U1203 Engine Error Code
When you check engine light came on code U1203 the reason should be Engine Light ON (or Service Engine Soon Warning Light). However your vehicle's manufacturer may have a different definition for the U1203 OBD-II Diagnostic Network (U) Trouble Code. So you should chech it on your car models.
Reason For U1203
U1203 OBD2 reports a sensor fault, replacement of the sensor is unlikely to resolve the underlying problem. The fault is most likely to be caused by the systems that the sensor is monitoring, but might even be caused by the wiring to the sensor itself.
U1203 OBD-II Diagnostic Network (U) Trouble Code DescriptionU1203 SCP (J1850) Invalid or Missing Data for Windows so you have to check ODB-II Engine Error Code list.
U1203 Code Review :The reason of U1203 OBD-II Engine Error Code is U1203 SCP (J1850) Invalid or Missing Data for Windows.
How To Recognise U1203
The most likely cause of this is that there is no refrigerant left in your system. This could be caused by a leak in your system somewhere, which will have to be fixed before refilling the refrigerant. If you're car-savy and you own a set of air conditioning gauges, refilling the refrigerant is usually easy to do yourself. However, if you're not so confident, enlist the help of a knowledgeable friend or take a quick trip to the mechanic.