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        General >> Give/Need advice to/from others >> PIN 55 ECU 12v always powered
        
(Message started by: szinyei on Sep 30^th, 2025, 11:20am)

Title: PIN 55 ECU 12v always powered
Post by szinyei on Sep 30^th, 2025, 11:20am

Hi there,

does somebody have an idea where the PIN55 wire is going? Actually it should provide steady 12 volts to the ECU in order that it retains the saved values from the sensors. But apparently it ends up on the wiring diagram in fuse nr. 37 which is definitively ignition switched.
Appreciate any help.
I want to bypass the whole system and make a switch to shut down the electric of the car. But at the same time I do not want to switch off the ECU. I would directly power it from the battery through a fuse of course…
I am playing because of the loom - I have a current drainage of around 0.1A…
The car is runnig „fine“ - it needs some more optimisation though…(therefore I am building an ignition switched current source - but that is another story…C663 green cables…PIN6…)

Best regards, Csaba

Title: Re: PIN 55 ECU 12v always powered
Post by Tompion on Oct 2^nd, 2025, 9:10pm

According to this page:
https://www.fordscorpio.co.uk/12vlooms.htm

With the ignition off, voltage is present at pin 1 of the PCM (A147) to protect the data stored in memory.

I assume you didn’t mean the 24V, that’s pin 55 going to fuse 31.

Dave

Title: Re: PIN 55 ECU 12v always powered
Post by szinyei on Oct 4^th, 2025, 8:11pm

Thank you Dave! I did not specify which engine I have. It is a 2.0 16v manual. I will measure the voltage directly on PIN 55 to make sure. I made a mistake: it not F37 but rather F31 10 Amps. I measured the voltage in the fuse box and it is definitely switched off with key removed. I keep you updated, but if you have further ideas, please feel free to let me know. thank you. regards, Csaba