BMW M52TU M54 Fault Codes – P1250, P1188, P1189, P1622 – E36, E46, E39, X5, X3, Z3, Z4
I have a 99 BMW 323i that I just adore, but she needs some help. I have done all of the work on her myself, (OK, with my brothers help), but recently i just came across some error codes that I’m not sure about. Over the last few weeks my engine light has been coming on for a while/going off/ coming on, so i pulled the codes and got 4. They are P1250, P1189, P1188, P1622. The car has had no noticeable change in driving or idling, but as life has perfect timing my inspection is up in a few weeks. I’m hesitant also because I’ve read in some forums that some of these codes (esp 1250 and 1188/9) together refer to a different problems, some say O2 sensors, a fuel pressure regulator, leak in oil drain hose, oil separator, or even a airflow meter! I know anyone would need to see my baby to accurately diagnose her but can you provide me with some direction,as to what i should start checking and what to look for?
The codes (for your 99 323i) are as follows:
P1250 = This is not a valid code for your 99 323i. It may be that you are using a generic OBD-II reader and it can not properly read a BMW proprietary code (as opposed to the DOT mandated generic OBD-II codes). When this happens, the code reader will typically give a false code number.
P1188 = Fuel control, bank-1, sensor-1 (cylinders 1-3, pre-cat O2 sensor)
P1189 = Fuel control, bank-2, sensor-1 (cylinders 4-6, pre-cat O2 sensor)
P1622 = Map cooling thermostat control circuit
With these codes (and ignoring the P1250, for now), we would suggest that you replace the thermostat. While the thermostat code does say control circuit, failure of the electrically controlled thermostats is very common and we would suggest that you start here. The fuel control codes could certainly be a result of the thermostat not functioning properly. After the thermostat is replaced, clear the codes and then see if any reappear. If they do, we can address them.