For Xmas, I gave my son a PLX DM-5 combo. What attracted me was the fact that I would not have to add a bung but replace the existing sensor and "share it" w/ the gauge and the ECU. The instructions are a little light explanation wise - at least for me (i.e. not the sharpest tool in the shed). It may make more sense to just add a bung and wire up as standalone.

I need help identifying the following wires on the ECU Harness -

1) 12V power
2) chassis GND
3) 02 heater power
4) 02 heater GND
5) 02 signal Input

Appreciate any help you can offer.

 

I don't think you need to do anything with the ECU harness. You will need to figure out the wires on the OEM O2 connector though.

The AM guage (i know, it's different) only needed:

12V (switched, used for heater & to power the meter)
gnd
WOT gnd (used in peak mode)
dat log out
data log gnd

I think your O2 signal input is the one that goes back to the ECU through the OEM O2 connector. I'm sure they'd be glad to help if you gave them a call.

 

The gauge by itself seems clear but having the O2 sensor support is the confusing part. Naive of me to think that one would just splice the old O2 sensor harness into the new one PLX provided.

For example -

From the directions -

1) if the stock O2 sensor has more then two wires then I need to install a 20 Ohm, 10 watt load resistor to prevent engine check code error. This allows your ECU to think that your stock narrowband sensor is still being heated.

Looking down through the engine compartment it appears that the stock O2 sensor has more than 2 wires - 3 actually. Can anyone confirm number of wires?

2) Install noise filtering capacitor across chassis ground and O2 signal input as close as possible to ECU. This eliminates unwanted electrical noise and increases close loop ECU performance.

Since they emphasis several times making connection as close as possible to the ECU, I figured to mount the PLX brain inside the CAI and if the wires I need could be identified in the harness as it enters the ECU then the project might not be so bad.

My gut tells me I will be adding a bung which defeats why I selected PLX but then I am not screwing around w/ resistors or capacitors or cutting up my ECU harness.

Nice gauge, came with everything - resistors, capoacitors, ect...............

 

Another question for you guys is - can I add a bung to my OBX header w/out removing the header?

PLX indicates sensor should be before cat.

 

Yeah, I wouldn't be cutting my ECU harness either. I'd find a dead O2 sensor and splice PLX in, to plug the PLX signal into the harness. Put the Cap & Res where ever it's easest and see how it works. You should twist the O2 sig wire with a ground if you can. That will help cancel any noise it may pick up.

If you add a third bung, you'll probably want to find a shop that has experience welding 304 SS. Other than tht, it shouldn't be problem. I couldn't find anyone around here that would do it and use SS wire. I ended up getting a Magnaflow Cat with two bungs. It isn't mounted yet, but I'm working on it.

 

I'm gonna add a bung and leave the ECU alone.

Today, I did the interior - mounted gauge and got the wires down to the foot well. Tomorrow I hope to add the bung. The last step will be mounting the brain, pull wires thru firewall and tap all cables.

Anyone have a suggestion on which fuse to tap for power?

 

To finish the job, I need to find a power source that can supply 3 AMPS and provides power w/ the key turned to the start/running position.

Can anyone recommend a fuse or a wire to tap?

 

I used F40. I think it's the Park Distance sensor, a 5A switched circuit. I put a 3A Add-a-Circuit in and it's working fine.

 

To answer your question bank #1, 02 sensor has four wires. Two White, one Black, one Grey. That's for an 03 MCS.

 

Well I got it all wired up. Only thing missing is adding the O2 sensor to the header. Friday, I have an appointment to add bung and this project is done.

Once done I will post some pics. The gauge looks great - white faced w/ red led numeric display in the center w/ yellow led running around the circular edge. Ended up mounting inside of a gauge pod even though it was not necessary but wanted to balance w/ the boost gauge.