Hi All,
needing a little help … I don’t have social media so hoping I can get help here before signing up!

I’ve had an issue with my car when getting mapped recently with a “pulse” on the signal wire from MAP sensor back to ECU. At WOT this is a real danger and throwing things off. Obviously mapping was stopped but being an electrical guy I wasn’t paying to have it fixed… don’t doubt the mapper could with time, though he was equally stumped given the condition of the car.

I replaced the sensor after with a known good unit, to no avail.

I’ve back probed the sensor key on engine off (KOEO) and get 5V on the positive, good ground too, but the sensor voltage fluctuates at random between 1.23 and 1.24V. Same when taking reading from ecu plug. I can see this output on the little scan gauge I have too, which jumps between 14.3 and 14.5 PSI (~ 1 bar atmos). It was also viable at time of mapping via the ECUtek sensor voltage plot.

I changed ecu with another of same type/model/part number, which is assumed good as sold as so (little ways to verify this), and the issue remains.

so I’m wondering, does anyone have access to their sensor output, by direct measurement, scanner or onscreen with aftermarket ECU? If you could go to the trouble of checking I’d be most grateful. Not necessarily for the voltage as this is elevation/weather dependant but for a pulse or fluctuation. It happens immediately, continuously, though randomly.

car is 2002 UK sti prodrive, EJ207 and otherwise perfect.

A very frustrating issue, almost like chasing a ghost.

continuity and ohmic readings on wiring is also ok.

I’ve checked the Subaru wiring diagrams and the MAP shares 5V with TPS along with ground, but the coolant temp sensor ground is linked in back to a shielding block. Disconnecting those does not help either…

any help appreciated or further questions should I have missed anything.

thanks in advance!