Citroen C1 Mk2 2014 - Oxygen Sensor - Help Please!

[gdbarratt]

Citroen C1 1.0 Feel 68bhp 2014 but an early Mk2
Original Error
PO141 – Heater Oxygen Sensor (HO2S) 2, Bank 1, Heater Control – Circuit Malfunction
Engine Warning Light and then TPS Malfunction Warning Light
I replaced with Lamba Sensor CFB (1KR) Oxygen FPUK Quality from Parts in Motion
Reset error codes and all seemed fixed but then on a long drive the dreaded engine warning light came back on but this time with TPS and VSC.

Error now is –
PO137 – O2 Sensor Low Circuit Voltage Bank 1 Sensor 2

Fuses fine, wiring looks all ok.

From cold –
2 Bank 1 Voltage climbs up to 1.275v and holds for 2 mins
3 mins 0.505 then 0.055
4 mins 0.000v
If you rev engine, then it does come up to 0.045v at most. Car does not show an engine warning light at this point but code reader can see PO137 which is correct as a low voltage reading.
General suggestions seemed to be the heater power to the O2 sensor (fuse or wiring) this all looks ok and when cold the voltage climbs to 1.275v and holds which suggests the heater is working but then after running engine for 3 minutes starts to plunge and is at zero by 4 mins. You can rev engine hard and max reading is then only 0.045v which of course is excessively low and leads to error P)137 and after long run warning lights.

Car runs absolutely fine regardless of fault, smooth pick up and power delivery same as always. The hill hold seems to fail when the warning lights come on but I get no other error than that above and once got PO139 which is sensor slow to respond.

I am stumped, any ideas please??
Anyone know a good Citroen specialist in the Congleton Cheshire area who maybe able to help?

[mickthemaverick]

When you say the sensor wiring looks OK, do you mean that testing from the fuse to the sensor gives a consistent resistance reading, or do you mean you can't see any physical problems with the wiring? I would suggest a clean of the contacts on the sensor and any connectors in the circuit as a next step.

[gdbarratt]

I have checked the connection of the sensor to the wiring loom and then followed the wiring to look for any damage which I could not see. That is the limit as I don't have a multimeter and also could not identify from the handbook the exact fuse so check all fuses manually of 20 or 30 marking.

[PaulC5]

Plug in the old sensor and see if it goes back to the original fault. If so then possibly the new sensor is not good enough and you might even be able to return it.