So Lately, I have been getting a nasty P0107 code --- which correlates to a low input voltage from the barometric sensor.

From my little research, if you are between 0 and 1600' above sea level. the readings that should be coming out of the baro sensor should be between 3.7v and 4.2 volts.

Now I run a ford meter in my evo, where I have a fixed External Temperature compensation of 80 degrees. I have incorporated a potentiometer, to control the output voltage to the ecu, to what I want it to be. In my case, since I live in michigan, with an estimated elevation of 800' above sealevel. I have my Potentiometer outputting 3.8volts.

I have run this set up for about 3 years, without a single issue. All of a sudden, the car stumbles, afrs are irratic from 10.1 all the way to 19.5 .

what I did to try and fix this is
1) re did the grounds for the potentiometer
2) Replaced the Pot ( I am using a 10k POT)

My question to the community is :
If I want to remove the potentiometer all together, how would I wire in two resistors, to effectively drop the 5V input from the ecu, to a 3.7 V output of a simulated baro sensor.
I don't think it is as simple as placing a resistor in line with the Gray wire (baro input from Ecu) to the Yellow Blue wire ( output from baro sensor to the ecu)

thanks for your help and I hope I was not too confusing in what I want./

 

7k4 and 2k6 resistors, or the nearest combination you can get that gives that ratio.

 

^ thank you

wired this way


from ecu (5.0v) yellow/blue
gray wire (3.7)v (output to ecu)
-------------------{>>>}----------------------
| |
|_______{>>>}____|


where does the ground that would have gone to the pot go ?, or is that no longer required.

 

The resistors go in series between ground and 5V, with the ECU baro input coming from in between the resistors - just like your potentiometer.

The larger value resistor is attached to ground, the smaller value resistor to 5V.

There is a way to do this in the ECU code - I do it in my speed density conversion, but I don't think the conversion has been done for the 8 yet.

 

I understand, thank you, being able to change the baro values in ecu to a static value, would be ideal for me, but I will use the radio shack method, for now.

In your experience, have you ever had any flakiness with Potentiometers ?

This is a first for me that is for sure.( I guess with any electronics, failure is inevitable when placed in the harsh environment of an engine bay.

 

Yes I have had issues, especially when read by digital electronics. The wiper and track can get dusty or contaminated. There are higher quality pots available that might be better. Was it in the engine bay?

I think we've all had issues with volume controls on old equipment getting crackles and channels dropping out? Same issue here.

You'll need to look at the available resistors, what they add up to doesn't have to be exactly 10k, the ratio is critical though, as is the tolerance. The current at 5V through 10k will be 0.5mA. Somewhere between 5k and 10k total would be good.

 

Yes it was in the engine bay, wrapped up in electrical tap, Basically the pot would out put the appropriate value ( 3.8 volts) but the issue with p0107 was very intermitant, therefore I figured that the only likely candidate would be a faulty Pot.

My approach was going to be ohming out between the two terminals of the pot, but the values I was getting were very weird ( maybe I just had the wrong channel recording on the meter) , I was getting 0.7( ohms) or it might have been on (M ohms)

What would u suggest for lockable potentiometers, that are solid state. ? ( do they even exist, or is the resistor method better, since I am not always at different altitudes)

 

I think that wire wound types may be better, best read up on a components website. All the ones I have are UK based, I think the US will have much better choice and prices (as usual ).

 

I will check, thanks for the help , I appreciate it