I've got a 2010 2.0 TDCI focus with the keyless entry and start, a few days ago for some unknown reason the car battery died, needed the car the next day so removed the battery, charged it overnight, put it on the next morning, drove it about 30 miles, left it parked up for a few hours, drove it back with no issues.

Went to use the car a few days later and it was totally dead again, charged the battery for the next couple of days, went to use the car but it seems it's not recognizing the key fob, had to unlock the door with the key which set off the alarm, none of the buttons on the fob work with the car, I've not tried the fob battery yet but I changed it not that long ago and have not had any low battery warnings.

Charged battery again and reconnected it to the car, everything seemed ok but when I turned the car on after a couple of seconds I'm getting a "Transmission Malfunction" message and the car won't start. I've bought and fitted a new battery expecting it to sort it out but exactly the same, I've looked on here and the web but can't find a solution.

Anyone have any ideas?

 

I've plugged in my obd reader which had previously worked on my car but it's showing some codes and then saying "communication error", codes are pwm, vpw, can, kwp iso, kwp5bps and kwpaddr. I think the 3 letter ones are to do with the reader trying to connect to the car.

 

Not on a focus, but before i had a car that wouldn't start i tried a decent diagnostic tester on and it said the same thing - cannot connect to ecu or something similar. Turned out to be no earth to the engine ecu, hence the car not starting or tester not working. Ran a new cable from battery to chassis to ecu. Everything worked fine again.
but before that i did the same as you, changed battery etc to no avail.

 

These are all different methods of communicating under the EOBD/OBD2 regulations.
The "kwp .." ones were used before there was can. As of 2008 can is the only allowed protocol.
The reason for the message "Transmission failure" and the non-communication problem could also be a defective can-bus.

 

I can't get the diagnostic reader to work at all, I've checked all fuses and tried disconnecting every sensor under the bonnet that I can see but also the instrument cluster and still nothing, car won't even attempt to start, stressing me right out now, what else could it be? I've tried looking for an oxygen/lambda sensor on the exhaust or near the cat but there doesn't seem to be one.

New battery, earth going to body is fine and earth going to alternator is fine.

I am getting "Engine Malfunction" as well as the "Transmission Malfunction" messages.

 

I just tried swapping the clock cluster from my mothers Focus but still showing fault.

 

A diesel does NOT have an Oxygen sensor in the exhaust manifold.
If it has an Oxygen sensor it will be behind the DPF.

The reason for the the message "Engine Malfunction" is probably because you disconnected sensors.

Your car uses the can-protocol.
Can you measure the resistance between pins 6 and 14 of the diagnostic connector with the key turned off.

 

I've measured between those pins and it's showing 120.6 ohms, is this normal or too high?

 

Swapping the dash cluster won't work as they are coded to the ECU. Have you checked the ECU earth? I have seen before these corroding and giving all sorts of problems.

 

Where can I find the ECU earth?

 

How do you actually open up the ECU? Looks rivited rather than screws.

 

They look like tamperproof screws, get a dremmel or similar and cut a slot in them or drill the head off is poss.

 

Not too worried about getting them off, it's wether it would go back on then.

 

If you can get a small dremel type tool in there to cut a flat slot can use a flat screw driver, just fit some new screws as long as they're nothing special for length etc.

 

Right I've given up and gave the car to a mechanic, looks like the passenger footwell fusebox is water damaged, does anyone know how if they are all the same or do I need a specific one, ie does it have to be for my 2.0 diesel, is it keyless specific...?

 

This is the corrosion in the fusebox, I've cleaned it up using IPA, has anyone done this successfully and found the car is ok after or will it have damaged something?