AIT sensor reading -40.000

[Nutsbolts1234]

Hello, I am looking for help please. I have a 2011 Citroen C1 1.4 HDI VIN No VF7**************[VIN obfuscated, can be read by forum staff] with a Siemens SID805 ECU 5WS40691A-T. The AIT sensor is reading -40.000 degrees. I have so far changed the AIT sensor and the MAF before I checked any thing with a multimeter. There seems to be 5v and earth at the sensor and without removing the ECU itself I can see that the 5v and earth are present at the ECU connector (middle one) as when I disconnect it both 5v and earth are lost. This is as far as I have gone apart from reading the data stream which only identified the -40.000 reading. The symptoms I am trying to rectify is hard starting/rough running in the cold weather. Warmer weather is fine.
I have 4 fault codes registered
P0113
P1350
P1351
P0111
I would love it if someone could provide some guidance. Also if anyone confirms/suspects ECU fault, then the best place to send for test/repair.
On a side note I have also recently replaced the glow plugs and EGR valve in blind attempt to repair.
Thank you in advance.

[Nutsbolts1234]

Sense check please. Regarding the post attached, I have confirmed continuity from the 2 wire Air Intake Sensor to the ECU plug which should eliminate the wiring from sensor to ECU and also the AIT sensor as I tested it previously with a hot air gun and an ohmmeter.
The data stream still reads the AIT at -40.000 degrees so I am pretty sure now it’s the ECU at fault. Any thoughts?

[Nutsbolts1234]

Photos attached. Pins marked red are the ones that prove continuity from AIT to ECU.

[GiveMeABreak]

I can't really help you with this one as this engine is one of those collaborative Ford / Renault, Mazda / PSA Group projects. I don't have the specifics on this engine ECU, but somebody else may. It's basically a Toyota Aygo, but the engine is as described, so I don't have a lot of info on it.

But the vehicle is being flagged up for an outstanding recall - so I suggest you call the dealer, quote the VIN and they'll be able to tell you what it's for, but will be free for the work involved. You never know, it may even be related to the current issue...

The P1350 (Relay) & P1351 (plugs) codes are related to the glow plugs and the Glow Plug Relay.

P0113 is: Inlet air temperature at the air flow sensor: Voltage of the component too high.
P0111 is: The IAT sensor range input to the ECM went to -40°F or 240°F indicating a short or open circuit.
The IAT sensor input to the ECM is erratic and not giving a steady stable reading.

[wheeler]

If you measure the resistance across pins A2 & D3 of that brown ECU connector (with the ECU disconnected but the AIT sensor plugged in) then warm up the sensor with a hairdryer does the resistance reading drop then go back up when it cools again?

[GiveMeABreak]

Also, watch for parts quality - if you got the sensor from ECP, don't be surprised if it's faulty.

[Nutsbolts1234]

Hello, sensor was a Lucas part not ECP and I tested it previously with a hairdryer and it was ok by back probing it. As I have now confirmed continuity of those wires back to the ECU plug also it seems logical that that circuit is ok.
Recall - interesting, I will contact the dealer thank you.
Richard

[Nutsbolts1234]

So, after replacing the ECU with a second hand unit (cloned by a friend) the air temperature sensor is now registering in the ECU. Whilst this cured one issue, another issue became apparent now that the main one was resolved. The lack of power and knocking under load turned out to be two faulty injectors. Sent all four to Colchester Diesel Injection which ended up with me buying and installing two reconditioned injectors supplied by them. All good now.