I got a HP 500 EFI from the year of 2000 who startet to throw the DTC 34 fault code (MAP sensor, low signal voltage).
I've checked the MAP plug and the wiring harnes without any faults. When I check the MAP sensor voltage (gray and black wire) at the plug end I can only meassure 0.15 volt, way below the 5 volts it's supposed to be.
From what I can understand it seems like the ECU doesn't deliver the supposed 5 volts to the MAP sensor.

Is this a ECU malfunction? What to do now?

From my understanding, if I can pick up a 5 volt signal from an other source, for example from the seriel data wire and connect a jumper wire between this 5 v source and the MAP sensor to supply it with 5 volts it should work again. But is this a safe temporary fix?

If you have or can get a wiring diagram I would do a pin check. Pin check is checking the resistance between the MAP plug and plug at ECU.

It's already checked and everything is ok.