Technical Lambda issues 1.2 8v

[puntodeltathema]

Hello folks. Bit of a yuletide puzzler. Have done a bit of research on the forum but whilst similar issues come up, typically on the 8v engines, a definitive solution seems elusive....

2018 Panda 1.2 8v. Originally presented with intermittent hesitation. Error codes P0132-12 (Upstream O2 sensor short circuit/high voltage) and P0136-23 (Downstream O2 sensor "stuck low" / low signal). I initially thought the latter might just be a symptom of the former.

After a bit of a delay, during which the car continued in use, I came back to this and only the upstream short circuit code persisted, though it hadn't happened for a month and the error was stored. Driver (not me) reported it seemed to have been running a "bit better".

No Engine Management Light on at any point (MES says the EML is not triggered for these errors. Not sure if that changes if they persist beyond a certain point).

So, thinking a potential shot circuit in the upstream sensor wasn't good I have replaced the sensor with a correct new item (noting the Euro 6 sensors are different from the Euro 5 ones, and different up- and down-stream). Albeit I did have to resort to a Lucas item .

Car now seems to be running fine but I connected my scanner up during a run to look at the live data for the sensor readings, and periodically and randomly the upstream sensor falls to 0v. Maybe about every 5 mins or so for say 60 seconds. Always returns to an expected signal though up to 0.8v and fluctuating. Downstream sensor fine, typically in the 0.7-0.8v range and stable at constant throttle input. Previous downstream error has not reappeared. Car continues to run fine during the 0v episodes.

Intermittent P0130-23 code is now being stored (Upstream sensor "stuck low").

Thinking about it, the fact I have had intermittent errors affecting both sensors (and the fact a voltage-generating Zirconia sensor could not (I think?) generate a material short-circuit internally?), all of this must point to a wiring issue? I have had the ECU plugs apart and worked a bit, and the sensor plugs appear fine (it's only a 5 year old car after all), but.....

I will probably try cleaning as many connectors and earths as I can, anyway.

Or is this likely to be an ECU issue - unheard of I know for the excellent Marelli EM system (the irony may not have come through there in writing )

Just wondering if this triggers any thoughts over the sprouts... Thanks, and a Merry and fault-free Christmas to all

Nick

 

[bugsymike]

Only thoughts, but I did have to repair daughters 06 Grande Punto 1.3 multijet some years ago due to a rotted wire within the plastic sheath a couple of CMs (1/2 inch to me) from ECU socket, only eventually found by pulling on the appropriate wire and feeling it "stretch", the original fault was no trigger feed to the fuel pump/starter relay.
I bought car for £300 as a non runner, previous owners "mechanics" had fitted a new battery and starter, but worst of all towed it repeatedly which caused the crank pulley to slip as a pinch fit/freewheel design causing the valve timing damage. All for a rotted wire!!!

 

[Herts Hillhopper]

Only thoughts, but I did have to repair daughters 06 Grande Punto 1.3 multijet some years ago due to a rotted wire within the plastic sheath a couple of CMs (1/2 inch to me) from ECU socket, only eventually found by pulling on the appropriate wire and feeling it "stretch", the original fault was no trigger feed to the fuel pump/starter relay.
I bought car for £300 as a non runner, previous owners "mechanics" had fitted a new battery and starter, but worst of all towed it repeatedly which caused the crank pulley to slip as a pinch fit/freewheel design causing the valve timing damage. All for a rotted wire!!!

This ‘proves’ my long-held view that fault codes are often not right, and that more often than not the issue is ‘mechanical’ failure (eg a broken wire) rather than a failed sensor. Or, a problem of supply voltage (below par battery). Trouble is, these days most repair shops’ first port of call (hmm) is the code reader, and then a total reliance on what that tells them. Yes, they can give a clue, but often not pinpoint the problem.

 

[A3jeroen]

Often changing a sensor, cause it is mentioned in the faultcode is like shooting the messenger.

gr J