Hi all,

I'm trying to track down some weird ECU or sensor behaviour in my 2011 XF-R. I first noticed that when adding the custom PIDs for IAT2 in Torque that the IAT2 temperature was insane (100+ °C after a 20 minute drive). Initially I panicked thinking my chargecooler pump had failed, but it appears to be fine. The real symptom is that all 3 IAT sensors - the 2 MAF sensors in the intakes and the IAT2/MAPT sensor in the left inlet manifold - are reporting crazy values. For example, this morning I did some SDD datalogging before starting the car to go to work. It had been sat on my drive for 12hrs+ without being driven. The ambient air temp sensor in the wing mirror was reporting 14 °C which is pretty accurate, it had obviously been colder overnight. Before even starting the engine Air intake temp bank 1 was reading 26 °C and bank 2 was reading 30 °C! IAT2 was showing 26 ° C also.

There are no stored DTCs, no 'restricted performance'. The temperatures do rise with the engine running, to unbelievable levels. All 3 sensors misbehave in the same way. I've also discovered again through SDD datalogging that if I unplug the bank 2 MAF SDD reports the temp as -40. If I unplug the bank1 MAF the intake temp doesn't change as though the PCM/ECU is ignoring the value of the sensor. Swapping the MAFs makes no difference, as I would expect if crazy made-up temperatures are reported even with the sensor unplugged.

Ambient temp remains accurate. I've seen some stuff like this in the workshop manual: "If the NTC thermistor signal fails the ECM adopts a default value of 25 °C (77 °F) for the intake air temperature." that's only 1 degree (rounding up?) away from what I'm seeing on at least 2 of my sensors. I'd expect a DTC if the ECU was having to do this though.

Cleaning the MAF sensors has made no obvious difference. I am leaning toward this being an ECU fault but I'd welcome any input!

 

The actual figures I pulled out of SDD:

From cold (engine off for 12+hrs). Engine not started at this point, but ignition in position 2

SDD
Air intake temp (PCM) 26 deg C
Ambient air temp (PCM) 14 deg C (actually correct)
Ambient air temp voltage 2.05V
Intake air temp bank 2 (PCM) 30 deg C
Intake air temp sensor voltage (PCM) 1.89V
Intake air temp sensor voltage bank 2 (PCM) 1.85V
Intercooler outlet air temp Bank 1 (PCM) 26 deg C

After running for 10 minutes:
SDD
Air intake temp (PCM) 39 deg C
Ambient air temp (PCM) 16 deg C
Ambient air temp voltage 1.94V
Intake air temp bank 2 (PCM) 21 deg C
Intake air temp sensor voltage (PCM) 2.32V
Intake air temp sensor voltage bank 2 (PCM) 2.26V
Intercooler outlet air temp Bank 1 (PCM) 41 deg C