Boost sensor error nightmare! Why does my boost sensor have three power wires?
 

My Rtek 2.0 told me I have a boost sensor error. When I view the sensor output on the palm pilot it reads 15.8 psi all the time. I went to the FSM and followed the boost sensor error troubleshooting and repair section and found out the my boost sensor should have 4 wires going to it; A ground wire, a sensor output signal wire (votage variable dependent on manifold pressure), and two power wires, one 5 volt and one w/ battery voltage.

When I tested the wires coming out of my boost sensor I found that I have battery voltage on the boost sensor output wire. In fact, even if I unplug the boost sensor, there is still full battery voltage on the output wire. I've been trying to figure this boost sensor issue out for a while, so far I have replaced the boost sensor, swapped the ecu for another and even gone so far as to replace the entire egi wiring harness, and still havne't been able to remedy the problem.

If anyone can help me w/ ideas or suggestions please do.

what color are your wires? Do you have a fcd installed?

Most likely your problem is due to putting a turbo engine into a non turbo car.

You Probably used a turbo emissions harness and did NOT make the proper wiring changes to the harness so it would mate with a non turbo convertible harness.

Your problem has a lot to do with two plugs called FEM-01 and FEM-02. FEM stands for front to emissions.

I've written extensively on these plugs. You might try a search using HAILERS as a name and as a topic either FEM-01 or FEM-02 or X-15 or X-16.

Bottom line is your ECU hasn't seen a correct boost sensor reading since you put the turbo in the car. In my humble opinion there are several others out there with the same problem and frankly havn't a clue.

Bottom line is the brown/red boost sensor output is NOW interfacing with a Black/white wire in the FRONT harness. That black/white wire heads right for the ENGINE fuse.

Your could remove the ENGINE fuse then the boost sensor output to the ECU might read right....but the engine won't start.

https://www.rx7club.com/forum/attach...hmentid=142663

The above shows a 87 wiring diagram. It's the X-15 plug that is messing things up. It's called FEM01 on a 88 car. Same wire though.

And think about this. Normally the ECU only sees about three or four volts at pin 2B, but your ECU has been seeing 12vdc for some time. I suppose there are some protection devices in the ECU to protect it from a over voltage like that. I suppose.