions under which brake torque management occur are as follows: 

• 

The accelerator has been depressed before the brakes are applied, 

• 

The brakes are applied and the ECM receives an input from the stop lamp switch, 

• 

Vehicle speed is greater than 5 km/h, 

• 

Engine speed is greater than 1200 rpm and 

• 

Conditions exist for greater than 2.5 seconds. 

When brake torque management has been implemented, the torque is reduced by altering the throttle plate opening by 
25%. The ECM will monitor the rate at which the vehicle is slowing and adjust the throttle plate opening accordingly. 

3.8 

Emission Control Systems 

Evaporative Emission Control System 

The evaporative emission control system used is the 
activated carbon (charcoal) canister storage method. Fuel 
vapour is drawn from the fuel tank into the canister where it 
is held by the activated carbon until the ECM commands the 
evaporative emission (EVAP) purge solenoid valve to open.

The ECM energises the EVAP purge solenoid valve by 
applying a pulse width modulated (PWM) ground to the 
EVAP purge solenoid valve control circuit.  

Figure 6C1-1 – 9 

Engine Management – V6 – General Information 

Page 6C1-1–16 

 

When ECM commands the EVAP valve (1) to open, the fuel 
vapours are drawn from the canister line (2) into the intake 
manifold where it is consumed in the normal combustion 
process. 

 

Figure 6C1-1 – 10 

The ECM energises the EVAP valve when the appropriate conditions have been met, such as: 

• 

Engine coolant temperature is less than 20

°C at cold start up and the engine has been running longer than 

three minutes and 10 seconds, or 

• 

Engine coolant temperature is greater than 80

°C and the engine has been running longer than five seconds, or 

• 

Engine is not in decel fuel cut-off mode and the throttle opening is less than 96%, or 

• 

The engine is in closed loop fuel mode. 

A higher purge rate is used under conditions that are likely to produce large amounts of vapour, when the following 
conditions have been met:  

• 

Intake air temperature is greater than 50

°C, or 

• 

Engine coolant temperature is greater than 100

°C, or 

• 

The engine has been running for greater than 15 minutes. 

The EVAP purge PWM duty cycle varies according to operating conditions determined by mass air flow, fuel trim and 
intake air temperature. The EVAP canister purge valve is re-enabled when throttle position angle decreases below 96%. 
For further information on the evaporative emission control system, refer to 6C Fuel System. 

Engine Ventilation System 

The engine ventilation system contains a Positive crankcase 
ventilation (PCV) valve (1) located in the right-hand 
camshaft cover. A hose is routed from the PCV valve to 
each side of the intake manifold which provides an even 
distribution of crankcase fumes, thereby improving spark 
plug reliability and a reduction in emissions. 

A breather pipe is routed from the intake manifold to the left-
hand camshaft cover and provides fresh filtered air from the 
intake duct to the engine.  

For further information of the engine ventilation system, 
refer to 6A1 Engine Mechanical – V6. 

Figure 6C1-1 – 11 

Engine Management – V6 – General Information 

Page 6C1-1–17 

 

3.9 

Serial Data Communication System 

The engine control module (ECM) communicates directly with the following control units using the General Motors local 
area network (GM LAN) serial data communication protocol: 

• 

Transmission control module (TCM) (if fitted) 

• 

Powertrain interface module (PIM) 

The immobiliser control unit (ICU) communicates directly with the PIM using Keyword 2000 serial data communication 
protocol. Refer to 11A Immobiliser for further information 

As the GM LAN serial data communication protocol is not compatible with the Keyword 2000 serial data communication 
protocol, a powertrain interface module (PIM) is integrated to the serial data communication system to perform the 
following tasks (Refer to 6E1 Powertrain Interface Module – V6): 

• 

Translate the GM LAN serial data transmitted by the ECM into a Keyword 2000 serial data that can be received 
and recognised by the ICU. 

• 

Translate the cruise control switch, automatic transmission power mode switch and 3

rd

 start switch signal into a GM 

LAN serial data that can be received and recognised by the ECM. 

3.10  Self Diagnostics System 

The ECM constantly performs self-diagnostic tests on the engine management system. When the ECM detects a 
malfunction, it also stores a diagnostic trouble code (DTC). A stored DTC will identify the problem area(s) and is 
designed to assist the technician in rectifying the fault. In addition, DTCs are classified as either Current or History DTC. 

Depending on the type of DTC set, the ECM may turn on the 
malfunction indicator lamp (MIL) (1) to  warn the driver there 
is a fault in the Engine Management System. 

Figure 6C1-1 – 12 

3.11  Service Programming System 

The ECM has an Electronically erasable programmable read only memory (EEPROM) where the software and 
calibration information required to operate the engine management system are stored.  

The ECM features a service programming system (SPS) to flash program the EEPROM in the ECM with the latest ECM 
software to provide optimum performance, driveability and emissions control or to program a new ECM. 

Flash programming refers to the SPS used to transfer (or download) ECM data from a computer terminal to the vehicle’s 
ECM. The system is designed so the vehicle verification procedures are required to eliminate EEPROM tampering that 
could increase engine emission levels.  

There are three main flash programming techniques: 

1 

Direct programming (pass through). This is where the vehicle’s data link connector (DLC) is connected directly to a 
computer terminal. On screen directions are then followed for downloading. 

2 

Remote Programming. Reprogramming information is downloaded from a computer terminal to Tech 2. Tech 2 is 
then connected to the vehicle’s DLC. On screen directions are then followed for downloading. 

3 

Off-board Programming. The off-board programming method is used when a re-programmable ECM must be 
programmed while it is removed from the vehicle. For example, an independent repair facility may find it necessary 
to replace a faulty ECM. On flash programming equipped vehicles, the replacement ECM must be programmed 
with data for the specific vehicle identification number (VIN) or the vehicle may not operate properly.