The engine oil level checking was modified in Oct 1987.
Previously the oil check light went out after the engine had been started (even with low oil level). To improve this the control unit for central warning was modified to the following:
1. Oil level light stays on in combination with the central warning light, if low oil level exists.
2. If the reset button is pushed, only the central warning light can be turned off. If a low oil level exists, the oil level control light stays on.
3. The oil level warning light in the combi-instrument remains on until the low engine oil level is corrected.
Part No. of Control Unit: 928.641.602.05, this unit can be installed as of Model year 1984.