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Renix Wideband O2 Control Using the R.E.M.


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There doesn't seem to be any good replacement Renix o2 sensors available anymore unless you get lucky and find a NOS Mopar sensor on Ebay. My less than a year old NTK sensor has never really performed well, (LTFTs were usually in the 140s, not too high but still using more fuel than needed) and recently it started failing closed loop repeatedly and only swung from 2-2.5 Volts. Luckily, Nick already did the hard work with his Renix Engine Monitor, and it's possible to use a wideband AFR gauge to send a signal to the REM where some math gets done and it replicates a narrow band signal to send to the ECU. Shoutout to him answering my emails on a Saturday night after I didn't fully understand his web page and the RPMs shot up to 2500 on startup. He got me squared away, so I'm writing this to help anyone else who wants to do this.

 

Here is my data stream before and after setting this up. After resetting the ECU and driving it around today, it's running better than it ever has, and LTFT is at 126.

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I used the same AEM gauge that Nick did, AVM-30-0300. It has a 0-5V analog output on it which is perfect for sending to the REM. 

Wiring it is pretty straight forward, you must ground both the black and brown wires on the gauge, the brown is the ground for the 0-5V output. I used the grommet in the corner next to the brake master, I think this is used for the clutch master in a manual vehicle. My O2 bung is further downstream than stock with the Pacesetter headers, so I went over the engine with the wideband harness [yellow]. The white wire on the AEM goes to pin 2 of the REM adapter, and a wire [red] will be run from pin 4 and down along the harness to the stock O2 connector. Cut the end off of an old sensor and attach this wire to the gray wire on that connector. Ground the black and brown wires in the cab, and attach the red wire in the cab to keyed power. I used an add a fuse on the radio fuse.

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^ Fill the grommet with RTV when everything is done

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You must remove the solder bridge on the adapter. Not doing so will send the o2 heater relay voltage to the sensor wire and it will rev to 2500RPM on startup. 

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REM Setup

Nick's site is a little confusing here since the numbers on the switch are upside down. Leave pin 2 up, and switch pin 4 down. My pin 1 is down to control the e-fan. 

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Go to Options>More>Settings>Wideband and select Pin 2 on Wideband Pin to tell the REM were the signal is coming from. Select the output range for your gauge, the AEM is 8.5: to 18:1 for 0-5V. 

Key on with the wire removed from port 4, select AFR on the REM gauge screen and ensure that you see the same number on both gauges. It may take a few seconds for this to match since the computer shows a scaled TPS voltage as o2 voltage at first when the key is turned. If the numbers match, start the engine and run the wideband sync test in the Test menu.

If you pass that, then re connect pin 4 to send the AFR signal to the ECU. Switch Wideband Tune to Y. If everything is done correctly, it will enter closed loop and begin to use the new signal.

 

This opens the door to minor AFR tuning by adjusting the target ratio (at the bottom of Pages), but too much will just cause closed loop to fail. There is also a closed loop helper mode to help keep it closed if it pops out sometimes.

 

Mount the gauge wherever you like. I printed a pod that I taped to the column with double sided foam tape.

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  • 1 month later...

Update after a month of driving: It's been working great, LTFTs cycling between 126-132. MPG went from 10-11 with the bad sensor to 16-17, which is about 1mpg higher than what I was getting before the sensor went bad, but that was also on 3.55s and 31s, when I now have 4.56 and 32s.

 

I have found that you need to give the wideband a few moments to heat up before starting the engine, kind of like waiting for the glow plugs in a diesel. If you don't, the computer will most likely try closed loop before the sensor is ready, and it will loop fault lean. It's more apparent on a warm engine since it will take less time after start to go into closed loop.

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  • keeponjeepinon changed the title to Renix Wideband O2 Control Using the R.E.M.
  • 4 weeks later...

I completed the same mod and have experienced similar results.

 

I used an AEM inline controller (P/N 30-0310) and used the existing 02 heater and ground circuits on the harness to power the controller and ground the sensor, respectively. Reduced overall wiring and seemed neater.

 

The controller cycles power when a WOT condition triggers the heater relay, but I’ve found it to reliably start swinging again before the ECU reverts to closed loop.

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Great Write-up! If you don't mind, I'll link this thread on my site to help folks out in the future. 

Would also like to report that as of Renduinix V9.16 there is a bug with the AEM Wideband profile that was preventing the REM from correctly detecting when the sensor was in "Heat" mode. The REM should output a lean signal if it detects Heat mode so that when the ECU tries to correct, it adds fuel instead of pulls fuel to keep a stable idle, but with the bug it was only defaulting rich.

Never caught it since my Jeep hasn't driven since V9.15! :shaking:

This issue should be fixed in V9.31 now so thanks for the heads up!

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On 7/11/2022 at 8:35 PM, NickInTimeFilms said:

Great Write-up! If you don't mind, I'll link this thread on my site to help folks out in the future. 

Sure, go ahead. I just finished moving across the country with it, so it definitely works. It was cool watching the LTFTs go from 130 in Ohio, to 100 at 7k feet in Flagstaff, then back to 128 at sea level in San Diego 

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