Frustrating issue with DS3 stuck in open loop fuelling

[scott3823]

Good morning all, I am new to this forum and was hoping someone could help with a very frustrating fuelling issue in a 2011 Citroen DS3 1.6 turbo (same THP engine as in the Mini R53).
For a while now the fuelling system in my car has been stuck in open loop due to insufficient temperature, this is in spite of the coolant temp being normal (90 degrees) during normal running. I have:
Replaced both O2 sensors, and both seem to be returning valid voltages and can be read normally (both bosch parts)
Replaced the coolant temp sensor that is housed in the thermostat housing
Replaced the thermostat housing due to a leak
Replaced both intake sensors, MAP and turbo pressure sensors
The thermostat housing I have is now electrically controlled as early cars used 2 wire wax thermostats, then moved to 3 wire wax thermostats then to 3 wire electrically controlled. The car will cool down at times when driving and does take a while to heat up so I suspect something is happening with the thermostat, there was a recall for this engine that was carried out a few years back where I believe the thermostat changes were made.

I am kinda at a bit of a loss and don't know where to go next without dropping it with a blank cheque to a dealers. This issue is causing big issues getting it through MOT's. I have the full DIagbox suite for this car so can carry out all dealer level functions/resets/checks etc.

Any help appreciated. Thanks

[E-bmw]

You say it is in open loop due to insufficient temperature, where is the "insufficient temperature" being reported?

Surely that is where you need to be looking?

[scott3823]

The insufficient temperature isn't being reported, there are no more temp sensors I could find that would be reporting a low temp (I don't think these engines have a oil temp sensor).

[E-bmw]

So how do you know it is being held in open loop due to insufficient temperature then?

[scott3823]

2 different ODB2 apps on Android and the complete Citroen Diagnostics setup (diagbox) have reported this condition for many months. Also difficulty getting the car through emissions tests.

[GreenV8S]

Emissions tests are done stationary, which eliminates many of the common reasons for overcooling. Without a temperature reading I think it would be quite difficult for you to know that your emissions test problems are purely due to overcooling. For example it's possible that running in open loop has poisoned that cat or that it's stuck in open loop because of some other problem which is also affecting emissions.

[scott3823]

Thanks for the responses. I knew there was a good chance the overcooling isn't related, but as they are both temperature related it could be.
I am certain that the open loop issue is causing the car to run it's standard fuel map and not use the O2 sensors to adjust the fuelling so I want to get it sorted either way so any suggestions as to sensors that could be causing the error or other things to change I haven't already thought of would be much appreciated.

[E-bmw]

scott3823 said:

2 different ODB2 apps on Android and the complete Citroen Diagnostics setup (diagbox) have reported this condition for many months. Also difficulty getting the car through emissions tests.

You still aren't answering the actual question.

What/how/why/where/by what means are you getting the information that the engine isn't up to temperature?

[scott3823]

I'm sorry but i am answering the question. So to reiterate the engine IS GETTNG UP TO TEMPERATURE, however the car never enters closed loop fuelling, this is verified with on board diagnostics that report open loop due to low temperature. This is a permanent state, and this is what i am trying to troubleshoot as the car should go to closed loop when warm.

[Dave.]

The sensor which reports the temperature is a possible culprit, you need to find which sensor is (mis)reporting the temperature to the ecu.

Edited by Dave. on Monday 6th December 20:11

[E-bmw]

scott3823 said:

I'm sorry but i am answering the question. So to reiterate the engine IS GETTNG UP TO TEMPERATURE, however the car never enters closed loop fuelling, this is verified with on board diagnostics that report open loop due to low temperature. This is a permanent state, and this is what i am trying to troubleshoot as the car should go to closed loop when warm.

So if the engine is getting up to temperature why are you saying the car is in open loop control because of insufficient temperature?

Can you see why I say you are not answering the question?

[scott3823]

Dave, thanks for the response, I suspected that would be the case. The only temp sensor I can find it the coolant temp sensor, which is reading OK and has been replaced just in case. Does anyone know of other sensors that the ECU would use to gauge the temperature that the driver wouldn't normally see?

[Penelope Stopit]

I know zilch about your engine and its diagnostics

But

Is there a possibility that the ECU is calculating hot engine coolant against O2 sensor output voltages that point to an engine being cool?

If so

Faulty/incorrect O2 sensors or faulty sensor circuits could possibly be causing the problem

scott3823 said:

Replaced both O2 sensors, and both seem to be returning valid voltages and can be read normally (both bosch parts)

Do you know for sure what the above voltages should be when the engine coolant is hot?

Just a thought

[scott3823]

I certainly cannot rule out something faulty in the O2 sensor curcuit, but think a garage might have to be the ones to confirm that sadly as I have already replaced the sensors.
SO here is a screengrab of the diagnostics. The coolant temp is correct, tallies with the gauge and the radiator fans are triggering. I would say the intake temp is pretty accurate for the outside temperature today. Yet as you can see the fuel status stays stuck in open loop.
The O2 sensor voltages seem OK, they tend to sit at about .8 volts which would suggest running too rich (which would correspond to the emissions failures), however the voltages do drop when lifting off throttle which would tally to the injection cutting the fuel and running lean.

[GreenV8S]

Penelope Stopit said:

Is there a possibility that the ECU is calculating hot engine coolant against O2 sensor output voltages that point to an engine being cool?

No. Engine temperature cannot be inferred from the lambda sensor output.

[GreenV8S]

scott3823 said:

they tend to sit at about .8 volts which would suggest running too rich

Do you know what type of sensor it uses? Zirconia is most widely used, but Titiania sensor have very different electrical characteristics.

ETA: Zirconia sensors only work when hot and the fault code may be trying to tell you the sensor isn't hot enough, perhaps because the heater / heater circuit have failed. But you seem to be getting at least some reading from it, which tends to suggest it's working to some extent.

Edited by GreenV8S on Tuesday 7th December 16:33

[E-bmw]

Not sure if it true of your sensors or not but I had an issue several years ago on an early 90's BM, those sensors had heaters for getting up to temperature & these were put on be a relay, one of these had failed causing the sensor not to get up to temperature.

It just may be worth a look at the wiring diagram for them.

[scott3823]

Cheers for your help everyone. In Diagbox i am able to see the status of the O2 sensors heaters so i will have a look at this tomorrow and post back my findings.

[shalmaneser]

E-bmw said:

Not sure if it true of your sensors or not but I had an issue several years ago on an early 90's BM, those sensors had heaters for getting up to temperature & these were put on be a relay, one of these had failed causing the sensor not to get up to temperature.

It just may be worth a look at the wiring diagram for them.

I would look into this also, most lambda sensors have built in heaters. Given that OP has replaced sensors however could something be fried further upstream of the lambda connector that means power isn't getting to the lambda heaters?



EDIT: likely this is high current so might well be fused...

[Penelope Stopit]

GreenV8S said:

Penelope Stopit said:

Is there a possibility that the ECU is calculating hot engine coolant against O2 sensor output voltages that point to an engine being cool?

No. Engine temperature cannot be inferred from the lambda sensor output.

Where did I mention engine temperature?