ECM Adaptions

ECM (Engine Control Module) Adaptions

The ECM (engine control module) has the ability to adapt the values it uses to control certain outputs. This capability ensures the EMS can meet emissions legislation and improve the refinement of the engine throughout its operating range.

The components which have adaptions associated with them are:
^ The APP (accelerator pedal position) sensor
^ The HO2S
^ The MAF (mass air flow) /IAT (intake air temperature) sensor
^ The CKP (crankshaft position) sensor
^ Electric throttle body.

UHEGO/HEGO and MAF/IAT Sensor
There are several adaptive maps associated with the fueling strategy. Within the fueling strategy the ECM (engine control module) calculates short-term adaptions and long term adaptions. The ECM (engine control module) will monitor the deterioration of the oxygen sensors (HEGO and UHEGO) over a period of time. It will also monitor the current correction associated with the sensors.

The ECM (engine control module) will store a fault code in circumstances where an adaption is forced to exceed its operating parameters. At the same time, the ECM (engine control module) will record the engine speed, engine load and intake air temperature.

CKP (crankshaft position) Sensor
The characteristics of the signal supplied by the CKP (crankshaft position) sensor are learned by the ECM (engine control module). This enables the ECM (engine control module) to set an adaption and support the engine misfire detection function. Due to the small variation between different flywheels and different CKP (crankshaft position) sensors, the adaption must be reset if either component is renewed, or removed and refitted. It is also necessary to reset the flywheel adaption if the ECM (engine control module) is renewed or replaced. The ECM (engine control module) supports four flywheel adaptions for the CKP (crankshaft position) sensor. Each adaption relates to a specific engine speed range. The engine speed ranges are detailed in the table below:

Adaptions Engine Speed, rev/min
1 1800-3000
2 3001-3800
3 3801-4600
4 4601-5400

Misfire Detection
Legislation requires that the ECM (engine control module) must be able to detect the presence of an engine misfire. It must be able to detect misfires at two separate levels. The first level is a misfire that could lead to the vehicle emissions exceeding 1.5 times the Federal Test Procedure (FTP) requirements for the engine. The second level is a misfire that may cause catalyst damage.

The ECM (engine control module) monitors the number of misfire occurrences within two engine speed ranges. If the ECM (engine control module) detects more than a predetermined number of misfire occurrences within either of these two ranges, over two consecutive journeys, the ECM (engine control module) will record a fault code and details of the engine speed, engine load and engine coolant temperature. In addition, the ECM (engine control module) monitors the number of misfire occurrences that happen in a 'window' of 200 engine revolutions. The misfire occurrences are assigned a weighting according to their likely impact on the catalysts. If the number of misfires exceeds a certain value, the ECM (engine control module) stores catalyst-damaging fault codes, along with the engine speed, engine load and engine coolant temperature.

The signal from the crankshaft position sensor indicates how fast the poles on the flywheel are passing the sensor tip. A sine wave is generated each time a pole passes the sensor tip. The ECM (engine control module) can detect variations in flywheel speed by monitoring the sine wave signal supplied by the crankshaft position sensor.

By assessing this signal, the ECM (engine control module) can detect the presence of an engine misfire. At this time, the ECM (engine control module) will assess the amount of variation in the signal received from the crankshaft position sensor and assigns a roughness value to it. This roughness value can be viewed within the real time monitoring feature, using T4. The ECM (engine control module) will evaluate the signal against a number of factors and will decide whether to count the occurrence or ignore it. The ECM (engine control module) can assign a roughness and misfire signal for each cylinder, (i.e. identify which cylinder is misfiring).

Diagnostics
The diagnostic socket is located in the fascia, in the driver's stowage tray. The socket is secured in the fascia panel and is protected by a hinged cover.

The ECM (engine control module) stores faults as DTC (diagnostic trouble code), referred to as 'P' codes. The 'P' codes are defined by OBD (on-board diagnostic) legislation and, together with their associated environmental and freeze frame data, can be read using a third party scan tool or T4. T4 can also read real time data from each sensor, the adaptive values currently being employed and the current fueling, ignition and idle settings.