O2 sensor problem

[Jeep Driver]

Glad you figured it out, I had a sneaking suspicion the new ECU was giving you issues. I just figure I'd add a little knowledge in for later diagnostic of future users that may browse the forums.

 

For more indepth diagnosis of the closed loop process, keep an eye on the short term fuel trim reading. This is the adaptive offset from the base fuel curve and is directly affected by the o2 sensor when In closed loop. 128 is base, lower reading mean less fuel then base and higher readings mean adding more fuel then base. When the o2 is non-responsive you can watch the short term reading either drop to 0 or rise to 255. If it sits there for more then a second then the ECU will give up and go back to open loop. It's all laid out on the diagnostic screen at the very bottom so take a look sometime.

 

As for the Renix Engine Monitor, besides the heater relay which is a direct reading, it reads all its info directly from the ECU stream so long as it is reading in data properly then what you see is exactly what the ECU sees. This can be useful for checking bad connections as a sensor may be working but the ECU is not able to read it.

 

The update speed is also a good point to raise and one that has made be very glad that I can call all the shots with this device. The ECU sends about 40 frames of data a second and if I were to display them instantly then the screen would be basically unreadable as the LCDs response time can't keep up. I have added a few different speeds, ludicrous being the upper limit of what is still readable with the screen. This is fast enough to easily watch the o2 sensor swing between high and low and it's actually really fun to watch. Here's an older video to see what that looks like: https://www.instagram.com/p/BJhNDNKhEBs/

 

Anyway sorry for the info dump but hope that sheds some insight on everything!

When are you going to develop one for the Renix 2.5?

[NickInTimeFilms]

Whenever I have some free time and can figure out the circuitry needed. If it worked the same way as the 4.0L then it would have been done a long time ago. It's proven very difficult to crack at it works differently then any other comunication system I've seen so far. It appears there are 2 data lines but none of them are clocks so I can't figure out the high and low requirements yet. I'm hoping one day I get it

[big66440]

Thanks for the info Nick, this monitor is some of the best money I've spent on my renix so far. Do you have any pointers on getting it to read transmission data? I checked voltage to pin 15 at the diagnostic connector ( key on engine off ) and it shows 5 volts.

[NickInTimeFilms]

Thanks for the info Nick, this monitor is some of the best money I've spent on my renix so far. Do you have any pointers on getting it to read transmission data? I checked voltage to pin 15 at the diagnostic connector ( key on engine off ) and it shows 5 volts.

Well, let's just run through it all real quick. Simplest thing first, and this one has gotten a few users, make sure the REM is set to Automatic Transmission under Options > Vehicle. If this is set to Manual then the TCU search code is skipped and that's for any screen.

 

Next, the TCU uses pin D2-15 for TX and pin D2-7 for ground return.

 

With key on, engine off I get 0.5v with Pos lead to D2-15 and Neg to D2-7 or 10.5v with Pos lead to D2-15 and Neg to D2-4 which is ignition positive.

If your multimeter has a continuity tester with built in beeper then measure with Pos lead to D2-15 and Neg to D2-4 and you should hear a chirping repeating pattern sort of like really fast morse code.

If all that checks out then the diagnostic port and TCU should be ok and outputting data.

 

Now we will check the REM side. With the unit plugged into a usb cable, check the voltage on the adapter. With Pos to D2-15 and Neg to D2-7 you should see about 4.3V. If that's the case then the pull up resistor is working and the ethernet connection is good.

 

If all that checks out then i'm not too sure what to tell you, still has a factory TCU from the same era that works? Maybe you have a special case or the timing is different but regardless it should show something. Let me know what you get.

[Airsuperiority]

On 4/6/2017 at 8:01 PM, big66440 said:

SOLVED!!!! The ECM i got from ebay must have burned out my O2 sensors!!! I got a new NTK oxygen sensor and installed my old ECM and it did the trick!!. I must have not measured voltage correctly at the sensor, either way I'm glad it's over.

I just had the same issue with the 428 Ecm swap. Can’t get a closed loop and the O2 sensor was only 3k miles old. Did the new sensor do the trick? How long has it lasted with the new Ecm?

[big66440]

On 5/14/2023 at 1:02 PM, Airsuperiority said:

I just had the same issue with the 428 Ecm swap. Can’t get a closed loop and the O2 sensor was only 3k miles old. Did the new sensor do the trick? How long has it lasted with the new Ecm?

The new sensor is still going strong, it turns out the ECM I had bought on eBay was causing the O2 sensor to fail.

[Airsuperiority]

Ah I see. Did you change ECMs then? I think I’m going to put the 429 in instead. 

[big66440]

On 5/16/2023 at 10:30 AM, Airsuperiority said:

Ah I see. Did you change ECMs then? I think I’m going to put the 429 in instead. 

Yes I threw away the ECM causing the issues with the O2 sensors and installed the ECM that was originally in my truck as well as a new O2 sensor.