207 1.4 Petrol with P0135 DTC

[mlkey]

Hello,

My son's car is showing the anti pollution fault occasionally. I checked it with planet and found P0135 (Front Heated Oxygen Sensor Heater Circuit) to be logged. This has been going on for some months and I checked the wiring as best as I could but did not see any obvious problems. I have changed the upstream O2 sensor to no avail. Does anyone have experience of this problem?

Thanks.

[CitroJim]

Check you have 12V at the oxygen sensor connector that feeds the sensor heater. 12V should be present all the time the engine is running.

Another way is to observe the sensor output on Planet. It should cyclically vary between about 100 and 800mV and start doing this virtually from cold as long as the heater is working correctly.

Does the AP fault come up when the engine has been idling for a bit? Prolonged idling will cause the sensor to cool off if not being heated properly. Also, if the heater supply is faulty it'll take a while for the sensor to start cycling from a cold start...

[mlkey]

Hi Jim,

Thanks for the reply. It occurs after a cold start only. An interesting but perhaps unrelated thing to note is that the light goes off within two key cycles of filling the fuel tank. It does not normally return until the fuel level is down to half a tank or below. I will check the feed tomorrow, I need to get hold of a wiring diagram from somewhere.

Regards.

[mlkey]

Did another planet session on the 207 this morning with a cold engine, watched the sensor voltage after starting the engine. It took at least one minute before it started to oscillate between around 100 and 800mv suggesting the heating circuit is not working. Does this now leave me with two possible outcomes having already replaced the sensor? I will probe the heater circuit voltage shortly just to be 100% certain it is not working correctly.

1. Faulty wiring.

2. Faulty ECU.

Would it make any difference at all to reset the adaptions?

Regards.

[citronut]

did you fit a universal sensor which you have to splice the wires to the original plug/loom,
if so these quite offten dont make a very good conection, i have had problems with these on several occasions, as have the garage i use for MOT's,
we will only use the sensors with the OE type plug factory fitted now,

regards malcolm

[mlkey]

No, it was an NGK sensor with the correct connection and wiring.