RomRaider

Care to elaborate?

This needs to be explored in a bit more detail but my understanding of the code is the byte at x22C is the value by which the 'error counter' is incremented if the ECU detects a problem with this particular function. Default value is 02 and if it is incremented enough times till the value at x254 (0A) is exceeded, a DTC is thrown. By setting x22C to '00' we are preventing this counter from incrementing towards the threshold value of 0A. You are suggesting we set this value to same as the threshold needed to throw this DTC so it will increment to the threshold after just one occurrence instead of several occurrences.

I guess the subroutine for this DTC needs to be looked at. sub_PROG_27D20. Alec, do you want to explore this in a bit more detail?



edit:
Added BA's diagram

Unfortunately my assembly skills aren't up to par yet. Just from toying around the old fashioned way, i've found that the "array of 0A" values pretty much mimics the "02 array". As you know, leaving post cat o2s electrically connected, but in open air, the ecu will still flag a DTC even with x22C set to 00. However, when x254 is set to 00, the DTC(s) will not flag even with the o2 sensors plugged in.

Ba114 was having this issue with his MAP sensor connected to the post cat o2 connector(for logging boost) and setting x254 to 00 fixed this for him.

Apologies for derailing the thread a bit.

Which DTC exactly? It is my understanding that by setting x22C to 00h, the DTC for "Rear O2 Sensor HEATER" will never be set. A different DTC for voltage or efficiency may be set if sensor is electrically connected.

Anyway, looks like we need to explore this a bit more. So good discussion everyone.

I was getting dtc 61.
My setup is:
1 channel o2. wbo2 in bank 1 rear o2, map sensor in bank 2 rear o2

Can you post up how you wired the WBO2 and MAP sensors into the Rear O2 wiring harness?

I wouldn't have thought the Heater current sensing would be affected once DTC 79,61 was disabled. What if you swap the banks? Does the DTC change from 61 to 79? Or does DTC 61 remain?

We should probably move this discussion into a new thread labeled "Alternate Rear O2 wiring configuration" or something like that.

The map sensor is grabbing the 5v from the tps. Signal + is self explanatory and the signal - and heater ground were bridged I think from memory. Will double check once I can get access to the wiring again.

No so easy to switch banks due to the 12v and 5v wiring plugs I made but in the interests of development I'll give it a go next weekend.

We are talking about the 8 wires that go to the rear O2 sensors. Please explain how these are used. If you are using wirng in addition to that (for example, TPS wiring) you shoul've mentioned that in the first place...


Anyway, to put all s*** and language discrepancies aside, please draw a wiring schematic that explains all of your modifications.

I don't know why you feel the need to be attacking me in both this thread and the closed loop thread.

But fwiw, per your question in the other thread, I am a 100% English speaking Australian, of Caucasian descent (if that matters).

Something is clearly pissing you off today so I will provide more information and maybe you will refrain from the need to speak in such a condescending and derogatory manner. It was mentioned a MAP sensor was being used, i (we) perhaps assumed that you knew that MAP sensors run off a 5v feed rather than the standard 12v hence requiring a different voltage feed.

I [*]should[*] have specified that i am also using a harness from a EURO (australian) M52 which did not even have rear O2s pinned at the ECU connector so i had to add them in using the ETM as a guide, however this fact is also irrelevant.

Buster provided a solution which I am most grateful for and I've offered to help troubleshoot why it is occurring from a hardware perspective as it seems I'm the only one with this configuration currently, but I'm sure a lot of people will benefit from figuring this out.


[diagram redacted. see updated diagram in first post]

You're right. My apologies for going off.

In your wiring schematic, is it necessary to have pins 61 and 79 bridged to ground? I thought only the voltages coming off the sensors would have needed to be integrated.

When i was wiring the MAP sensor, the only way i was able to get it to register voltages was to bridge the two grounds.

I had assumed that simply running the 5v to the sensor, the signal to the ecu and grounding the MAP ground would be sufficient (my basic electronics knowledge thought this) but for some reason this was not working.

However now having re-read how the DME handles the O2 sensor grounds, i think i can confirm why it was throwing the DTC. It appears the heating grounds aren't actually a fixed ground, but rather a PWM ground output and will flag a DTC if connected to ground directly, which occurs through bridging to signal - (pin 70).

I'll re-wire the ground this weekend, removing the heating ground from the wiring and confirm whether
a) i still get my MAP sensor readings, and
b) No DTCs are thrown.

Now that my WBO2 is wired in (the same as the MAP) it's likely that i would also be throwing the DTC if x254 wasn't 00'd so i'll have to fix the wiring on that too.

About using MAP sensor i'm experimenting something on my supercharger project, using it in place of the MAF sensor. Using voltage regulator to lower 12v(14v car running) and have 5v on MAP sensor and then wiring map output to MAF output to the ECU. Will test it in a few days..

This thread is specifically about using the rear o2 inputs for alternate sensors.

I would suggest logging your map through the rear o2s at the same time as logging maf voltage so you can work on your conversion.

There was a thread on here somewhere by tkelly where they had started on a map conversion. Maybe it will provide you with some inspiration.

Yeah, I also would've thought a simple 5V input + chassis/ECU ground + signal voltage going to one of the rear O2 sensor voltage pins would've been enough for the MAP sensor.

Still, it is interesting what your empirical findings show. I really think we need to thoroughly examine exactly what happens in the DTC subroutines and how those two calibration bytes play into effect. My original hypotheses of the the value we set to 00h as being the 'counter' may not entirely be correct. And if setting it to the same value (0Ah) as the 'comparator' value being 'enough' to take care of this problem, is intriguing.

And yes, it is an important fact to note that this ECU (probably most) PWM the ground part of the circuit. This seems to be a norm in most electronic industries.

Just to close this out, the issue can be corrected through wiring.

I disconnected the O2 heater ground from my wiring on both the wideband in bank 1 rear o2 and the map sensor on bank 2 rear o2 and can confirm that no DTCs are thrown.

So as per previous post, the heating ground being permanently grounded was causing the DTC as this is actually a PWM ground output from the DME.

So how exactly is it set up? 5v from tps, map output to the o2 signal wire, then chassis ground the non-heating ground?