Renault Clio III 2007 1.6L 16V no O2 sensor signal

Oh no you have the same problem ! Nothing has changed

I thing my rear 0/2 pid also says -100% I think this is normal as ours runs good

There is no doubt that the car is pulling fuel away which creates your misfire code ,clearly in your last shot both o/2s are not agreeing !
I can't tell from your screen shot how long a time it covers but to be pulling away that amount of fuel when your front is showing lean is crazy how long a time does your pic/ screen shot cover ?

Is there any way your wiring harness could be plugged in the wrong way round ? Front in rear and rear in front ?conector

Don't think it's about the harness connected backwards, the rear o2 connector is waaaay longer to reach the sensor.

I'd say the time span of the screenshot is about 30s.

Yeah, feel the same way: all the heater issue seems to be a useless (well, lets say learning) detour.

Only thing I know is that sensors not agreeing with each other could cause an issue on Renault's thanks to the "double loop" feature.

Will try to do a better data capture tonight to see if other ideas come up!

Yeah sorry it wouldn't have given what you have

Can you delete the fuel data with your scan tool so your ltft goes to 0 sorry may have asked before ?

Well let's just say the double loop thing is causing your problem because the rear 0/2 is staying Rich ,if you short the rear signal wire to ground (while all plugged in using a jumper lead or test light with car running )pulling on your scan tool rear sensor to 0v ,you should see the fuel trims reduce in negative numbers as its seeing lean now and then go into positive fuel trims

Will try both ideas asap. I might have to lend the better scan tool from the tech I met recently to see if there are any manufacturer codes in memory. Shorting the rear o2 I can do to see the behavior of the fuel trims.

Any resources on what's a normal reading of a rear o2 with a good catalytic activity?

I've been told by another technician that he thinks I have a plugged cat judging from the amount of air getting out from the tail exhaust. Could be...?

If your cat was plugged I would exspect from a map sensed engine ,negative fuel trim numbers which you do have ,as the volume of air it calculates for is incorrect becouse if there's less getting out there is less getting in ,but the fueling stays the same ,hence rich condition but I would have exspected your rear sensor to have been lean ? Maybe I'm wrong on the rear sensor if the rest of the exhaust is blocked ?You could do a back presure test by removing the sensor and putting a presure gauge in the hole it should be less than 1 psi really .


Re your question On your rear 0/2 signal I would exspect around 650mv but we have to be mindful that yours is only slightly higher at 700mv BUT the car had -60 %on the fuel trims

Also with a plugged cat your intake vacuume would be low ,if you can borrow the scan tool check from the tec ,as if you remember we questioned the reading from the intake pressure before saying it was to high/ not enough vacuume but then discarded as we think your tool is including atmospheric pressure in its reading ,worth putting a vacuume gauge on the engine for sure if you have one 20 ingh is what we want to see on good engine

Had written an update but something went wrong while posting.

Here it is again: from the last test drive.





My thinking was almost like yours, except for the part where you expected lean at the rear o2.

With a plugged/degraded cat, it doesn't convert well, rear o2 reads high voltage (thinking its rich), PCM reads that and tries to reduce fuel gradually until the point where it's outside spec, creates the misfire due to lean mixture?

Also I noticed that the throttle body is back to a max of 60%, it was corrected with the better scan tool to have a max of 89%. Maybe it's some kind of failure mode?

Will go with the tech to get better scan data and do my best to confirm cat/exhaust issues. I might have to go to an exhaust shop to see if there is back pressure.

That MAP seems suspicious too, but I did some graphing and it seems to correlate with throttle position. Tech used carb cleaner around intake manifold and didn't seem to find a vaacum leak.

Oh well...

Images attached

Update: just saw this on expected rear o2 voltage at idling is 480mv.



I guess that means rear o2 is reporting rich?

And MAP reading at idle is expected between 240mb - 410mb.



Freeze frame at idle reported .44bar (440mb). Slightly above the upper limit. Exhaust restriction? Low compression?

I guess I have to figure out how to do a back pressure test. Either I find a gauge or find an alternative method.

Will report back as soon as I get more data.

Quick update:

Went to techs shop to see codes in memory. DF436 was there, deleted them. Told him about my theory of plugged cat. He suggested I take the car to an exhaust shop. Took it there.

The guy there checked and said he didn't see anything that suggested plugged cat from underneath. I asked if there was any way I could check from the inside, so he offered to take the cat down to see. Once down, we saw there are two honeycombs. The one on the front side was darker than the one behind. He then suggested he could take only the first one to see if that improved the situation.

On a desperate call (again), I took his suggestion. One hour later, no change at all. Even got codes for both o2s circuits. Deleted them and haven't reappeared yet, but vacuum and rear o2 sensors didn't improve. I'd even say rear o2 reading got slightly worse.

Fuel trims are still stuck negative.

Got back to scan tool tech and told him about that. He then suggested we do some test on Monday (compression test, adding pressure to coolant circuit) to rule out things like blown head gasket or possibly a engine valve damage or even slight timing offset.

Thoughts? Hate myself right now for the bad call on the cat.

Here's a pic of what the guy took off from the cat.

that was not good ! We just wanted a presure test to confirm or discount the cats

Let's start from scratch I'm sure I can help you solve this ,if I give you some checks if you do just them and get straight back to me ,there's a few things I need

1) since you've deleted the codes does your front and rear o/2 both end up pegged at 0 ?
2) your front and rear o/2 did not agree so we need to know which one is reading correct that's so important .if the front stays negative and the rear is high give it a good squirt of car clean while watch the front and rear o/2 and see if you can capture for me in the screen shot the result
3)I need to know how long a time your screen runs for on your screen shots ,so you have 10 numbers along the bottom can you adjust the time and if not time with a watch how long it takes for it to move from 1to 9 (10 is out of view) and from now put all info in graph view
4) when you run it and your problem is there back probe the signal wire of the rear 0/2 and short it to ground so we can see if the fuel trims are being forced into negative becouse of the rear o/2 signal

If you can do these we can move forward ,we haven't run out of things to check but you need the answers to these questions and be able to be sure of the results to move on ,becouse you could have more than 1 problem here but we need to know which o/2 to trust ,don't give up your not that far from beating this

Thanks for the support Chris!

I can only answer the first one right now: o2s doesn't seem to get pegged at 0 anymore, except for the moments where the CEL blinks, which has happened twice since the first memory wipe with the good scan tool.

And if it's useful, I've confirmed PCM is activating heaters on both sensors successfully.

Will do the rest and report back.

Ok good I have a few other things depending on your results

Random update:

Went to tech's shop. Performed two tests aimed at rule-out head gasket issues or compression issues.

1. Pressure test on coolant system: Added 15psi, left for about 10 minutes. Pressure dropped to about 7 psi, revealing a small fissure on the thermostat housing. Apparently no signs of coolant leaking into the combustion chamber. Valid test?

2. Compression test: not sure if this was a well performed test, but all 4 cylinders were in between 128psi - 145psi. I haven't found the spec for this engine. Still looking. Is that OK for compression?

www.dropbox.com/s/af04srohnztvxbr/File_000.mov?dl=0 -- a 5 times "crank" read reading about 135psi.

www.dropbox.com/s/1xal5jvaqlpio5o/File_001.mov?dl=0 -- not sure about this one and that "pop". he repeated the measuring on this same cylinder, read about 128psi (could record that take).

Can this by any change be related to the rear O2 reading issue?

Will try to do the other tests tonight and report back.

Your compression readings are good not excellent but they are the same as mine if not slightly better so no issue there ,couldn't really hear the pop sound very well on video but nothing is related to your 0/2

Report on tests requested:

1) No O2s pegged either way. They respond to events (not sure about the accuracy though).

2) Carb clean added seems to create a rich response in both O2s: www.dropbox.com/s/xiusn4f7bxcpn82/carb%20clean%20added.png?dl=0

3) Time the scan tool graphs per each pass: 12 seconds.

4) Here's a snap of what occurs when rear O2 is grounded.

Before: www.dropbox.com/s/ljytgj2fw3je849/before...0downstream.png?dl=0
After: www.dropbox.com/s/f9pxzzwz59f53sg/after%...ream%202min.png?dl=0

Will post some additional findings in another post.

Additional info 1/2:
When trying to add carb clean, I expected a lean response in both O2s as soon as I disconnected the hose. Instead, I noticed like the car was able to breath better (no hissing on the hose disconnected). Revs and Intake PSI seemed to be more consistent with the hose off. That made me question the air filter condition, so I opened the box, took filter out, and, although it seems to be OK, the fit seems to be too tight once I try to close the box. Can that be restricting air intake?

Intake hose just disconnected: www.dropbox.com/s/mb1ewke9ghu9bi7/vac%20...take%20hose.png?dl=0

Intake hose left disconnected for about 1 min: www.dropbox.com/s/8vmm83phs210hx9/hose%20disconnected.png?dl=0

I did a test drive without air filter (bad idea?) and noticed a better idle regulation, slightly better response with throttle open, but at high revs feels sluggish and the occasional hesitation.

Additional info 2/2:

Noticed that at higher revs sustained for more than 20 seconds, downstream signal slowly decreases, but when back at idle, signal climbs up again (slowly) upwards to around 750mv - 800mv:

www.dropbox.com/s/ht8evgqxl7lfyju/hi%20r...%20reaction.png?dl=0 -- If revs are sustained for longer, rear O2 voltage keeps decreasing down to about 600mv.

Air filter state and the hose I've been using to add carb clean / inducing vacuum leak: