The way I understand the Boost Sensor to work is that the higher the air pressure, the lower the resistance and therefore, the sensor takes the 5v input and exports a voltage based on the changed resistance to the signal wire that goes to the ECU. Correct me if I'm wrong here.

The problem I'm having is I installed a 3 bar MAP sensor and hooked up all the wires to the appropriate pin positions, changed the PFC to option 2 and put in 41800 and offset 0... The Commander and FC Edit is telling me that the PIM voltage is 4.87v... So what this tells me is that the signal wire is coming into the ECU with 4.87v at atmospheric.

So then I disconnected the connector to have the 3 pins in the air and turned the key to on and watched the commander yet again tell me 4.87v. How can this be if they're not connected to anything. It must have a short somewhere.

So I check for continuity between the 5v and the signal pin and there's no continuity.

How can this signal wire go to the ECU with 4.87v if it's not connected to a sensor or the 5v wire?? Can someone help me out?

And also before I get a bunch of replys saying that the power FC settings aren't right, keep in mind that the PFC reads a voltage and uses scale and offset to assign it to a cell. If my scale and offset are off, I might be in N1 P19 instead of N1 P20. The problem is in the wiring I believe and somehow the signal wire is getting 4.87v when it's supposed to have around 0-1 I believe. HELP!!!!!

Thanks,
Richard

 

Just to add some info to the forum. The problem was that the ground for the harness wasn't grounded by the ECU. The Emissions harness connects to the front harness and then grounds, so double check the emissions harness to front harness clip (blue connector).

Richard

PS- The sensor I think works the opposite way as far as the voltage input/output but not sure.

 

Thanks for this. It had me tearing wiring harnesses apart and re-soldering. Since I changed the grounding point (the only variable left) I am sure this is my problem too.

In case anyone else ends up doing a search on it in the future I'll add some key words in here:

PIM voltage max connection problem 4.99 4.0 PFC Apexi Apex'i 3-bar 3 bar map sensor

Tony