Connector C90 Engine Fusebox - Beware!

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I read an old post on this forum about problems after removing the 41 pin connector C90 in the engine fusebox and I have just had a similar (highly stressful!) experience.

I will detail my experience here as a cautionary tale for others.

The car is a Focus 1.6Tdci mk2 and the problem started with an engine malfunction warning and limp mode.

When I got the car home I put the OBD reader on and ran up Forscan. The malfunction was down to error P0380 - glow plug malfunction. This DTC comes back as soon as you try and clear it.

Reading up on P0380, it seemed that the glow plugs themselves were the most likely cause. I did check the fuses in the engine fusebox, but they were OK.

Then I had a look at a wiring diagram for the glow plugs and saw that the wire from each glow plug comes back to the engine fusebox where they are all commoned.

So I got to thinking that by removing connector C90, I could then check each glow plug by checking its resistance to earth from the 4 relevant pins in C90. This would confirm that the glow plugs were faulty and also tell me which ones - maybe with the option of not changing those with diificult access if they were OK.

So it seemed like a good plan and the resistance checks showed that ALL the plugs were faulty!

I then put back connector C90 and my real troubles began. As soon as I tried to start the car I got Pats error 16 - fauly link from pats to ECM.

My first thought was that I'd zapped the ECM, as I had omitted to disconnect the battery before removing C90. I checked all the fuses in both boxes and they were OK. This was getting serious! Visions of an expensive trip by recovery vehicle to the Ford dealer!

Then I decided to have another look at C90. On close inspection, the socket pins in the connector looked like they weren't "closed up" enough to make good wiping contact with the male pins in the fusebox, so I took each pin out of the connector in turn and with a tiny screwdriver, bent the wiping contact outwards. Still no joy! Looking at the connector when inserted, it had clicked into place but the insertion did not seem very positive - too much play.

Then just on a hunch I decided to remove the red plastic insert that sits in the bottom of the connector. I don't think it does much other than aid insertion and keep the male pins straight.

I then reinserted the connector and straight away the insertion was positive and without play and sure enough the car was back up and running. Phew!

So my advice to all is to remove this connector at your peril!

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