hakukamana Posted March 6, 2019 Share Posted March 6, 2019 OK, as the title indicates, I have been experiencing multiple O2 failures. I have checked power, signal voltage, ground resistance. Checked relay power, I had a bad O2 sensor would not go into closed loop and defaulted to open loop, lean mixture. This is the default mode for the ECU. Purchased a new NTK O2 sensor, installed it, perfect, works just like it is supposed to work, everything is working correctly, "WRONG", 4 days. Hooked the scanner up looking at live data, initially moving from open to closed loop at start up, but no switching from lean to rich, at operating temp, finally just sits there at open loop, lean again. OK, so now I buy a new Bosch O2 sensor, again everything is as it should be at start up, open loop switching from lean to rich goes into closed loop, mixture switching continues to occur, voltages are working in range, pulse widths are correct, short term fuel trims are adjusting. 3 days later its dead again. Scanner is a MT 2500 so I am reading live data. The only thing I can think of is the sensors are being contaminated by the combustion process and fouling or shorting out the sensors. Anyone have any thoughts????? Link to comment Share on other sites More sharing options...
Fernando87mj Posted March 6, 2019 Share Posted March 6, 2019 Have you checked the o2 sensor heater circuit ? iirc it Should be the orange wire going to your o2 sensor connector on the harness side. You should be getting 12-13 volts. Check what you’re getting with a multimeter. I had that same problem and I realized that I was only getting 8volts. Here’s the thread on this issue edit: missed the part where you said , you checked relay power already . Will stay tuned as curious to what it might be Link to comment Share on other sites More sharing options...
hakukamana Posted March 6, 2019 Author Share Posted March 6, 2019 Key on engine off, heater voltage circuit is reading 11.88 volts. Ground for the DMM was connected to the sensor ground circuit at the dipstick block bolt. Gounding point is clean and shiny. Ohms for the heater circuit on the O2 sensor were reading 19.2 between A & B which is not in the spec range. The FSM indicates 5 to 7 ohms if not replace the sensor. which I have done now twice. The new sensors work correctly when initially installed, but over the course of a few days, they seem to be failing, that is the question?? Link to comment Share on other sites More sharing options...
Ωhm Posted March 6, 2019 Share Posted March 6, 2019 14 minutes ago, hakukamana said: Ohms for the heater circuit on the O2 sensor were reading 19.2 between A & B which is not in the spec range. Not trying to be a smartazz here, but have you check the battery in your DMM? 16 minutes ago, hakukamana said: The new sensors work correctly when initially installed, but over the course of a few days, they seem to be failing, that is the question?? Did you note the STFT and LTFT numbers when installing new O2? Link to comment Share on other sites More sharing options...
hakukamana Posted March 6, 2019 Author Share Posted March 6, 2019 DMM battery is good Fluke 88. Put in a new 9V just for kicks. Battery voltage is 12.48 at the terminals. KOEO battery power to the O2 harness treminal A, 11.88V again ground to the sensor circuit ground point, at the dipstick. Initial O2 readings with new O2 STFT and LTFT were moving and adjusting, after the failure LTFT fixed, STFT can't remember. I just got another brand new Bosch O2, ready to install. Will give you an update when I scan. Link to comment Share on other sites More sharing options...
Eagle Posted March 6, 2019 Share Posted March 6, 2019 3 hours ago, hakukamana said: OK, as the title indicates, I have been experiencing multiple O2 failures. I have checked power, signal voltage, ground resistance. Checked relay power, I had a bad O2 sensor would not go into closed loop and defaulted to open loop, lean mixture. This is the default mode for the ECU. ... Anyone have any thoughts????? Default mode for the Renix ECU in open loop mode is rich, not lean. Link to comment Share on other sites More sharing options...
hakukamana Posted March 6, 2019 Author Share Posted March 6, 2019 My failure was open/lean. You are correct Eagle FSM default is open/rich. Installed a new Bosch O2, works just like its supposed to, enclosed are two video's start up, and operating temp. We will see how long this one lasts? Start_Up.mp4 Link to comment Share on other sites More sharing options...
hakukamana Posted March 6, 2019 Author Share Posted March 6, 2019 It appears that I can't upload the operating temps video Link to comment Share on other sites More sharing options...
Ωhm Posted March 6, 2019 Share Posted March 6, 2019 Your recording show engine is running RICH. It's in CLSD loop, STFT is taking fuel away (noted by low INJ PW). Link to comment Share on other sites More sharing options...
hakukamana Posted March 7, 2019 Author Share Posted March 7, 2019 Ohm it's moving from Rich to Lean on the scanner, that was cold start scan. It was in closed loop. The pulse width was high, at cold start, then at operating temperature drops down to the 5.? Range. Short term ft was in the 70s, long term was fixed at 128 Link to comment Share on other sites More sharing options...
Ωhm Posted March 7, 2019 Share Posted March 7, 2019 You're correct, I was using (O2) V as INJ PW. Can't see INJ PW on screen. Link to comment Share on other sites More sharing options...
hakukamana Posted March 7, 2019 Author Share Posted March 7, 2019 The operating temp scan has the O2 voltages down below 1 and then moving up as high as the 4 +while thats going on its switching from rich to lean, pulse width is in the 5's the new O2 is working as it should but so did the NTK that I put in a week ago. Then something happened? It froze in open loop/lean and voltages were stuck in the 3V range. Even when it warmed up nothing changed. Its a weird issue, new runs and operates fine, a couple of days of driving and not more than 80 miles, bang its DOA. Stick a new one in works like a champ, drive a few days and again its dust. I don't think the sensors are dying on their own, I am just wondering if its something in the O2 circuit or the ECU reference signals. Link to comment Share on other sites More sharing options...
hakukamana Posted March 7, 2019 Author Share Posted March 7, 2019 This is at 195 * operating temp 195_Operating_temp.mp4 Link to comment Share on other sites More sharing options...
hakukamana Posted March 7, 2019 Author Share Posted March 7, 2019 Its really hard to get a video squeezed into 9.77MB's Link to comment Share on other sites More sharing options...
Ωhm Posted March 7, 2019 Share Posted March 7, 2019 That last recording look normal and seems well within its range of authority. MT2500 only reads and displays live data, so O2S circuits should be good. Hope this new O2S solves the problem. Link to comment Share on other sites More sharing options...
hakukamana Posted March 7, 2019 Author Share Posted March 7, 2019 This is number (3), for O2 sensors in less than 10 days Link to comment Share on other sites More sharing options...
Ωhm Posted March 7, 2019 Share Posted March 7, 2019 Maybe number 3 is your lucky number. Keep us posted. Link to comment Share on other sites More sharing options...
Ωhm Posted March 7, 2019 Share Posted March 7, 2019 Could it possibly take 3-4 days to trip LTFT? Keep an eye on it. Link to comment Share on other sites More sharing options...
hakukamana Posted March 7, 2019 Author Share Posted March 7, 2019 Are you saying it could take 3-4 days to trip the LTFT? What triggers the LTFT to change? Driving conditions? Link to comment Share on other sites More sharing options...
Ωhm Posted March 7, 2019 Share Posted March 7, 2019 I'm not saying that, I'm wondering if it will. LTFT should trigger when STFT reaches one of its two limits (0 or 255). LTFT will then move lower or higher, allowing STFT (128) to start all over again. Thats the intent of STFT and LTFT. Now what I don't know is if RENIX will do this. Link to comment Share on other sites More sharing options...
hakukamana Posted March 7, 2019 Author Share Posted March 7, 2019 Interesting so what drives the STFT, so that it would reach a limit boundry? Is it normal for STFT to stay within the 0 to 255 limits. I think LTFT is at 128 based on the last operating temperature scan. If the STFT reaches the 0/255 limits what happens to LTFT? Link to comment Share on other sites More sharing options...
Ωhm Posted March 7, 2019 Share Posted March 7, 2019 STFT is O2S switching based. More lean or more rich move the STFT numbers which will adds or remove fuel through INJ PW times. When STFT reaches either one of its two limits, LTFT should move in the same direction, adding or subtracting a few number, resetting STFT (128) and starting the whole process over again. Link to comment Share on other sites More sharing options...
Jeep Driver Posted March 7, 2019 Share Posted March 7, 2019 Where are you getting your temp readings from? Link to comment Share on other sites More sharing options...
hakukamana Posted March 7, 2019 Author Share Posted March 7, 2019 Coolant temp switch on the block, operating temperature readings are correct, from cold start up to full operating temperature. I can monitor the temperature as the truck heats up after the thermostat opens runs about 187 at idle. Link to comment Share on other sites More sharing options...
hakukamana Posted March 7, 2019 Author Share Posted March 7, 2019 I run a 195 thermostat Link to comment Share on other sites More sharing options...
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