P0096 DTC

[KevinR]

Hopefully someone will know the answer to what is causing a P0096 DTC on my Micra.
Car : 2017 Micra 1.5 dci
P0096 DTC code : "Intake air temperature (IAT) sensor 2 -circuit range/performance"
This really translates into the temperature that the IAT2 sensor is reporting to the ECU is not coherent with the temperature that the IAT sensor is reporting to the ECU.

The car has just been serviced (not by a main dealer), but the fault has not been cleared.
The car has had a new Airfilter, and a replacement MAF/IAT sensor, but no change.

Using Autodoctor Professional 7.0.1 for IOS, I believe that I've identified the likely cause of the P0096 code, but I'm now at a loss as to how to cure it.
The IAT2 temperature sensor reading is NOT reported by Autodoctor, but the IAT temperature is reported, and is wildly on the high side.

To eliminating any issues with heat soak, the car has been sat in my garage for 2 days, so the engine and all components are at ambient tempeature.

The Air Temperature sensor reports 20degree C (yes, its 20, and that is also what is displayed on the dash)
The IAT sensor that is combined with the MAF is reporting 55 degrees C - so about 35 degrees higher than it should be for a cold engine.
Assuming that IAT2 is reporting a reasonable temperature (circa 20 degrees) the massibe difference between IAT and IAT2 is causing the P0096 DTC.

Refitting the orignial MAF/IAT sensor gives the same reading, i.e. 55 degrees C.
Running the engine causes the reported temperature to rise slightly, and after a bit of heat soak, it hits about 60 degrees.

Disconnecting the MAF/IAT sensor gives P0113 - which indicates that the IAT sensor is open circuit.
This code clears as soon as the sensor is reconnected.
Cooling the IAT sensor with freezer spray does NOT reduce the reading by any significant amount.

I've reseated all the connectors between the sensor and the ECU and still no change.
I've disconnected that battery and left it disconnected for an hour and still no change.

Checking the behaviour of the same set of sensors on a Qashquai 1.5dci of a similar age gives a set of readings that are realastic, with an IAT of near ambient air temperature.

So the real question is, what is causing the IAT sensor to report such a high air temperature ?

Thanks in advance for any disagnostic suggestions.

 

[FinnishCoffee]

I'd assume the intake air temperature reading being that high (55 C) is the root cause of your problem. While I could not find a K14 service manual, the K13 intake air temperature sensor seems to be a NTC thermistor, meaning the resistance will decrease as the temperature rises.

In this case, a wiring fault would cause an incorrect reading. As you are able to read the value coming for the sensor, I'd recommend trying to heat the sensor with i.e a hair dryer to see if it is reacting to temperature.

Regardless, I'd inspect wiring and especially any connections between the sensor and the ECU for signs of physical damage or moisture.

 

[KevinR]

I'd assume the intake air temperature reading being that high (55 C) is the root cause of your problem. While I could not find a K14 service manual, the K13 intake air temperature sensor seems to be a NTC thermistor, meaning the resistance will decrease as the temperature rises.

In this case, a wiring fault would cause an incorrect reading. As you are able to read the value coming for the sensor, I'd recommend trying to heat the sensor with i.e a hair dryer to see if it is reacting to temperature.

Regardless, I'd inspect wiring and especially any connections between the sensor and the ECU for signs of physical damage or moisture.

Many thanks for the ideas.
I too suspect that the high IAT is the cause of the P0096 DTC, but I'm struggling to work out why the reported temperature is so high.

I've inspected the connectors at the MAF/IAT and they are clean, with no sign of contact corrosion.
Likewise I've inspected the wiring and connectors going into the ECU and again they are clean with no sign of contact corrosion.

I'm unable to locate any intermediate connectors between the MAF/IAT and the ECU, and as I don't have a wiring diagram, I cannot be sure that there aren't any (but they are very close together so I've no reason to suspect that there is an intermediate connector.

There is no sign of water ingress and no sign of damage.

Heating the MAF/IAT with a hair dryer does NOT cause a change in the reported temperature, which I'm finding suspicious.

The sensor is one of these https://www.b-parts.com/auto-parts/...-15-dci-rsa226807131r-gm93450753-2016-5965318

I've got the original one from the car, plus 2 new ones and I get the same behavior from all three of them.

Does anyone have the relevant section of the wiring diagram, the pinouts of the sensor and a temperature/resistance curve for it ?

 

[KevinR]

I downloaded the K14 Nissan Workshop Manual from Easymanuals.co.uk and it was no help what so ever,
Despite being over 4000 pages of a PDF file, the critical "EC" section was not included - I've emailed them to request the missing section.

I do however think I'm narrowing down the problem.
The IAT1 sensor is the same as the one on my Qashqai - and I have the complete manual for that, including the EC section.

The temperature curve data in the QQ manual confirms that all three MAF/IAT sensors I have are all giving a good temperature response.
I then checked the resistance between the IAT1 sensor and the ECU - had to find the pins by trial and error as the K13 ECU pinouts are not the same as the QQ ECU pinouts.
The resistance between the ECU pins and the IAT1 sensor are fine, and checking the temperature response curve at the ECU connector again confirms a correct response from the IAT1 sensor (both for ambient, and with heating using a hairdryer)

Therefore it MUST be the ECU itself that has the problem.

Are there any known reliability problems with Nissan ECUs ?
For example, is it possible that there is an internal dry joint in the ECU ?

Has anyone opened up an ECU, does it open easily (I'm an Electronics Engineer, so I have all the equipment I need to prevent Electrostatic damage, and if necessary resolder a dry joint)

Does anyone have any photos of an open ECU ?

Alternatively, can the ECU be remapped to change the way it interprets the sensor resistance ?
Or is there a simple way to fully reset an ECU ?

 

[York of shire]

As far as I’m aware the iat sensor 2 is built in with the downstream boost sensor which sits just under the low pressure egr. That would be my suspect for the failure.