Edgar Ghazaryan

2003 bmw e60 530d automatic transmission (300.000 km). Im starting to notice
that when heater is on and even when sometimes off, when changing gears
rpm drops two times instead of one.
We plugged in computer two times and no trasmission errors, we got maf sensor error tho and many other errors due to low battery.
It dont happens all the time and it happens more with heater on and while cruising low speed.

tstiglich

Has your transmission ever been serviced? If not, it is long overdue.

Edgar Ghazaryan

last owner actually killed the transmission and bought a used one like 4 years ago

tstiglich

I am guessing that he never serviced the previous one, or the one which replaced it. If you do not know its history, it is long past due for a service.

Edgar Ghazaryan

i mean when they swapped them they inspected the good one. Maybe this problem could be worn out converter pehaps ?

tstiglich

Could be anything. I would start by changing the transmission fluid. Four conical sleeves, and bridge seal.

Edgar Ghazaryan

I hoped it was maf sensor, but it seems you are prone to transmission

tstiglich

I am not trying to imply that will fix your problem, rather I am saying that many transmission problems are often due to lack of service. If you are planning on keeping your car for a long time, I would have it serviced ASAP. I really can't see what the heater would have to do to the performance of the transmission. I assume that shifting is performed as a function of engine load, so it could well be a MAF sensor problem. If you have a low battery, I would replace it, as these cars do not respond well to low battery conditions.