When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Also I can confirm a non ECU o2 sensor communication issue.
With the OBD connector hooked up and a spare o2 sensor plugged into the engine harness I can confirm it will register difference in oxygen (using the gas burner on the tip of the o2 sensor method).
I have 2 spares but one is very quick to respond to lack of oxygen, the other slow. So I guess it's two new o2 sensors to start with.
The X300 titanium O2 sensors are different in the resistance changes with 02 content . They will not generate a voltage like the more common type but the ECU supply's a 5.0 reference voltage and gets changed as it returns to the ECU as a value .
You can see this change of resistance ( and not voltage generated ) with a flame test once the sensor gets to operating Temp with a digital meter . Your device is probably not manually configured with the proper parameter ID and is on a default configuration to see the more common O2 sensor type
Last edited by Lady Penelope; 07-22-2018 at 12:25 PM.
The X300 sensors are different in the resistance changes with 02 content . They will not generate a voltage like the more common type but the ECU supply's a 5.0 reference voltage and gets changed as it returns to the ECU as a value .
You can see this change of resistance ( and not voltage generated ) with a flame test once the sensor gets to operating Temp with a digital meter . Your device is probably not manually configured with the parameter ID and is on a default configuration to see the more common O2 sensor type
How does.that work then. Especially with cold start as I have cold start issues and if I'm reading your post correctly they don't come into play untill up to temp. I also assumed O2 sensors are out of the loop until it's closed so paid them less mind. Is that correct?
Either way what I am seeing with the flame test executed as follows: little gas torch on, o2 sensor plugged in to engine harness held in long handled vice grips (tested both banks O2 "port") turn ignition on and observe o2 voltage meter through OBD Bluetooth reader in Torque app. I figured this way i couod test the harness and ecu are working and it all seems to be. In that my original sensors aren't responding to a gas burner heating the tip while plugged in the harness AT ALL and the "new used" ones are, if not slightly inconsistently. My OBD reader then shows reference voltage between 0 and 1.2 volts at a maximum. Mostly around .4 to .8 and in between.
Lady P am I to conclude this is or is not effecting things? Are they or are they not faulty? They don't start doing much until they are literally red hot.
Thanks.
Last edited by scuby; 07-22-2018 at 12:35 PM.
Reason: Stupid autocorrect
You are correct . You are seeing something as a response . Being the right number value or not is a different issue
The originals may have been the wrong type . The correct sensor connector hookup is important as they can be swapped . You have to look at the 4th unlike wire toward direction to the ECU .as the brown or green wire .
Last edited by Lady Penelope; 07-22-2018 at 01:23 PM.
You are correct . You are seeing something as a response . Being the right number value or not is a different issue
The originals may have been the wrong type . The correct sensor connector hookup is important as they can be swapped . You have to look at the 4th unlike wire toward direction to the ECU .as the brown or green wire .
by the looks of it I only have downstream sensors. Making sure Left and right are plugged in correctly using the U or R wire (red or bleu) wires as reference. Gotcha.
1. I'm sorry to hear that, I really am. I want to make sure you've tried to switch plugs, on the off chance that someway, somehow, Oxygen Sensor Bank 1 was plugged into the Bank 2 harness, and vice versa. It would be worth a quick try, although I'm sure you've tried that.
2. I have to believe it's the ECU at this point. Unless you have a major crack in your exhaust manifold, I can't imagine anything downstream of your engine causing a flat oxygen sensor. There is a guy in California that has fixed mine. I'm sure he can fix yours. Let me know offline if you're interested and I can send you the details. I figure it will run you about $400US once it's all said and done with shipping. Either that, or see what you can find on eBay? I think the x300 ECUs are not uncommon to come across?
3. Lastly, if you haven't done so already, I thought a continuity test for all the wires at both the sensors would be useful, but I can't figure out how they would both fail the same way, unless a common incident damaged two of the same wires at the same time? Seems rather unlikely. Still, using a multimeter to check for continuity is also free.
3a. I'm not sure which wires you have, but both oxygen sensors have common colored wires that are spliced to each other, I suppose if the splice became undone, it could cause mystery problems? Another reason to do a continuity test. Blue/Brown, Blue/Purple, Blue/Pink and White/Brown are all spliced together. If doing continuity test, check to make sure each set of colors is tied to each other as well. From the ECU, you should be able to take a reading at both Blue/Pink wires at both sensors, and so on. The single colored wires, are not spliced.
4. Lastly Part 2 - Has the EMS Power Relay been checked? It is tied to your oxygen sensors, although I imagine other things would be wrong too? It's in the passenger side dash, just below the airbag. It should be a light blue relay with a white plug. It's simple enough to swap that out with any other relay on the car, just to see what happens.
There's nothing, that I can think of, that should be able to cause your oxygen sensors to flatline.
1. I'm sorry to hear that, I really am. I want to make sure you've tried to switch plugs, on the off chance that someway, somehow, Oxygen Sensor Bank 1 was plugged into the Bank 2 harness, and vice versa. It would be worth a quick try, although I'm sure you've tried that.
2. I have to believe it's the ECU at this point. Unless you have a major crack in your exhaust manifold, I can't imagine anything downstream of your engine causing a flat oxygen sensor. There is a guy in California that has fixed mine. I'm sure he can fix yours. Let me know offline if you're interested and I can send you the details. I figure it will run you about $400US once it's all said and done with shipping. Either that, or see what you can find on eBay? I think the x300 ECUs are not uncommon to come across?
3. Lastly, if you haven't done so already, I thought a continuity test for all the wires at both the sensors would be useful, but I can't figure out how they would both fail the same way, unless a common incident damaged two of the same wires at the same time? Seems rather unlikely. Still, using a multimeter to check for continuity is also free.
4. Lastly Part 2 - Has the EMS Power Relay been checked? It is tied to your oxygen sensors, although I imagine other things would be wrong too? It's in the passenger side dash, just below the airbag. It should be a light blue relay with a white plug. It's simple enough to swap that out with any other relay on the car, just to see what happens.
There's nothing, that I can think of, that should be able to cause your oxygen sensors to flatline.
There is simply nothing more frustrating that putting the time in. The effort. Feeling and thinking you are being thorough.
This engine is quiet as can be, no sounds of a leak. Just pulled off the manifold cover. both manifolds have a huge depp cavernous crack. I'm deliberating finding a good set to replace. I can imagine this would throw off the values. Why the car would run rough in open loop I don't know though. I don't believe replacing the manifolds will remedy all the problems I'm having. They are pretty bad though.
At this point I need to think if I don't want to just cut my losses. I need the space and have far too much time and money into this car for it to be worth it. Of ocurse, I'm past the point of no return. But man, ever feel just beaten by a car?
There is simply nothing more frustrating that putting the time in. The effort. Feeling and thinking you are being thorough.
This engine is quiet as can be, no sounds of a leak. Just pulled off the manifold cover. both manifolds have a huge depp cavernous crack. I'm deliberating finding a good set to replace. I can imagine this would throw off the values. Why the car would run rough in open loop I don't know though. I don't believe replacing the manifolds will remedy all the problems I'm having. They are pretty bad though.
At this point I need to think if I don't want to just cut my losses. I need the space and have far too much time and money into this car for it to be worth it. Of ocurse, I'm past the point of no return. But man, ever feel just beaten by a car?
I've had cracked manifolds on my car. They didn't really create any problems. I did replace the manifolds, found new long ago, but I'll tell you that I do not believe this will solve your problem. I wonder if it would be worth your while to plug the existing manifolds with some Extreme Heat JB Weld, or similar. Should be a good temporary fix, at least to see if it fixes anything.
So what are the Short Term Fuel Trims and O2 Sensors doing with the new manifolds fitted?
Are STFT still stuck at 25%? - that seemed to line up with the manifold cracks you discovered - ECU permanently adding fuel to compensate for extra O2 in exhaust , O2 sensor flat-lined, and really causing overfuelling/stalling.
If STFTs are now moving and O2 sensors oscillating that would be a big step forward.
Although O2 voltage is physically 0 - 5V it's reported in range 0 to 1 by ECU and I never figured out if 1 is rich and 0 lean or vice-versa, but should be oscillating several times a minute.
From video the voltage is slow to rise on start, and is struggling to stay up at normal idle 500-800 rpm, hard to know if that's cause or effect. My recent stalling at idle issues had similar voltage drops/fluctuatons at idle when cooling fans kicked in.
Solved by a few things
My upstream O2 sensors were connected reversed - STFT were stuck at 25% , long term over-fueling led to black/fouled sparkplugs and struggles at idle I think. New plugs and swapping O2 connections the STFTs immediately started varying
(but your original plugs looked good I see)
Alternator belt tighten and cleaning of all bulkhead battery power studs and engine bay grounding points - got me an extra indicated 0.5 V somewhere along the line
Long shot on high idle- what about throttle cable adjustment - both pedal to traction-control actuator and actuator to throttle body if you have traction control? I see you replaced TPS and had calibration done so you probably already checked the TP range from idle to pedal to the metal via OBD.
With ignition on and engine not running you can measure full TP range on OBD.
I had to adjust mine recently as max OBD Throttle Position reading was only 80% with foot to the floor, but I ended up a little too tight (trying to get to 100%) and it would stick at TP 18% sometimes with foot off the throttle and idle high - bouncing the pedal sometimes relaxed it.
After backing off a little I now get consistent 12% at idle and 94% at pedal to kickdown.
If cable is good but idle TP doesn't get down to around 12 or 13% the the TPS calibration would be suspect to me.
ECM controlled relay also worth a check as it powers fuel injectors I think - can be swapped with Fog light or Low/High beam relays to test
Lot's of codes. makes sense. I'd messing with a lot. Reset the bunch. Still ran rough on startup. Found two dodgy coils. A little better.
1.5 hours later and a 3.2 ecu swap later, it ran well but had fast hunt at idle which settled down.
Long story short I'm looking for a 4.0 Euro ECU WITHOUT smog pump or EGR.
My ECU HAS smog pump and EGR programmed in. It's looking for feedback from those systems and isn't getting it as my car wasn't deliverd with them. There's no plumbing or wiring for them.
A suggestion. Are your O2 sensors new? Were they connected to the correct socket and exhaust tube? I had this problem after new exhaust fitted, car ran rich and voltage was1.2v at best, swopped the two connectors over and there was an immediate change down to 1.0v. The sensors are linked to cylinders 1-3 and 4-6 if connected wrongly the ECU tries to correct but is dealing with the wrong sensor.
A suggestion. Are your O2 sensors new? Were they connected to the correct socket and exhaust tube? I had this problem after new exhaust fitted, car ran rich and voltage was1.2v at best, swopped the two connectors over and there was an immediate change down to 1.0v. The sensors are linked to cylinders 1-3 and 4-6 if connected wrongly the ECU tries to correct but is dealing with the wrong sensor.
o2's have been replaced twice now if memory serves. they are new.
Replaced with one off a parts car. Starts and runs like a champ. replaced ECU from same parts car too. The main culprit for irratic idle and general misery was the MAF. The cause of high idle is the ECU. Also my old ECU was faltlining the o2's.
New ECU is not. I can see them working.
However I now have an opposite problem to how this all began. It began with high Lambda readings and all others fine.
Now I can see the ECU working. upon startup the readings are textbook. Lambda around 0.98 and o2 around 0.200 or so. Suddenly (without any noticable change in engine operation) the 02 skyrockets and the lambda plumits.
Here's an example of O2 behavior against secondary air and fuel status open/closed on startup and short run from my XJR6. It has 4 O2 sensors but I'm only showing 2 upstream here for clarity. Looks like my bank1 sensor 1 might be a little sluggish compared to bank 2 but I think overall this represents expected behavior
07-22-2018, 05:34 AM
