Engine management system - Td5 (Operation): Description and operation

Operation

Engine management

The ECM controls the operation of the engine using stored information within its memory. This guarantees optimum performance from the engine in terms of torque delivery, fuel consumption and exhaust emissions in all operating conditions, while still giving optimum driveability.

The ECM will receive information from its sensors under all operating conditions, especially during: l Cold starting. l Hot starting. l Idle. l Wide open throttle. l Acceleration. l Adaptive strategy. l Backup strategy for sensor failures.

The ECM receives information from various sensors to determine the current operating state of the engine. The ECM then refers this information to stored values in its memory and makes any necessary changes to optimise air/fuel mixture and fuel injection timing. The ECM controls the air/fuel mixture and fuel injection timing via the Electronic Unit Injectors (EUI), by the length of time the EUI's are to inject fuel into the cylinder. This is a rolling process and is called adaptive strategy. By using this adaptive strategy the ECM is able to control the engine to give optimum driveability under all operating conditions.

During cold start conditions the ECM uses ECT information to allow more fuel to be injected into the cylinders, this combined with the glow plug timing strategy supplied by the ECM facilitates good cold starting.

During hot start conditions the ECM uses ECT and FT information to implement the optimum fuelling strategy to facilitate good hot starting.

During idle and wide open throttle conditions the ECM uses mapped information within its memory to respond to input information from the throttle pedal position sensor to implement the optimum fuelling strategy to facilitate idle and wide open throttle.

To achieve an adaptive strategy for acceleration the ECM uses input information from the CKP sensor, TP sensor, ECT sensor, MAP/ IAT sensor, and the FT sensor. This is compared to mapped information within its memory to implement the optimum fuelling strategy to facilitate acceleration.

Immobilisation system When the starter switch is turned on, the BCU sends a unique security code to the ECM. The ECM must accept this code before it will allow the engine to operate. If the ECM receives no security code or the ECM receives the incorrect security code, then the ECM allows the engine to run for 0.5 seconds only. During this operation all other ECM functions remain as normal.

The ECM operates immobilisation in three states: l 'New.' l 'Secure'. l 'No Code'.

When an ECM is unconfigured it will operate in the 'New' state. When an unconfigured ECM is installed the engine can be started and operated once only, then the ECM has to be re-configured to either 'secure' or 'no code' configuration depending on whether a security system is fitted to the vehicle. This is achieved by using TestBook.