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

Hello there,

So I got into DIY automotive repair a few months ago. And, after a Cam belt job (which apparently went OK) and a cooling fan replacement due to motor pulling too much power, I am now stuck at an O2 signal issue.

Vehicle: Renault Clio III 2007, 16V 1.6L, manual gearbox.

Symptoms:
After about 7-10 minutes of a cold start, upstream O2 signal goes very low and even reaches 0V. Following that, downstream O2 signal starts climbing up to 1V and after a couple minutes both signals are gone. It seems they want to come back while the car is running, but very weak.

According to the manufacturer service manual, downstream O2 is used for a “double loop” mode. Check here: www.dropbox.com/s/n7e5ajqt65p0x27/RICHMA...MENT-DBLOOP.png?dl=0

Before I replaced both sensors, I had a downstream O2 heating circuit DTC. (P0141)

After replacing both, lost signal issue was present, but no DTC codes have appeared (at least yet).

One thing I tried was to do a test drive with the downstream O2 sensor disconnected, see if that disables the “double loop mode”. No luck, it just sets a P0136 and P0141 code, and STFT goes to almost 100%.

I have already followed almost all troubleshooting procedures related to O2 sensors circuits. Only thing I have yet to do is verify 12V on the upstream sensor heating circuit. I don’t believe that is the issue, since there is signal for a few minutes after a cold start.

Continuity tests on reference, signal, and heating circuit ground for both sensors did OK. 12V on heating circuit for the downstream O2 did OK too (but, with the engine off, just the switch ON).

I am just learning about voltage drop tests, and how to do a 12V to O2 signal with licked fingers (thanks to Paul’s videos) and verify if the computer reads something.

My suspicion is that it is a problem that only presents itself WHILE running (that is, when all the conditions to activate the downstream heating circuit are met — short circuit? damaged wiring?

What I’m trying to figure out next is for tests ideas on how to verify 100% the integrity of the wiring for both sensors BEFORE I have to undo all the wiring (connectors are located in a very uncomfortable place). Another constraint is that the PCM connectors make it very difficult to back probe specific pinks on its connectors.

I only have a very basic DVOM, and a generic OBDII Bluetooth dongle with a couple of Android apps.

Once I discard any wiring issues, I guess I have to move on to finding someone with a better scanner to see if there are any manufacturer codes set that make the computer behave this way.

Any help is appreciated. And please feel free to question any of the steps I’ve taken or if you need more info on the vehicle. I have the full set of Renault tech docs (wiring diagrams, PCM programming overview, etc.).

I’ll attach a couple of screenshots on computer readings before (cold start), just before the issue appears, and when the issue appears.

2-3 minutes after cold start: www.dropbox.com/s/is9f14jgu39kyjf/BEFORE-ISSUE.png?dl=0
Before issue shows up: www.dropbox.com/s/is9f14jgu39kyjf/BEFORE-ISSUE.png?dl=0
Issue present: www.dropbox.com/s/35gimeoh913ldmp/ISSUE-PRESENT.png?dl=0

Thank you very much guys!

Hey Albert! Sorry for taking so long to get back to you on this one.

I see what you mean about the upstream O2 signal flatlining... Do you notice any lack of power or misfiring once this happens? Also, do the signals start behaving normally again once you start driving down the road?

I'm more than happy to help you go through testing wiring integrity, but the first test that comes to my mind when I see the flatlined O2 is a response test. Once you see the upstream O2 drop out and the fuel trims climb, add some external fuel to the intake and see how the O2 responds. You SHOULD see the O2 signal climb above 800mV and stay there the entire time you're adding fuel.

This SD video shows the concept. Scroll to around 12:40:



If you get the correct response from the O2, then I'd suggest that you do NOT have an O2 problem, and we need to look elsewhere. If you do not get the correct response, then we'll dig deeper into the O2.

Hey Tyler! Thanks for replying.

I get some random misfiring when this occurs and the PCM sends the STFT to 99%. Before flatlining, everything seems to run OK.

I'll try to do the test as soon as I finish assembling the car again.

I got desperate and undid the wiring harness trying to find any kind of wiring damage to any of the sensors. No luck so far, at least with nothing visible. Only thing I'm concerned is that I couldn't reach to the last part of the wiring for the downstream O2, it's behind the firewall and it has an unreachable clip that prevented me from pulling the cables so I could inspect them.

My main concern is having a bad PCM driver (downstream O2, ground control). I intended to do some kind of testing at the PCM connector, but the kind of connector it uses makes it really difficult, and I don't know how to safely disassemble those. Picture: www.dropbox.com/s/wtqubs1j193cza0/PCM-CONNECTORS.jpeg?dl=0

Other ideas I have in mind:
- Refitting a different O2 from the ones I replaced? I put new sensors in both positions, but maybe I got a bad new one and this is throwing me off?
- Checking for amperage or a voltage drop testing at the downstream heating circuit? I've read 12V twice at the connector, but that might not be the case with the sensor connected.
- Some weird code set at the computer, unaccessible with my scan tool is protecting the circuit from a previous issue?

I'll report back as soon as I get some new data.

Once again, thank you for your help!

Oh, and by the way, I noticed I put the wrong link for the "2-3 minutes after cold start" picture. Here's the proper one: www.dropbox.com/s/q2abp88r4vnpilg/COLD%20START.png?dl=0

Hi just thought I would chip in a little if that's ok ,just a few thought I have a Clio 3 on a 59 plate but it's the 1.2 100 bhp model ,I've been working over several problems I've had over the last few years and a few things I found .
1) I had bad earths on the car and found that if you put the blower motor on and heated rear window it would flat line the o/2 sensor ? I cleaned all earths up inc the pcm ones behind the bat and this solved the problem .2) I use a snap on solus ( scan tool )to command the heaters on the o/2 on but the tool commanded the oppersite 0/2 heater to the one selected which trough me through a loop for a bit ,just a software issue with the tool but worth remembering if you use a tool to command the heaters on .3) with this car the rear o/2 sensor heater does not start until car reaches operating temp and on warm up I have around 25%+ stftfrom cold on the front 0/2 until worm .i do have other problems with the car but believe this to be correct

Oh forgot to say the heaters on mine draw 0.5 amps there ground side switched 12v

Hey Chris, thank you. Glad to know I'm not the only one with a Clio here.

I'll take a look for any dirty earths as well.

Does your scan tool has bi-directional comm? It'd be really useful to have the heater activated by a scan tool instead to verify. As you say, the service manual troubleshooting indicates that the downstream heater is commanded ACTIVE until engine is warmed up and you do a small drive, which makes it a little trickier to test.

I have yet to find a good resource on how to check for amperage draw without damaging the PCM!

Hi yes the solus doesn't have great bi directional controls for this Renault ,It has great control on other cars like my partners 2013 Peugeot rcz its quite a good all round tool ,but it does turn on the heaters on the Clio although the wrong one as I said .i use an amp clap to check the current for everything ,I use my amp clamps that I have with my pico scope ,you can also use these with a multimeter with a little adapter . I doubt it's an earth problem but as you know the renaults are known for bad earths my partner had the Megan before this Clio and that was the same .i notice from the pics the conectors from the Ecu are slightly different to ours but sure they come apart

Hi again sorry just read your post again and our Clio only starts the heater on the rear once up to operating temp not sure if this changed on our model or there's a problem with ours ,but I know for sure that's the case with ours .just thought I'd clarify thanks Chris

Thanks Chris,

I did clean up all the earths I could access around the PCM area. They looked fine before I took them apart.

Here's what happened in the last two days just after I finished reassembling everything.

1. I wasn't able to get any propane to do the O2 response test. And even if I did, Im not quite sure where should I put the propane into. Does it has to be before or after the throttle valve? Before or after the air filter? There's a vacuum hose that goes to the brake booster (I think), not sure if that works.

2. I did finish reassembling the wiring as it was before I took it apart. As I think I said before, upon visual inspection, none of the heater wires seem to have any damage on them.

3. I did test the rear O2 by grounding the heater circuit. It resulted in a quick climb to around 800mv on the scan tool, wit the occasional slight oscillation. For what I understand, this is expected and indicative of a healthy catalytic converter. Of course, as soon as I disconnect the ground, voltage goes back down to around 470mv. My interpretation is that the O2 is good, signal circuit is good (I tested that before following Paul's advice) and it has good voltage. Am I missing something here?

4. I tried measuring continuity from rear O2 heater ground to battery ground but didn't get any. Don't think this is a valid test because I'm not sure conditions for the PCM to command the heater on were met. I let the car warm up but still nothing.

After all of this, I'm still not sure if there is any wiring problems at all.

- I followed this procedure before, and everything seemed OK with continuity from the PCM to the heater ground. What I'm not sure is that if continuity test is enough to discard a wiring issue? Here's the procedure: www.dropbox.com/s/3bcyx5r42hnbjvm/DF602%...UIT%20FAULT.png?dl=0

- Was thinking of doing some voltage drop testing to verify there is no resistance in the O2 heater ground wiring, but, again, no way to make sure conditions for commanding the heater are met. Maybe if I ground it directly, can I still do a voltage drop test? How?

- Maybe is there another event during the driving cycle that is bringing the signal down? I still think it is a heater issue, since if I run the car without grounding the heater, it seems to warm up very slowly, like with the exhaust gases heat instead.

- Any conclusive test idea to discard a bad PCM driver?

Thanks for your help and patience guys!

hi again i couldn't see a reply from the administrators so happy to help the best I can it maybe a bit disjointed but I write as I think of it
Re adding propane ? So the idea is that as your front 0/2 sensor is pegged lean (0 volts ) if we add a fuel source we hope to see the sensor react ,this would prove if the sensor is active ,we would also look at the stft .at the moment from your pics the stft is high ( adding fuel as it thinks it's lean 0v)as its trying to move the 0/2 signal back to its normal range and to get it switching from say 0.2 to 0.8 . I use carb clean myself as a fuel source but you can use propane as well .this can be added into the intake or vacuume hose that goes into the inlet manifold the only thing to note is that if it has a MAF sensor it should be put down stream of this so the fuel doesn't damage the sensor , I think yours just has a map sensor so should be fine in the intake also although not related worth Noting best not to use starting fluid as a diagnostic tool as its a bit to volatile .
Re fitting new 0/2 sensors did you use plug in type or are they universal so called sensors ?that you wired in ?
Another question I have is when you grounded the heater of the down stream sensor (activated it)what happened to the front sensor / fuel trim ?
One thing when looking at the 0/2 sensors when you have an issue is working out if one is lying ? Can we believe the value ,By that I mean if your front is saying 0 volts (lean condition) but your rear is at 0.8 volts then there not agreeing as if your front is pegged lean for some time and there is really a lean condition you will see that the rear will also be lean . And as such on a working / good car if you add fuel into the intake you want to see the switching signal of the front o/2 go immediately high meaning it's seeing the fuel and with a short delay this fuel should be seen also on the rear 0/2 . this delay is also used as one method to see if the cat is working

So in your case I would start her up get her warm look at both o/2 sensors only on your scan tool so the tool react quickly if as you say the front goes lean add some fuel and see How it reacts ? If the front reacts straight away and your stft counters buy reducing ( removing fuel ) then it would seem the front 0/2 sensor and wiring and pcm's reaction are good for the moment .look at the same time at the rear does it also react ? Now the rear o/2 sensor as you know shouldn't switch back and forth like the front but stay steady but should react to fuel added or for that mater extra air ( vacuume leak ) .now from what you say when you heat the rear 0/2 (ground it out ) it says 0.8 v if you do this so the rear is working do you see the reaction on the rear as well as the front ? When the rear is heated and reading 0.8 and with no addition fuel added what are the fuel trims ?

Oh one question I remember you asked is about doing a ground to ground voltage test on the heater this would be a valid test if the Ecu is grounding it at that moment otherwise that ground is not connected .if you ground it yourself then your testing the difference between your added ground and the neg battery lead which your not wanting

Hope i made sense so far Chris

Oh forgot to mention I'm just a diyer like yourself but trying hard to learn from Danner ! Oh and Please Tyler if you read my last post and I messed up please chip in and correct me Oh and sorry I think I upgraded you to administrator or is that down graded not sure how it works thanks Chris

Thanks Chris!

The front o2 seems to work fine. It oscilares from 100 to 800mv as it's supposed to. And if I snap the throttle open, it responds accordingly. And it doesn't take more than a minute to heat and starting the closed loop action. I haven't paid attention about the fuel trims but on first sight they react accordingly as well.

The issue is that the front o2 lost signal but it seems to be AFTER the rear o2 gets heated by exhaust gases and climbs upwards 800mv (maybe more), but when I grounded the heater, this didn't happen.

It didn't even ser the P0141 code in the 20 minutes it was idling.

My theory was that when the PCM detected an anomaly on time it takes to heat the rear o2, sets the code and cuts ground to both heaters to protect itself.

By the way, o2s are original OEM, no rewiring was necessary.

Will try to do the propane test to see what happens, but i still thinks it has more to do with something preventing the PCM to command the heater ON.

Thoughts?

Hi you say the front lost signal by that I'm guess you mean pegged lean 0 v ? Buy adding the fuel at that moment you would confirm if at that moment the sensor is still operational and able to move and not shorted to ground .
From what you said I would have said that when the rear 0/2 comes on line it reports a rich condition (high voltage ) and the car reduces the fuel creating the lean front 0/2 BUT ! You say not when you ground the heater ? So are you saying if you ground the rear heater the front continues to switch normally ? And car run fine ?

Just re reading you last post ,re your theory ?,sorry are you saying that at the moment it will and is setting the p0141 code as I though you had said that the new sensors had stopped that code setting ?

ChrisG wrote: Oh forgot to mention I'm just a diyer like yourself but trying hard to learn from Danner ! Oh and Please Tyler if you read my last post and I messed up please chip in and correct me Oh and sorry I think I upgraded you to administrator or is that down graded not sure how it works thanks Chris

You're good! No corrections needed, as far as I can see.

albertdrake wrote: Thanks Chris!

The front o2 seems to work fine. It oscilares from 100 to 800mv as it's supposed to. And if I snap the throttle open, it responds accordingly. And it doesn't take more than a minute to heat and starting the closed loop action. I haven't paid attention about the fuel trims but on first sight they react accordingly as well.

The issue is that the front o2 lost signal but it seems to be AFTER the rear o2 gets heated by exhaust gases and climbs upwards 800mv (maybe more), but when I grounded the heater, this didn't happen.

It didn't even ser the P0141 code in the 20 minutes it was idling.

My theory was that when the PCM detected an anomaly on time it takes to heat the rear o2, sets the code and cuts ground to both heaters to protect itself.

By the way, o2s are original OEM, no rewiring was necessary.

Will try to do the propane test to see what happens, but i still thinks it has more to do with something preventing the PCM to command the heater ON.

Thoughts?

Interesting... The upstream O2 only flatlines after the downstream O2 becomes active... :huh: Just to be clear, you're not getting any codes with everything hooked up?

Thoughts... Perhaps this is intentional? I'm not sure exactly how this 'double loop' system works, or how it tests itself, but the O2 behavior may be part of it's normal testing routine. I'd be interested to know what the Loop status is during this time, i.e. open loop, closed loop.

It'd also be good to know what the fuel trims are doing when the upstream O2 drops lean. Watching the trims climb positive during that event would suggest that it's NOT intentional, and the PCM is correcting for something it didn't anticipate. Watching no fuel trim correction would suggest an open loop condition, and some kind of test taking place.

The other thing I was thinking of is o/2 heater inducing voltage to signal ,if by the trims the Ecu is cutting fuel because of the rear being high I would out of interest ground the rear heater with key on engine off and see if there's any rise in the signal voltage

Question for Tyler ....Just looking back at the original post and intake psi as its listed which must be from the map sensor is 5 to 7 ish psi ?asuming this pid is accurate This should be vacuume and with ltft - 70 odd ?. so the car is seeing high voltage on the map ,over estimating the amount of air ,fuelling accordingly ( more air more fuel )creating a rich condition and hence the taking fuel away ?

Will try to answer all of the questions:

- yes, if I don't ground the rear o2 heater, the front o2 signal gets pegged to 0v and occasionally tries to unstick, but doesn't last long. Considering the timing, this happens only after the rear 02 voltage rises to above 800mv.

- Rear O2 voltage rises too slowly after engine gets warm, thus makes me think this is due to exhaust gases only and not a signal as such. If I ground it, it rises in matter of seconds, and it seems operational responding to throttle, have yet to induce a response with propane).

- while the rear O2 is grounded, front O2 remains operational. I tried to replicate the issue while the rear o2 was grounded but even after 20min idling, I couldn't. And I expected to see any codes set again (I erased them before starting the engine, but they didn't). My guess is that if I don't ground the heater and let the car idling up to the point the rear o2 gets warmed up by exhaust gases, codes would reappear.

- When the issue is present, STFT gets pegged real high, from +75 to +99%, this makes the engine run real rough.

- I suspect about the map myself too. I dropped it a couple of times while trying to replace a broken oring that made it fit loose. Haven't looked into it yet because the reading at KOEO (engine off) matches ambient pressure. I don't have any reference values to it unfortunately.

I appreciate any other ideas or input from you guys. Will do the propane response test as soon as I can. Any further detail that you think would help let me know.

Thank you very much!

Forgot to mention: it doesn't seem something the PCM anticipates because the secuence goes something like this:

- cold start, after about 30-40secs, front o2 starts oscillating between 100 and 800mv.
- STFT responds to the front o2 readings
- engine gets warmed up to operating temp.
- 2-3 min after, cooling fan kicks in, and this is about when rear o2 voltage starts rising from 450mv to more than 800mv, this takes about 4-5 min to happen.
- once rear o2 voltage climbs up (and stays there), it takes about 2 min for the front o2 to loose signal
- with front o2 signal at about 0v, STFT climbs to 90% or more, and stays there for almost a minute until the check engine light blinks, and then fuel trims get set at STFT 14.1 and LTFT 0, once it stops blinking, fuel trims get out of whack again.

Hope this helps (and will re-validate asap).