Like many others with S5 electronically controlled MOP's, my ECU (N353 in an fc3c) is throwing trouble code 27 indicating an issue with the metering oil pump control system. In performing the Mazda FSM diagnostics (pp. D16-18 for those of you with the FSM handy), I have discovered that while I have voltage (1.14-1.18V, to be precise) at pin 2A for the ECU terminal voltage, this voltage does not increase along with acceleration as indicated in the FSM.

In diagnosing this issue, I also pulled the MOP and checked all of the resistance values as indicated in the various threads on this forum. All values are within spec (even shorting across multiple windings as indicated in one thread).

I have also pulled the ECU to visually inspect for the dreaded fried resistor and chip in the upper-left hand corner. There is no visual indication of any malfunction, although admittedly, an electronic test would be preferable to the eye-ball test. (I have not found a way to test using the ECU pins in my searches).

There are a couple of threads on here where people mention having the specific problem that I do, but no one ever seems to have solved the problem without simply replacing the ECU and MOP (which is getting ever more difficult and expensive as the years pass).

My question is, has anyone ever isolated the actual problem when voltage remains constant at PIN 2A? I would assume there is some issue with the position sensor on the MOP, but it seemed to check out when I pulled it. Since replacing the relevant components could cost somewhere in the neighborhood of 25% of the total value of the car, I would prefer diagnose the specific problem rather than simply purchasing replacement components of unknown origin and condition. My only other real alternative is to go rtek 1.0, but I would rather maintain proper operation of the oil-injection system if possible.

Thanks in advance for any ideas/help.

 

Alternatively, if no one has any information about the above, does anyone know how to test the MOP-related circuits on the ECU electrically? If I have to go Rtek, I'd at least like to verify that my ECU is okay first.

(Still open to info regarding the original question if anyone new sees this.)

Thanks.