O2 Sensor Error Code 309

[pimenas]

Hello, I'm receiving the following error code on an F650GS twin spark, 2006 model (single cyl):

309: Oxygen (Lambda) Sensor Heating Circuit Malfunction, Signal implausible.
The fault is currently present.
This problem occurred once.

I tested the o2 sensor:
- Heater resistance measured 9-10 Ohm
- Signal seems to work, using a voltmeter, o2 sensor disconnected, engine running and warm, signal measures ~0.9V.
- Checked wire harness, seems ok, all o2 sensor pins were found on the BMS-C connector with no resistance.

What do you think, could it be that the resistance is too big (according to realoem.com the O2 sensor heater resistance is 6 Ohm), and the sensor is faulty after all?

[WayneC]

It would suggest an intermittent connection to the heater circuit to be considered "implausible" so either there is a problem in the 02/wiring or the output IC in the BMSCII is faulty. Failures i the BMSCII are rare but always possible

[pimenas]

Thanks WayneC,

The error says at the end 'Signal Implausible', so maybe it's referring to the o2 signal instead of the heater. Now one thing I forgot to mention is that while testing using the GS-911 I saw the lambda signal going from ~0.450V to ~0.650V and it pretty much stayed there when warm, and also closed loop was active. When disconnecting the o2 sensor and probing it with a voltmeter the signal was ~0.9V, so there's a clue that the BMS doesn't report the o2 signal correctly.

Now the bike has 90.000 klm on the clock, and it seems to run fine otherwise, so maybe I'm gonna try with a new O2 sensor and see where it goes from there.

[WayneC]

The error says at the end 'Signal Implausible', so maybe it's referring to the o2 signal instead of the heater.

I doubt it

Now one thing I forgot to mention is that while testing using the GS-911 I saw the lambda signal going from ~0.450V to ~0.650V and it pretty much stayed there when warm, and also closed loop was active.

That is as it should be but be aware of the fact the 02 takes 300ms to react

When disconnecting the o2 sensor and probing it with a voltmeter the signal was ~0.9V, so there's a clue that the BMS doesn't report the o2 signal correctly.

No it is not incorrectly report the signal, it should be around 0.9v when measured open circuit

Now the bike has 90.000 klm on the clock, and it seems to run fine otherwise, so maybe I'm gonna try with a new O2 sensor and see where it goes from there.

The 02 will often slow down in operation with age and particularly if the tip has considerable carbon build up, life is expected to be around 120,000 kms

[pimenas]

Replaced the o2 sensor, cleared faults, did a reset of adaptations, fault hasn't come back, and now lambda seems to be working fine, fluctuating at idle on closed loop between 0.3 and 0.8.

New o2 sensor heater resistance is exactly 6 ohms, old was 9-10 ohms, so it seems that the heater resistance must not exceed 6 ohms by much.

Bought the new o2 sensor from amazon for 70 euros, for anyone interested the part number is NGK 0074, or OZA630-BM3 .

[WayneC]

Pleased to hear you have the problem resolved, yes I was aware of the part No, sticking to the 6 ohm NGK rather than the Bosch is better