1.6 hdi sensors

[Ferru1104]

Hi all, my 58 plate 1.6 hdi berlingo (VIN VF7**************[VIN obfuscated, can be read by forum staff]) has stopped working.
Since about a year the turbo stopped working so practically I was driving around in a 1.6D. Digging the forums I concluded that the pressure converter must have failed, so about a month ago I sourced one from the scrappy. Since the donor was a good looking car I took the MAF sensonr too, just in case I might need it. Installed both of them, and the turbo came back to life! I was so happy I even ignored the check engine light that appeared, atributing it to the newer MAF being I don't know, too new? The car drove great, I even recharged the ac which was working great too. The surprise came few days after when I stopped by a mate and the car refused to restart. After some cranking it did fire up but got only to the end of the street.
I don't have Lexia but the day after I got hold of a oldish diag tool and got these codes:

P0113 Intake air temperature too high
P0104 Intermittent MAF sensor signal
P0087 Common rail pressure too low
P0088 Common rail pressure too high

As first action I put back the old MAF sensor which was working fine, then cleaned the air temp sensor with carb cleaner, cleared all errors and tried to restart. Lo and behold it fired up instantly. After about three minutes idling I gave it some revs and it died again. So much for having solved the Problem. This time the codes were the following:

P0088 Common rail pressure too high
P0113 Intake air temperature too high
P0104 Intermittent MAF sensor signal
P0238 Turbocharger Boost Sensor A Circuit High
After that it would not start anymore.

I don't get it, how come all these sensors are going bozo at the same time? If rail pressure is low then ok, the pump needs to be checked and maybe replaced, painful as it may be. But also the MAF, which was working ok? And the air temp and air pressure too? Is there a point in the abyss of this engine where all these cables are bundled together and fail? Is there a fuse related to all of their functions?
Please help me out with this, the last thing I want to do is to bring it to a mechanic. I have heavy trust issues with them.

[RichardW]

Seems likely you have lost either the 5V reference or earth that seems to be common to these sensors. It might be one of the other sensors has shorted out and is pulling the signal down.

[Ferru1104]

Thanks for the reply. Any idea how I should proceed? I guess I could unplug one by one the sensors but then I'm sure the ecu will block the engine from starting.

[Ferru1104]

Solved.
Whoever runs into problems with multiple sensors going haywire, don't panic, only one of them is shorted.
Proceed like this. Disconnect battery, grab a multimeter, clamp on the earth wire a clip, set multimeter to continuity. Unplug your maf sensor, check all terminals. One of them should go beep, that's the earth. If none of them beeps, go to the next sensor, for example map sensor, camshaft position sensor, do the ones easy to reach.
Of none beeps, don't dismantle the engine looking for further plugs, but remove the front right wheel and a piece of trim covering your crankshaft pulley. Right next to it will be, most probably covered with oil/dirt/mud the crankshaft sensor. For me that was the bugger, it was shorted and messed up all the other signals' readings. Changed it and all was good.
Thanks to RichardW, you were right that earth was lost somewhere in the sensors.

[RichardW]

Glad you got it sorted, crank sensors on these don't often give trouble so you are unlucky!