HELP WITH 99 BMW 540I

A code P0028 is a thermostat code, meaning that the thermostat is preventing the car from warming up properly. It is most commonly caused by a worn out or stuck open thermostat. The repair is to replace the thermostat. I would check the fuel pressure and spark and then go from there. What does the data stream show? Are you getting an rpm signal, are you getting a data stream? If you are not getting a data stream then you may have accidentally erased some programming. Can you clear the EWS code? If you are still at a loss, tow the car to a good German car shop that has the GT-1 BMW scan tool and get the car re-programmed.

Brian, First, the Launch isn't the tool to get deep into the Bimmer's brain. The EWS (Immobilizer) and DME (ECM) has to be synchronized since there is no start authorization now. I don't know if there is a way to do that with the Launch, I hope, otherwise it has to be towed to a shop who has GT1 or Autologic with BMW software. The other thing, if this has the electrical thermostat, disconnect the connectors from the DME and check the top of it for antifreeze residue. It can travel up through the thermostat wiring and eats up the DME's connecting pins and damage the connectors also. It could cause various drive ability issues. I replaced several DME and wiring harness because of this problem. Make sure there is no coolant residue at all on the DME and in the wiring harness. Zee