on Opel / Vauxhall eight-valve engines from 1987 to 1990, Alfa Romeo and some PSA Peugeot Citroën XU9J-series engines. Fuel enrichment during cold-start is achieved by altering the timing of the main injectors based on engine temperature, no "cold start" injector is required. The idle speed is also fully controlled by the Motronic unit, including fast-idle during warm-up (therefore no thermo-time switch is required). The ML4.1 system did not include provision for a knock sensor for timing adjustment. The ignition timing and fuel map could be altered to take account of fuels with different octane ratings by connecting a calibrated resistor (taking the form of an "octane coding plug" in the vehicle's wiring loom) to one of the ECU pins, the resistance depending on the octane adjustment required. With no resistor attached the system would default to 98 octane. There is a single output for the injectors, resulting in all injectors firing simultaneously. The injectors are opened once for every revolution of the engine, injecting half the required fuel each time. Motronic ML4.1 was used in the Opel engines: 20NE, 20SE, 20SEH, 20SER, C20NE, C30LE, C30NE. 4.3 The Motronic 4.3 was used by Volvo for their five-cylinder turbocharged 850 models from 1993 until 1996. It was introduced with the launch of the 850 Turbo (also called the 850 T-5 and 850 T-5 Turbo) in October 1993 for model year 1994. Features included OBD I diagnostics, dual knock sensors and a lot more. For the 1996 model year OBD II diagnostics were introduced on some cars while M4.3 was beginning to be phased out. The last M4.3 equipped cars were made for model year 1997. 4.4 The Motronic 4.4 was used by Volvo from 1996 until 1998. The M4.4 was based on its predecessor and featured only a small number of improvements. Memory capacity was doubled and a few new functions were introduced such as immobilizer compatibility. OBD II was standard on all cars fitted with this system albeit the necessary protocols were not integrated for all markets. The system was used for the five- and six-cylinder modular engined cars and was used on turbocharged and naturally aspirated models. Introduced in 1996 for 1997 model year it was first installed on some of the last 850 models like the 2.5 20V and AWD. A coil on plug variant existed for the six cylinder Volvo 960/S90/V90. After the 850 was replaced by