Engine Management Overview

Engine management and exhaust emission is controlled by the ECM, which has the following main functions:
- Fuel injection
- Idle speed
- Ignition
- Evaporative loss system
- Engine cooling fans
- Climate control compressor clutch demand

The microprocessor within the ECM receives signals from various sensors and other modules and uses a predetermined program to compute engine management functions.

Adaptive functions are incorporated in the ECM to cater for continuous adjustments to its computations to suit prevailing conditions. Because the system also controls emissions to suit all modes, neither CO levels or idle speed require service attention or adjustment, except of course should an error occur.

On Board Diagnostics are controlled by the ECM with the continuous monitoring of incoming signals and the subsequent verification against what the module expects to "see." Should a signal be incorrect or missing the ECM will substitute a fixed value to provide the "limp home mode" and alert the driver of the problem. Fixed values may be adopted for
- Transmission oil temperature
- Mechanical guard position
- Throttle blade angle
- Camshaft position
- Intake air temperature

Diagnostic trouble codes are stored in the ECM memory to be subsequently read by an appropriate retrieval tool.

NOTE: Should either the ECM or TCM fail, please ensure that the control housing cooling fan is operating correctly. Failure of the cooling fan MUST be rectified before renewing a control module and details of a fan failure should accompany a returned control module.

NOTE: The ignition supply is the main power source for the ECM; this supply will be disconnected by an inertia switch if the vehicle is subject to a violent deceleration, as in a collision. The ECM has separate ignition and battery supply inputs. The battery input maintains the ECM memory as long as the vehicle battery is connected.

ECM Input Signals

ECM Input Signals:

1 Engine Speed
2 Ignition Amplifier Failure
3 Cranking
4 Camshaft Position
5 Mass Air Flow
6 Intake Air Temperature
7 Coolant Temperature
8 Exhaust Gas Oxygen Content
9 Knock Sensor
10 Power Supply
11 Climate Control Compressor
12 Climate Control System Pressure
13 Traction Control
14 Park / Neutral Switch
15 Throttle Pedal Demand
16 Throttle Position
17 Security Mode

ECM Output Signals

ECM Output Signals:

1 Exhaust Gas Recirculation (Discontinued for USA during 1997 production)
2 Purge Valve
3 Engine Torque Reduction
4 Electronic Throttle Assembly
5 Cooling Fans
6 Ignition Amplifier Driver
7 Engine Overspeed
8 Climate Control Compressor Clutch
9 OBD II Information (J1962, CAN, ISO)
10 Fuel Pump Relay
11 Heated Oxygen Sensor
12 Variable Valve Timing
13 MIL Switching