Civic EG

I've got a 1995 Civic EX MT. I am getting a reading of .0135V DC output on D19 of the ECM/ECU to the reference / input side of the MAP sensor which is expecting 5V. I have tried 3 ECUs (2 P28s and a P06) and they all read the same voltage. What would cause low voltage on D19? I have cleaned the ground on the thermostat housing. Are there other grounds to investigate? Battery is fully charged.

The ECU is outputting that small of voltage straight from the pin? What about other 5V sources, does your meter read 5v?

It is actually .135V. I believe I am getting similar low readings from many of the connectors on C101. What other sensor should I check for reference? I 'backprobed' (don't actually have small enough probes, I shaved the sleeve and took the reading about 2 inches from the ECU harness) D19 to confirm there was no short between ECU and MAP sensor.

Ok I measured the pins on C103, ECU side.

The connector is numbered like this. I am assuming the clip is on the top in this diagram even though it is mounted in the car with the clip towards the ground.

04 = .057V
05 = .168V
06 = .164V
09 = .168V
12 = .055V
13 = .168V
14 = .168V

MAP sensor still has ~.135V

Battery (between posts) has 13.85 with key off and 13.48 key on. I'm preparing to test with another battery.

edit: Tested another battery, still .135V @ MAP. Need to get another reading at the back of C19, see if it's closer to the C103 readings, I believe it is.

What about the white/blue going into the ECU? Is that getting the full 12 volts? That wire goes to the "backup" fuse on the under hood fuse box.

There are several reference grounds on the ECU. Most go to the thermostat housing but I seem to remember a cluster of grounds on each side under the dash. Check the resistance on these ground wires (disconnect them first) or try grounding the pins directly to the chassis temporarily and see if that fixes the readings.