No Voltage to Throttle or MAF after swap

[Sum10clever]

I need help.
After replacing my FA20 with a used built FA20 the engine won’t start.
It cranks but will not turn over.
Codes P0102 (MAF), P0113(MAF), P0123 (Throttle) and P0223 (throttle)
After hours and hours of trouble shooting I’ve discovered there is no voltage coming from the ECU for pins 38 and 39 of the engine harness.

Question 1. Should I only see voltage when cranking or when the Key is in the on position?

Question 2. If I run my own power and ground to the sensor side should I cut loose the side that goes to the ECU or leave it attached?

Question 3. Why the hell did these wire loose power. Before the swap I didn’t have this problem.

The previous owner of the engine blew all his electronics because he did not put the grounds on under the manifold.

I thought the harness attached to the new engine would be safe. Could it have blown a circuit in my ECU?

After all my issues I swapped harnesses from my old engine to the new one. A couple of the sensors didn’t match the plugs so I swapped 2 of my sensors from the old engine. That did not fix it so I spent hours figuring which wires in the harness were power and ground. Now that I found them and they don’t have voltage I really need to know how to proceed.

[Ashikabi]

If you run your own power you should probably cut loose the ones from the ECU. Or just depin them and rig up some shit for testing then you can put everything back depending on results.

Check fuses first. I've fucked with a lot of shit when it was something stupid and easy all along

With your old harness(was good before swap) do you still have no voltage, or are the other sensors holding you up? I would expect the car to start with no MAF. When you say throttle, do you mean throttle body or pedal? Have you checked continuity on your wires between the sensor and the ECU? Maybe it was damaged?

I'm just spitballing ideas. I don't have the answers you asked for, just a bunch of experience fighting with my car

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[Sum10clever]

My suspicion is that the harness that came with the engine was damaged somehow or the sensors that had to be changed to fit the new harness somehow messed up me ECU. There are not any fuses to check because they go straight from the ecu to the harness and then from the harness to the MAF and throttle body (not the throttle pedal). I forgot to mention I am getting 3 ohms of resistance from battery ground to the - wire in the harness and the same on the + wire. I believe it should be .01 ohms or less.

[Ashikabi]

Originally Posted by Sum10clever

My suspicion is that the harness that came with the engine was damaged somehow or the sensors that had to be changed to fit the new harness somehow messed up me ECU. There are not any fuses to check because they go straight from the ecu to the harness and then from the harness to the MAF and throttle body (not the throttle pedal). I forgot to mention I am getting 3 ohms of resistance from battery ground to the - wire in the harness and the same on the + wire. I believe it should be .01 ohms or less.

Bad ground? Or the resistance is weird because it runs through the ECU and the car is off. What's your resistance when you measure from the pin at the ECU to the pin at the sensor?

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[Sum10clever]

Ok update. A Subaru technician said that there shouldn't be any voltage from those wires until the pedal is pressed to open the throttle. He did say that my pin 3 should be a ground and it is not showing ground so my next step is to ground that wire and see what happens. However when I look at the wiring diagram it does not show pin 3 as a ground it shows a symbol that looks like this ~ which I believe is a fuse symbol but not sure. Any ideas guys? And thanks for the replies.

[Ashikabi]

Originally Posted by Sum10clever

Ok update. A Subaru technician said that there shouldn't be any voltage from those wires until the pedal is pressed to open the throttle. He did say that my pin 3 should be a ground and it is not showing ground so my next step is to ground that wire and see what happens. However when I look at the wiring diagram it does not show pin 3 as a ground it shows a symbol that looks like this ~ which I believe is a fuse symbol but not sure. Any ideas guys? And thanks for the replies.

Sounds like a fuse to me. Or the wire continues off the page? Are wires 1or2a ground? It won't have 2 grounds

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