fiatslug87 Posted July 2, 2019 Share Posted July 2, 2019 I think the new NTK O2 sensors are junk. The old ones had a ceramic body with three wires coming out into the three pin connector, the two new ones I purchased both have metal bodies and four wires coming out of the body into the three pin connector. I have the RenixEngineMonitor from Nickintime and both of the new ones pretty much stay at ~2volts when the truck is warmed up and the REM indicates a lean condition and open loop. I pulled an old one out of my other MJ that fluctuates between 0.2-4.8 volts and lean/rich in closed loop as it should, put it into the MJ that had the new sensor and now everything operates normally. I don't know when they changed, all the pictures I see still show a ceramic body. Anyone else have an issue with them? EDIT: This is in my '90 4.0L, "good" O2 sensor was from my '88 4.0L Link to comment Share on other sites More sharing options...
87MJTIM Posted July 2, 2019 Share Posted July 2, 2019 I am having issues with my O2 sensors as well. I had the NTK, also. After a few weeks/months, the REM show the O2 voltage holding steady at ~2.3 to 2.4. It wouldn't vary much above or below those amounts. The REM showed I was constantly in OPEN loop. I am on a second O2 sensor now - bosch?. The voltage does move up and down on a wider range, but it is still stuck in Open loop. Does anyone have one that is more reliable? Not C.R.A.P. Link to comment Share on other sites More sharing options...
fiatslug87 Posted July 2, 2019 Author Share Posted July 2, 2019 Do you remember if the NTK sensor had a metal or ceramic body and three or four wires coming out of the body? Link to comment Share on other sites More sharing options...
87MJTIM Posted July 2, 2019 Share Posted July 2, 2019 I don’t remember exactly. I think it was ceramic. I remember it was different the current one, which is metal. Link to comment Share on other sites More sharing options...
Ωhm Posted July 2, 2019 Share Posted July 2, 2019 Now I'm sure you guys have 'proved out' all that heater circuit stuff. Link to comment Share on other sites More sharing options...
87MJTIM Posted July 2, 2019 Share Posted July 2, 2019 The REM is registering 11.9-12 v from the heater relay. I do not recall testing the sensor end from the heater relay. Since the O2 sensor is getting power, I guess the heater relay is providing the power. (See 88 wiring diagram, 4.0L page 16.) What other test should I perform on the O2 system? Link to comment Share on other sites More sharing options...
Ωhm Posted July 2, 2019 Share Posted July 2, 2019 Disconnect O2S. Measure ohms across C229_A and C229_B at the component. Looking for ≈6ohms. On the connector harness side measure C229_B for a path to ground and check voltage at C229_A (voltage will follow the actions of the fuel pump relay) so with KEY ON, voltage will only show for 2-3 seconds. Retry if necessary. 23 minutes ago, 87MJTIM said: Since the O2 sensor is getting power, I guess the heater relay is providing the power. O2 sensor (Input side) receives power from the ECU, not the heater relay. Both heater and input share a common ground. Link to comment Share on other sites More sharing options...
fiatslug87 Posted July 2, 2019 Author Share Posted July 2, 2019 52 minutes ago, Ωhm said: Now I'm sure you guys have 'proved out' all that heater circuit stuff. In my case when I replaced the sensor with a known "good" one from another MJ everything was back to normal. Also when I checked resistance of the bad ones between A&B I got 4.4 ohms, it should be 5-7. Link to comment Share on other sites More sharing options...
87MJTIM Posted July 2, 2019 Share Posted July 2, 2019 I'll try those tests later the is week. Link to comment Share on other sites More sharing options...
Ωhm Posted July 2, 2019 Share Posted July 2, 2019 2 minutes ago, fiatslug87 said: with a known "good" one That proved it out. Link to comment Share on other sites More sharing options...
fiatslug87 Posted July 2, 2019 Author Share Posted July 2, 2019 4 minutes ago, Ωhm said: That proved it out. Yeah, It's nice having three MJs, at least one is in good operating condition at any one time so that cross-over tests can be performed. Link to comment Share on other sites More sharing options...
Ωhm Posted July 2, 2019 Share Posted July 2, 2019 2 minutes ago, 87MJTIM said: I'll try those tests later the is week. One thing I'm having problems with (88 Elect Manual pg16) is O2 Heater Relay pins 1(30) and 5(86). Check color code, maybe swapped when compared to Elect Manual. Link to comment Share on other sites More sharing options...
Jeep Driver Posted July 2, 2019 Share Posted July 2, 2019 Link to comment Share on other sites More sharing options...
Jeep Driver Posted July 2, 2019 Share Posted July 2, 2019 https://www.ebay.com/p/Oxygen-Sensor-Direct-Fit-NGK-23553/76143591?iid=163684314905&rt=nc Link to comment Share on other sites More sharing options...
87MJTIM Posted July 2, 2019 Share Posted July 2, 2019 I am reading the Renix Fuel Injection Manual for O2 sensors, pp 41-43. The last paragraph on p. 41 reads: The oxygen sensor heater relay is controlled by the ECU. When the ECU determines high exhaust gas tares and exhaust gas oxygen sensor heating is no longer required, the ECU completes the relay coil ground circuit. When the ground circuit is completed, the relay contacts open, and the exhaust gas oxygen sensor is disabled. Does that mean the relay is Normally Closed? If so, would swapping relays around mess up the operation of the heater relay and O2 sensors? Link to comment Share on other sites More sharing options...
87MJTIM Posted July 2, 2019 Share Posted July 2, 2019 15 minutes ago, Jeep Driver said: https://www.ebay.com/p/Oxygen-Sensor-Direct-Fit-NGK-23553/76143591?iid=163684314905&rt=nc I found the same part on Jeff Bezos's site, but is shows metal not ceramic. Link to comment Share on other sites More sharing options...
Jeep Driver Posted July 2, 2019 Share Posted July 2, 2019 1 minute ago, 87MJTIM said: I found the same part on Jeff Bezos's site, but is shows metal not ceramic. My intuition tells me........... And we've seen this with other parts such as fuel pumps. Manufactures are no longer making MJ/XJ specific parts for Renix era and I suspect soon 90s era models. I beat the drum............... Better set yourselves up NOW if you want to drive your MJ for the next 5 years or so...........after that, WTFKs? Link to comment Share on other sites More sharing options...
Ωhm Posted July 2, 2019 Share Posted July 2, 2019 11 minutes ago, 87MJTIM said: Does that mean the relay is Normally Closed? Yes When relay coil is OFF (de-energized), relay pins 1(30) and 3(87a) make contact. These are the pins used for O2 Heater circuit. 21 minutes ago, 87MJTIM said: If so, would swapping relays around mess up the operation of the heater relay and O2 sensors? No These types of relays are all structured and function the same. Link to comment Share on other sites More sharing options...
87MJTIM Posted July 2, 2019 Share Posted July 2, 2019 I thought most relays were NO, unless marked NC. Or is the wiring setup to account for NC condition? Link to comment Share on other sites More sharing options...
Ωhm Posted July 2, 2019 Share Posted July 2, 2019 O2 heater relay doesn't turn O2 heater circuit ON (de-energized), it turns it OFF (energized). Link to comment Share on other sites More sharing options...
Ωhm Posted July 2, 2019 Share Posted July 2, 2019 During a WOT condition, exhaust manifold is acting like a giant blow torch. More fuel. No need for the O2 heater circuit, only more fuel. Now is when the O2 heater relay is energized (heater circuit OFF) and B+ is supplied to the normally open (NO) contact. This contact bypasses the fuel pump ballast resistor applying B+ directly to the fuel pump, where its needed most. Link to comment Share on other sites More sharing options...
87MJTIM Posted July 2, 2019 Share Posted July 2, 2019 3 hours ago, Ωhm said: Disconnect O2S. Measure ohms across C229_A and C229_B at the component. Looking for ≈6ohms. On the connector harness side measure C229_B for a path to ground and check voltage at C229_A (voltage will follow the actions of the fuel pump relay) so with KEY ON, voltage will only show for 2-3 seconds. Retry if necessary. O2 sensor (Input side) receives power from the ECU, not the heater relay. Both heater and input share a common ground. Just did these three tests C229 A-B: 5.7 ohms C229 B to ground: good, all zeros, not OL C229A KOEO 11.8v, (Battery shows 12.5v) Link to comment Share on other sites More sharing options...
Ωhm Posted July 2, 2019 Share Posted July 2, 2019 That 'proved out' its not your heater circuit giving you your problem. Link to comment Share on other sites More sharing options...
87MJTIM Posted July 2, 2019 Share Posted July 2, 2019 BTW I have a '90 ECU I have not performed the C101 elimination (yet) The REM shows the O2 sensor moving up and down, but it will stay at or near one reading for long time spans: 2.0 or less and never (or very seldom) higher. It stays in open loop most of the time. When it does switch to closed loop, the O2 sensor will swing from high to low. Also, fuel trims will drop below 128. (I guess that is good, since the ECU is trying to cut back on fuel consumption. Increased gas mileage.) Link to comment Share on other sites More sharing options...
Ωhm Posted July 2, 2019 Share Posted July 2, 2019 8 minutes ago, 87MJTIM said: C229A KOEO 11.8v, (Battery shows 12.5v) Question. Was this voltage reading steady, or did it follow the actions of the fuel pump relay (ON for 2-3 seconds)? Link to comment Share on other sites More sharing options...
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