Hi

Has anyone tried resetting the ECU on a Mondeo? I have a 2.0 TDCI GHIA X (automatic) 2003 with a speedo not working and seatbelt warning light/alarm not working. With 2 batteries in parallel the speedo works (I´ve recently put a new battery in 70Ah). I took it to my local mechanic and he´s never seen this before. Things are pointing at a faulty ECU so wanted to try resetting it before looking for a replacement.

Any ideas?

Cheers

Gary

 

This looks far more like either a BCM (Body Control Module) or IC (Instrument Cluster) fault, not the ECU.

Does the car start and run as normal ?

Car usually starts ok. Sometimes it takes 3 goes (always 3!) but runs fine once fired up. The really odd thing is the 2 batteries in parallel. I drove it (on my driveway, about 15m) with 2 in parallel, ie the new on, which I´d charged full overnight, and the one I´d replaced, and the needle on the speedo moved.

A friend suggested it might be the earth strap connection. I put a jump lead on the neg, then to the body. No change.

If your new battery is fully charged and the alternator is working fine I can offer no reason why 2 batteries in parallel would make any difference.

Was everything working fine before you fitted the new battery?

NO. I put the new battery in because I´d read about someone having exactly the same problem and they discovered they had a faulty cell in their battery. Changing the battery solved it for them ..... but not for me!!

Now that makes a lot more sense.

Ok so you need to use the software called 'ForScan' (its free) download it on to a laptop.   https://forscan.org/home.html

You will also need a good ELM327 lead to connect your laptop to the OBDII port. Use something like the one from Tunnelrat Electronics (£17.99)  

https://tunnelrat-electronics.fwscart.com/USB_Modified_with_switch_ELM327/p4541936_17045457.aspx

OR

https://www.ebay.co.uk/itm/333939875124?hash=item4dc05e1d34:g:jp0AAOSwWixgUSh8

Then you can read the DTC's which will point you in the direction of the fault.

It could be that water has got in to the connectors of the BCM and has corroded some of the pins, or it might be the solder joints on the back of the IC are starting to fail. It might be something else so please don't just guess, use ForScan and find out what the real problem is.

X2 above, also, remove the battery and battery tray and inspect the earth connections  underneath. If looking rusty or corroded undo the bolts and clean up the surfaces. Check the bolts for tightness anyway.