Technical NEW O2 sensor - P0136 again, 1.3 Volts?

[Diwiak]

Hi,

that Italian horse started to show warning light together with P0136 error - so I cleaned all the connectors, code remains. Lambda sensor changed for new one, and again same error after some short ride - cleaned all the connectors again, no change..

Any ideas? I am attaching screens from diagnosis which shows pretty high voltage - is cat converter goin?
I need to mention that I'm using fuel additive regularly and spark plugs been pretty dirty-black after some 15.000 KMs - could it be loosen carbon deposits clogging cat converter?

Thanks for idea, otherwise engine running fine, Punto '05, 1.2 8V, 44kW, almost 150.000 KMs done.

P0136: O2 Sensor Circuit Malfunction (Bank 1 – Sensor 2)

Warm engine:


Hot engine:

 

[Mike1alike]

There is a very easy and effective way to clean your cat. Here it is:

MAP sensor known good? | FIAT Punto (Mk2/2b)

Hi, Can anyone advise me what a ‘known good’ MAP sensor reading is at hot idle on a 2004 8v 1.2 engine? My scan tool shows 4.2 psi at hot idle (OBD2 data) which looks plausible but if someone could confirm that would be great. The reason for asking is that there are huge -ve fuel trims at...

www.fiatforum.com

I didn't do emission measurements before and after, but the engine runs better after I performed this cleaning. One clear thing I felt after is no lag when pressing the accelerator and before, there was 1-2 seconds lag.

 

[jackwhoo]

P0136 is code for post cat o2 sensor circuit.

If pre car o2 voltage is switching between about 0.2 v and 0.9 v when engine warm and ecu closed loop then engine likely to be running ok.

Post cat o2 sensor 1.3 v ! ..... check wiring for damage /incorrect connections

 

[Diwiak]

P0136 is code for post cat o2 sensor circuit.

If pre car o2 voltage is switching between about 0.2 v and 0.9 v when engine warm and ecu closed loop then engine likely to be running ok.

Post cat o2 sensor 1.3 v ! ..... check wiring for damage /incorrect connections

Pre-cat lambda seems to be working fine, I will be doing more testing next week and let know Iam busy till next week.
Could not be ECU related? What about dirty spark plugs?

 

[jackwhoo]

What brand spark plugs? Are they correct for engine?
Why Are you using fuel additive?
Where are you located?
Mostly Short journeys?
Thermostat ?
Coolant temperature sensor?
Etc

 

[jackwhoo]

Spark plugs worn out?

 

[Pugglt Auld Jock]

OP states pre cat sensor working fine? is this just a cursory observation or has someone put MES or similar on it and observed it's function? If indeed it is switching correctly then we can probably conclude that gasses going into the cat are within expected parameters? That being the case the downstream sensor, giving a high voltage reading means there is low oxygen being seen in the gasses leaving the cat? Post cat sensors are, by the nature of their positioning, slow to warm up and rely more on their inbuilt heater for help. I find myself wondering if the heater circuit is fully functional especially as this is a universal sensor which has had the plug from the old sensor fitted to it?

Anyone know if this engine uses the same sensor for it's pre and post car sensors? If so I'd be tempted to swop them over and see if the new sensor functions correctly in the precat role? I can't help feeling "worried" about the fact this is a "universal" replacement and would want to eliminate the sensor itself as the problem as I've had problems with these "universal" sensors in the past.

 

[Mike1alike]

Anyone know if this engine uses the same sensor for it's pre and post car sensors? If so I'd be tempted to swop them over and see if the new sensor functions correctly in the precat role?

Yes, the sensors are exactly the same, pre and post cat.
But, to swap them over, sometimes is tricky because one of them is stuck due to exposure to high temperatures. Usually the post cat one is.

 

[Pugglt Auld Jock]

Yes, the sensors are exactly the same, pre and post cat.
But, to swap them over, sometimes is tricky because one of them is stuck due to exposure to high temperatures. Usually the post cat one is.

May be in with a shout then as it's the post cat one he's been "fiddling about" with?

 

[judderbar]

As already mentioned the code is for a circuit malfunction. There is an ECU wiring colour code chart in the download section to help trace the wiring from the ECU.

 

[Mike1alike]

But it doesn't mean for sure that the problem is with the wiring. In fact, every time a sensor gets at the end of it's life, this is the code ECU gets, circuit malfunction. Because the sensor is also part of the circuit and being broken, it brakes the circuit.

 

[Pugglt Auld Jock]

Still "worried" about it being a universal sensor.

 

[Diwiak]

Hi,

sorry for late repsonse been busy,

measured all leads from sensor connector to ECU main connector, zero resistance, no shortage between them, measured voltage at sensor leads while connected with engine running (heating-white+white cable 12V, sensor itself black+grey up to 7V). While I disconnect heating leads (white) theres no voltage from sensor at all.
Then swapped sensors before / after cat, same values only reversed.

From this seems that O2 sensor is gone again after short time? Is there any chance that ECU/car electronics could damage O2 sensor? Or just bad luck and fresh new sensor is faulty from new (believed to be genuine BOSCH with attached connector)? Any ideas?

Thanks

 

[Diwiak]

SOLVED,

after replacing O2 sensor it is working now, no faults, MOT passed with no problems. So probably faulty sensor from new. Thanks for tips.