ECU fuse

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Discussion

Petemate

Original Poster:

1,674 posts

198 months

Thursday 22nd November 2018
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Had a problem with our Saab 1.9 tid 9-3 the other day. Problem was caused by a short circuit in the diesel fuel filter water sensor, this blew the 10 amp F4 ECU fuse. Happily the car was on the drive, and not on the road. A friend also with a Saab 1.9 tid had exactly the same symptoms (though not AFAIK his water sensor) a few years ago, and worryingly for him, his car failed on a motorway and he was able to get over to the hard shoulder but the power steering had also failed as well as the engine cutting out completely.

I am wondering how many other cars could potentially fail in this way? Doesn't do well for confidence in modern automobiles!! My OH frequently is out in the car on her own and I would not like for this to happen to her, especially considering that the power steering failure would probably take her by surprise knowing the superhuman effort required to operate it without the power element.

Granted that in a perfect world there should not be a short circuit in a car's wiring that would cause the vital fuse to blow - but - sods' and murphy's law and all that, eh peeps?

After a bit of thought on this, I think that if the ECU on a vehicle shares its fuse with other services, eg in the case of the Saab 9-3 tid the power steering, MAF and water sensor, then really those items other than the ECU ought to have lower rate fuses fitted in their wiring to ensure that the car continues to be able to be driven to a place of safety. Then, I suppose manufacturers would not be willing to spend a bit more on their products. We can't win.

Edited by Petemate on Sunday 25th November 09:27

MajorMantra

1,491 posts

119 months

Wednesday 5th December 2018
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Traditional hydraulic power steering relies on the engine to drive its pump. That's why you lose assistance if the engine cuts out. It's got nothing to do with fuses.

giblet

8,932 posts

184 months

Sunday 26th February 2023
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Sorry to bump an old thread but did replacing the sensor stop the fuse from blowing again?

I ask as I had the same warning come on recently on a long drive. A few days later the car refused to start. Despite replacing the fuse a few times it would just blow it every time I went to start it. My 9-3 has some aftermarket wiring put in my a previous owner for bits like a powered rear aerial, rear camera etc. Removing some of the additional wires resulted in the car starting up but a day later it blew the same fuse

giblet

8,932 posts

184 months

Tuesday 28th February 2023
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Answered my own question hopefully. My water in fuel sensor was in a bad way, the wires were exposed and shorting out causing the same fuse to blow.

It’s been replaced and seems to be alright so far. Next job to tackle is all the extra wiring in the car and the aftermarket stereo which isn’t powering up anymore