Alternate Rear O2 wiring configuration

busterhax · **Joined:** Wed Jan 22, 2014 6:54 pm **Posts:** 1773

Finally had time to play with my car for the first time in a while.

I got it the cheap GM map sensor all hooked up and working fine.
On the e36, there is a 5v signal coming off of the cruise control plug which is easier to cleanly splice into than it is to splice the TPS plug.
I then chassis grounded the sensor and sent the signal line directly into the o2 plug signal wire. Really simple.

Don't forget to apply the min/max voltage settings in your bin.

mrf582 · **Posted:** Wed May 17, 2017 8:49 pm

ba114 wrote:

I have that exact one on the way too. The first one I bought seems to have died now. It's no longer registering changes in pressure.

New sensor tested working

mrf582 wrote:

Yes, IIRC the ECU only polls the rear O2 sensors every 100ms. It's quite slow, I agree. Alec found there are several threads that respond to varying time delays. Some are 10ms versus 100ms etc. Hopefully in the future we could have it poll every 10ms (instead of 100ms).

Hence why any input from the rear O2 sensors (for the moment) should only be used as a reference.

Yep front o2s are 10ms, rear o2 are 100ms. From memory, with single channel o2 control bit, it was confirmed that if you keep a sensor plugged in, then the code will factor it in calculations correct? if we can identify a way to still use the spare primary o2 bank input for MAP or AFR type logic that would be beneficial.

From what I remember, the single channel option only uses Bank 1 sensors regardless of if you have Bank 2 sensors plugged in. What you may be thinking of is the DTC for the Downstream O2 sensors (Heater and Voltage). They will still trigger a Cat Efficiency code if left plugged in. But if you're using the ECU in Single Channel mode, I would think you should be able to log with Bank 2 sensor wiring (Upstream or Downstream) and have it work without interference.

Kyle, nice to know about the Cruise Control plug having a 5V line. That should make wiring much nicer.

busterhax · **Joined:** Wed Jan 22, 2014 6:54 pm **Posts:** 1773

An update. After some logging I think I have some noise. Ba might be experiencing the same thing.

At max boost(10psi) my logs fluctuate between 7psi and 10psi. I don't really have time to experiment on fixes at the moment but good for thought before going through with this mod.

ba114 · **Joined:** Wed Oct 21, 2015 2:36 am **Posts:** 980

Yep the noise makes it annoying.
PLX recommend bridging a 0.1uF 50V capacitor as close to the dme as possible to help reduce unwanted noise. I found this in their WBO2 instructions. I'm going to try it on mine to see if it has a positive effect.

busterhax · **Joined:** Wed Jan 22, 2014 6:54 pm **Posts:** 1773

ba114 wrote:

Yep the noise makes it annoying.
PLX recommend bridging a 0.1uF 50V capacitor as close to the dme as possible to help reduce unwanted noise. I found this in their WBO2 instructions. I'm going to try it on mine to see if it has a positive effect.

I'm guessing one end on the 0-5v side and one end on the ground side? I think I have one lying around that I could try out today or tomorrow.

ba114 · **Joined:** Wed Oct 21, 2015 2:36 am **Posts:** 980

busterhax wrote:

ba114 wrote:

Yep the noise makes it annoying.
PLX recommend bridging a 0.1uF 50V capacitor as close to the dme as possible to help reduce unwanted noise. I found this in their WBO2 instructions. I'm going to try it on mine to see if it has a positive effect.

I'm guessing one end on the 0-5v side and one end on the ground side? I think I have one lying around that I could try out today or tomorrow.

Correct

ba114 · **Joined:** Wed Oct 21, 2015 2:36 am **Posts:** 980

busterhax wrote:

ba114 wrote:

Yep the noise makes it annoying.
PLX recommend bridging a 0.1uF 50V capacitor as close to the dme as possible to help reduce unwanted noise. I found this in their WBO2 instructions. I'm going to try it on mine to see if it has a positive effect.

I'm guessing one end on the 0-5v side and one end on the ground side? I think I have one lying around that I could try out today or tomorrow.

Have you got round to trying this yet? I haven't as my downpipe melted my beauty cover and coil harness due to excessive heat caused by too low timing advance (presumably).

Replacement parts are on the way.

busterhax · **Joined:** Wed Jan 22, 2014 6:54 pm **Posts:** 1773

ba114 wrote:

busterhax wrote:

ba114 wrote:

Yep the noise makes it annoying.
PLX recommend bridging a 0.1uF 50V capacitor as close to the dme as possible to help reduce unwanted noise. I found this in their WBO2 instructions. I'm going to try it on mine to see if it has a positive effect.

I'm guessing one end on the 0-5v side and one end on the ground side? I think I have one lying around that I could try out today or tomorrow.

Have you got round to trying this yet? I haven't as my downpipe melted my beauty cover and coil harness due to excessive heat caused by too low timing advance (presumably).

Replacement parts are on the way.

Not yet. I found some .47uf electrolytic caps lying around but didn't bother and ordered some .1uf ceramic caps which should hopefully be in this week. I'm against hacking the harness close to the DME so I'll likely just be adding it by the O2 plug. I'll post a before and after WOT log to compare.

ba114 · **Joined:** Wed Oct 21, 2015 2:36 am **Posts:** 980

busterhax wrote:

Not yet. I found some .47uf electrolytic caps lying around but didn't bother and ordered some .1uf ceramic caps which should hopefully be in this week. I'm against hacking the harness close to the DME so I'll likely just be adding it by the O2 plug. I'll post a before and after WOT log to compare.

Ok. It will be interesting to see. The purpose of doing it nearest the ECU is because the noise could be introduced in the wiring between the sensor(s) and the DME. By putting it at the DME you block the noise introduced in the wiring loops

busterhax · **Joined:** Wed Jan 22, 2014 6:54 pm **Posts:** 1773

ba114 wrote:

busterhax wrote:

Not yet. I found some .47uf electrolytic caps lying around but didn't bother and ordered some .1uf ceramic caps which should hopefully be in this week. I'm against hacking the harness close to the DME so I'll likely just be adding it by the O2 plug. I'll post a before and after WOT log to compare.

Ok. It will be interesting to see. The purpose of doing it nearest the ECU is because the noise could be introduced in the wiring between the sensor(s) and the DME. By putting it at the DME you block the noise introduced in the wiring loops

Yes I understand. I will likely find another solution before modifying my harness though. So I'll see if a cap by the map sensor is "good enough" or not

a32guy · **Joined:** Fri Mar 06, 2015 1:01 pm **Posts:** 36

busterhax wrote:

Yes I understand. I will likely find another solution before modifying my harness though. So I'll see if a cap by the map sensor is "good enough" or not

Please do keep us posted. My innovate SCG-1 arrives today and I will be attempting to wire it into the secondary front o2 sensor, for a faster sampling rate. I will certainly add a cap if it helps.

busterhax · **Joined:** Wed Jan 22, 2014 6:54 pm **Posts:** 1773

a32guy wrote:

busterhax wrote:

Yes I understand. I will likely find another solution before modifying my harness though. So I'll see if a cap by the map sensor is "good enough" or not

Please do keep us posted. My innovate SCG-1 arrives today and I will be attempting to wire it into the secondary front o2 sensor, for a faster sampling rate. I will certainly add a cap if it helps.

IIRC there is no logging of voltage from front o2s so you may have some trouble there.

ba114 · **Joined:** Wed Oct 21, 2015 2:36 am **Posts:** 980

a32guy wrote:

Please do keep us posted. My innovate SCG-1 arrives today and I will be attempting to wire it into the secondary front o2 sensor, for a faster sampling rate. I will certainly add a cap if it helps.

Its unclear to me whether this will work. My understanding is that if you hook something up to the o2, then the dme will attempt to use that data which may have undesirable effects

busterhax wrote:

Yes I understand. I will likely find another solution before modifying my harness though. So I'll see if a cap by the map sensor is "good enough" or not

i understand. My harness is already butchered near the DME anyway so i have no problems with a little more.

busterhax · **Joined:** Wed Jan 22, 2014 6:54 pm **Posts:** 1773

I'm getting some weird results. Is it the map sensor's signal wire and the ground that the cap should be connected to or the map sensor's power and ground?

ba114 · **Joined:** Wed Oct 21, 2015 2:36 am **Posts:** 980

busterhax wrote:

I'm getting some weird results. Is it the map sensor's signal wire and the ground that the cap should be connected to or the map sensor's power and ground?

According to the diagram on page 5, it should be between signal and ground.

https://www.plxdevices.com/v/vspfiles/support/user_guides/M-300TE_user_guide.pdf

RomRaider

Forum rules

Alternate Rear O2 wiring configuration

Who is online