Sensor Only Works on Fast Heat

[Dubai944]

Hi,

I have an M400 with onboard Lambda.

I just replaced a 3 year old NGK sensor which had stopped reading and showed continual C6 error. I installed a new LSU 4.2 sensor, configured it and did a free air calibration successfully with fast heat selected. I then switched it back to normal but it immediately showed a C6 error and gives no reading even after starting and running the car up to temps for 10 minutes and more. As soon as I switch it back to fast heat it works fine and reads normally.

I have double checked all the wiring and setup settings according to the MoTeC LSU 4.2 guide and everything seem to be correct. What to check next?

[Scott@FP]

http://www.motec.com/forum/viewtopic.php?f=11&t=738&p=6107

Might answer a couple of your concerns.


Forum search is somewhat broken, if you search for "Lambda error C6" search returns nothing because all the terms are considered 'too common'.

[Dubai944]

Thanks, I did read that post previously.

From it I can only get that a C6 error indicates the ECU can't control the sensor and shuts it down, but the reasons given are either poor wiring, bad sensor or carbon on the sensor. In my case the sensor is new and works perfectly well with fast heat selected, so none of those issues appear to be the reason.

The other reason given is that on normal heat a C6 error will show while the engine is not running or while it is heating up, but in my case it doesn't matter how long I run the engine or the ET, if it is set as normal heat it continues to show a C6 error. As soon as I switch it to fast heat it works properly. Could a new sensor be faulty and only work in fast heat mode, or is this simply an indication that something isn't right in the ECU setup?

[Scott@FP]

Check the heater 12v and heater gnd (aux) wiring, at least 18g on the heater gnd, if OK try swapping it to another aux, inj, or ign to verify the currently used heater control circuit is OK, after that, I'm out of ideas.

I always thought the C6 error was 'operation suspended by ECU' due to a cut or TC being active, program is currently on a table that requires the La control to be open loop, or other logic reason, and not a fault condition. Hopefully someone can confirm what the C6 error is. But your being OK on fast heat but not normal heat points to a sensor heater circuit issue, or the sensor is just not getting enough heat into it from the exhaust stream to operate properly on normal heat.