ECM Adaptions
ECM Adaptions
the ECM 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 IACV
- the TP sensor
- the HO2S
- the MAF/IAT sensor
- the CKP sensor
- Electric throttle body.
HO2S and MAF/IAT Sensor
There are several adaptive maps associated with the fuelling strategy. Within the fuelling strategy the ECM calculates short-term adaptions and long term adaptions. the ECM will monitor the deterioration of the HO2S over a period of time. It will also monitor the current correction associated with the sensors.
the ECM will store a fault code in circumstances where an adaption is forced to exceed its operating parameters. At the same time, the ECM will record the engine speed, engine load and intake air temperature.
CKP Sensor
the characteristics of the signal supplied by the CKP sensor are learned by the ECM. This enables the ECM to set an adaption and support the engine misfire detection function. Due to the small variation between different flywheels and different CKP 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 is renewed or replaced.
the ECM supports four flywheel adaptions for the CKP sensor. Each adaption relates to a specific engine speed range. the engine speed ranges are detailed in the table below:
To set the flywheel adaptions, follow the procedure detailed below. This procedure should be carried out in an appropriate area off the public highway. TestBook/T4 must be connected throughout this procedure. the adaptive speed settings must be read from TestBook/T4 while the vehicle is moving at speed.
1 Use TestBook/T4 to clear any adaptions currently set.
2 With the engine warm (>86°C), select 2nd gear high range.
3 Accelerate the vehicle until the engine speed reaches the limiter.
4 Release the throttle and allow the vehicle to decelerate until the engine idle speed is reached.
5 Check that one of the speed range adaptions has been set (read this from TestBook/T4).
6 Repeat the above procedure until all four adaptions are set
When all four adaptions have been set, check that the ECM has not recorded any misfire detection faults. If it has, then clear the memory of the misfire fault codes.
It may not be possible to reset adaption number 4 if the ECM has already been programmed with a value. Due to the nature of the procedure and the self learn capacity of the ECM, if adaption number 4 does not reset, it is permissible to leave this adaption and let the ECM learn it during normal vehicle usage.
Misfire Detection
Legislation requires that the ECM 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 monitors the number of misfire occurrences within two engine speed ranges. If the ECM detects more than a predetermined number of misfire occurrences within either of these two ranges, over two consecutive journeys, the ECM will record a fault code and details of the engine speed engine load and engine coolant temperature. In addition the ECM 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 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 can detect variations in flywheel speed by monitoring the sine wave signal supplied by the crankshaft position sensor.
By assessing this signal, the ECM can detect the presence of an engine misfire. At this time, the ECM 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 TestBook/T4. the ECM will evaluate the signal against a number of factors and will decide whether to count the occurrence or ignore it. the ECM can assign a roughness and misfire signal for each cylinder (i.e. identify which cylinder is misfiring).