I find it very hard to believe that these O2's are that sensitive on a off road truck.

 

Damage to what wiring? I've tested all of the wires between the connector (where the o2 sensor plugs into) and the ECM, and all 4 wires for each sensor checked out for continuity (1 wire is for power, the other 3 for readings).

When I hook up new sensors, I can watch the live data and them function properly and adapt within spec when revved, etc. The truck fuels properly and get proper gas mileage. Shortly after installing (day or two I'm guessing) I get codes 0134 & 0154 (bank 1 sens 1 no activity, bank 2 sens 1 no activity) and I can watch the live data and it does not move or adjust, just sits at the default reading and leaves the truck in OPEN LOOP (hence the overfueling and beyond poor gas mileage) and this is what I am calling a DEAD o2 sensor.

Am I right in assuming the heating element within the sensor tells the ECU when the truck is warmed up and then goes in closed loop? Well, within days of installing new sensors and watching them function properly it goes back to "no activity" (P0134, P0154) and sensors not working or giving readings, the truck stays in open loop.

So i'm trying to find out what is killing these o2 sensors or causing this no activity reading and keeping the truck in open loop.

 

And to add to this part, I watched the sensor heat up to normal operating temperature, the fuel mixture lean out to spec, and the truck go into closed loop as it should. I watched it do it twice to make sure the truck was running properly and that the sensors were indeed working.
Unless I'm not understanding how this works, I don't believe the ECU controls the heating element within the o2 sensor...unless you are talking about a different heater?

 

Well...........my "bad sensor" heating element has continuity and measures 3.2 ohms......

Burning out the heating element does not seam to be at my root cause.

 

Thanks for doing this, I should check mine too. I have one set off the truck from going no activity, and the current set on that I can check.

Question, i'm still learning the multimeter, exactly how did you get your reading? Set to Ohms, but where did you put red & black and do I need the sensor plugged and hooked up? Need the car on and running?

Thanks.

 

On a completely different brand of vehicle, it was "common knowledge" that oil got into the threads of the sensor and ruined the sensor, resulting in failure of the sensor's heating element. In troubleshooting my own problems along those lines, I applied the copper sealant commonly used in exhaust joints and header replacement to "seal" around the O2 sensor after a fresh install. I could smell it cooking off and then observed the O2 sensor failing as it had before. As a test, I sprayed PB Blaster all over the O2 sensor thinking that if oil could get past the copper sealant, PB Blaster sure as hell would and would be pretty easy to see on the O2 sensor. After I let it sit for a while, I cleaned off the PB Blaster and copper sealant, removed the O2 sensor and there was no PB Blaster on the sensor, much less oil. I felt like that was a pretty good indication that the oil theory wasn't correct.

Next, I looked at the ECU as I was pretty sure that the heating element was being left on after it had already heated up. The duty cycle on those heating elements isn't very long... most exhausts get up to temp pretty quickly so, if the heating element is staying on pretty much constantly it will "burn out" quickly. The first thing I did was wire a switch to my O2 sensor's heating element wire. I manually turned off the heater after about five minutes of driving. GREAT SUCCESS!!! The O2 sensor lasted weeks. The vehicle in question used T5 engine management and I used some available software to tell the ECU to quit turning on the heating element. Again, the O2 sensor lasted for ages. I finally had someone more knowledgeable than I reflash the ECU with the standard ROM and never had another problem with the O2 sensors burning out early.

Moral of the story: I'd take a hard look at the ECU. I haven't had time to dig into the engine management software in our ECUs but I imagine someone has and can tell you whether the ECU can be "tuned" to turn off the heating element. I know it's different vehicles and different engine management software, but it may be worth a shot.

 

I just ran into similar codes last night (O2 no activity, rich running). (was 5 codes - 2 for no activity, cylinder 7 misfire, and a few other misfire codes)

Turns out it was a stuck injector. Giveaway was that the fuel pressure was staying very low after cranking the engine. (pushing on the schraeder valve only released a tiny bit of pressure).

I pulled the plenum, and pulled the injectors from the intake - turned on the fuel pump, and you could see the fuel coming out of injector 7.

Replaced injector, then made a really stupid mistake - I didn't pull the plug, and turned the engine over - I think the cylinder was full of gas, and hydrolocked the engine. Starter is now making an ugly noise, and not engaging - hoping it's only a buggered starter.......

 

OK, so its not the heating element, and you've checked for mechanical damage. You are actually blowing the sensors. There are two ways to do that: the ECU can damage them (difficult to test unless you have a spare ECU lying around) or your exhaust can be doing it.

Let's talk about that. What do these failed sensors look like? Are they caked with black soot? Is the soot or anything on them oily? If it is sooty, have you tried to clean the sensor and reinstall it? It might simply be plugged from the soot. This would lead you toward a root cause of engine running/fuel issues.

 

Hmm...I assumed the sensors would appear black and "sooty" just from normal exhaust. I have two sets of sooty sensors, I will try cleaning them, reinstalling, and gonna have to get my hands on a live data reader. Not sure why I worked on cleaning the connectors so well and NOT even thinking about the sensor itself.

So what you're saying is, these sensors are sensitive to overfueling? Which would lead me to look for something else causing the truck to overfuel? What else should I be checking? Plugs? Injectors? I'm still a noob mechanically but I can figure it out with a little help.

Thanks.

 

They will be sooty normally, but there is sooty and then there's caked up sooty. The later is bad. Heated O2 sensors are supposedly less susceptible to this because they can burn that stuff off better. I don't really know for sure.

First things first. I know you tested the heater on one or more of these sensors. If you check the ohm reading across any terminals other than the heater, just thrown the sensor in the trash. That's right....the little current coming from a standard volt/ohm meter is enough to kill a sensor. So don't do that.

There are two ways to test a sensor, but either way requires a high impedance volt meter. Pretty much any quality digital voltmeter can handle this. In either situation, you hook up the positive to the signal wire of the O2 sensor (make sure you are in DC voltage mode, not ohms/resistance or you will kill the sensor), and find a good ground on the truck for the other side, or simply ground it to the body of the sensor if its out of the truck. If it's in the truck, get it warmed up. Once it is, you should see voltages going around .45 volts. If it goes down to .2 and up to .7, it's working. When you hit the gas, it should go down quickly. If you're doing this on the truck, it will tell you whether the ECU is bad, because you can compare it with your OBDII live data.

Bonus points if you can scrounge up an oscilloscope for this. Set it on a 1 volt range and go for it. You should see a nice sine wave at idle.

If it's off the truck, stick a propane torch on it (hit the perforated section with the blue part of the flame). You should see .5 or .6 volts within 20 seconds. Take the flame off. It should be back down to .1 within 4 seconds. If not, it's bad. My understanding is that if the voltage doesn't fall quickly on this test, its likely silicone fouling.

What kills them besides soot? Lead (an unlikely issue) and silicone (any silicone sealer used in/around the crank case that isn't specifically O2 sensor safe can and absolutely will cause problems like this) are the big ones. How is this thing running in open loop mode (other than rich)? If its running poorly, you probably have something easy to go after. Sure, plugs and wires or even a bad coil will make it do that, but you'd likely see performance issues if that's the case.

All of this is pretty general information. None of it Rover specific. If you can narrow it down to some performance issue, I'm sure someone here can assist more than I with the likely culprits. I haven't had to deal with too much of and sort of fueling issues on my Rover, so I wouldn't know what to point you at as the most likely causes on Rovers, just in general.