I recently bought 2001 Astral 2.0 dti (74 kw engine, 240 000 km) and just changed the oil and filters. Today I went for a short drive on a highway and since the road was clear, I decided to test the car. Everything was fine until I got to about 145 KPH and then engine lost power and service light came on (wrench icon). On this car, check engine light is not coming on at all, but there were no fault codes when they checked during the oil change. I slowed down as soon as I felt the power loss and pulled over by the side of the road. The engine was running just fine. The power loss was an instantaneous one, this wasn't "limp home" mode. I thought that this might have been a broken intercooler hose, but when I opened the hood, I couldn't notice anything wrong. Engine wasn't overheated (in fact it was a bit cold, I think thermostat needs to be replaced). Then I remembered the way to read fault codes by pressing the break and gas pedal at once and turning the ignition on. I switched off the engine, did that and the service light went off, it wasn't blinking to indicate the a fault code. Not knowing what to do, I started the car and did the same thing again - it works well, engine car rev to higher revs in 3rd and 4th, but in 5th gear as soon as it reaches some 145-150 KPH it loses power and service light comes on. Again, this wasn't limp home, the car had plenty of power to go 100+KPH and accelerate. I did the same thing to reset it and it I haven't noticed any other problems. Fuel consumption is normal and I cannot notice any problem with the engine, there's no smoke, it pulls well...
One thing I did notice, at the shop they poured more oil than they should have, the oil level is good 5-6 mm above the maximum line on the dipstick. Could this be a problem?
The previous owner used the car mostly in town, only went for longer trips few times a year. Could it be carbon buildup in EGR?
What could be the cause of check engine light not working at all. These should be LEDs, it's highly unlikely that this particular LED has burned out.