Hondata

Hi guys:

We have a strange situation with 2 USDM P28's with the S300 unit. For some strange reason, these two ecu's will start up the vehicle for about 8-10 minutes, but will not activate the cooling fans and after such a period of time the engine shuts off by itself. In addition the engine runs lean with these two ecu's when in fact ths vehicle was fully tuned and did not have such a problem. I have taken a visual look inside these two ecu's to see if anything is fried, but all looks perfect. I tested one of the S300 units in a customers P28 and it worked fine, so that probably proves that the S300 is fine. We get no check engine lights whatsoever. I was wondering what is the function of the 74HC373. 20 pin chip. Could this by any chance be causing this problem? I am going to cut the J1 jumper off of both of them and test them on a car to see what happens.
Its not the vehicle because we have a P28 with an S200 unit and it started up fine with no problems, cooling fans engaged as normal, did not shut down and air fuel was as should.

Any insight will be appreciated.
Has this happened to anyone before?

Regards,
Mark Perez
Import Performance

P28 does not control cooling fans. It is controlled by the ECT switch in the water neck. Can't help with the other stuff.

smracing wrote:P28 does not control cooling fans. It is controlled by the ECT switch in the water neck. Can't help with the other stuff.

That is correct. That is why this is a strange situation. When i connect these 2 P28 ecu's the fans do not come on, air fuel gets lean and in about 8-10 minutes the engine shuts off by itself. When i install a P28/S200 unit that we have laying around here, everything functions perfectly. All his problems started when his battery went bad and then he had to change out the alternator as well.

Datalog when the car is running and check the battery voltage. Keep an eye on this when the car dies. Review the entire datalog for anything strange, especially when it dies.