- Overheated stepper ECU # 9684 ***
I connected a MAC pneumatic solenoid (rated 5.4W@12V) to use with boost control just yesterday.
I connected it to stepper output A and tested the output at 25Hz/50% and it worked and sounded just fine. I base tuned the car on the dyno for 30 mins with solenoid pneumatically disconnected and wastegate forced open with compressed air.
When it was time to use the solenoid it turned out it did nothing and would not actuate. I now discovered I had forgotten to invert the output to maintain normally open position, which meant it had drawn (measured) 0.5A all the time I had the ignition on. Solenoid was was warm to the touch.
In addition, now the P259 low current outputs did not work either and I measured ECU current demand to 240 mA, so I moved relay functions to free injector outputs. ECU configuration is 6+2 so I had only two injector outputs and used one for boost control solenoid and the other for fuel relay, the coolant fan relay we simply grounded the signal to the relay permanently to finish the tuning on the dyno.
Probably the +5V regulator on board is overloaded due to damaged circuits?
The engine is a Toyota 1JZ with Hall sensor triggers and passive coils. A really simple setup that uses a universal harness with solid ground in the welded roll cage (drift car).
What else could cause the stepper output to stop working (and P259) ?
The car has run flawlessly last year, with manual boost pressure regulator.