EV + ACC system service required - rear motor or control unit faulty?

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Bagpuss

Member
Joined
Jan 1, 2015
Messages
11
Location
Netherlands
Hi,

My 2014 PHEV has started coming up with "EV system service required" and "ACC system service required" messages.

The errors will appear either when starting the car, or on a journey, or - very occasionally - not at all. Once the messages appear, the car will no longer drive with the engine, only on electric (the motor can be fired up but it doesn't seem to actually use it and it stops again a bit later). Acceleration is much reduced. If the message appears while driving, you can hear a 'bonking' noise coming from the back of the car.

The exact same problem happened exactly a year ago. I took it to the dealer and they had it for half an hour, reset some stuff, and gave it back. They didn't charge me for it and it has been fine ever since. Now the car is back at the same garage and they tell me that Mitsubishi's guidelines say that the rear motor is at fault, but the mechanic has tested it and has a feeling that it is actually the control unit. The motor can be replaced with one from the scrapyard, but the RMCU is one-time programmable and has to be bought new. Because he is not sure exactly what is at fault, he's leaving it up to me to decide which way to go :? Obviously I am alright with paying for a job to be done if the problem is fixed (though given the age and mileage of the car I still will be wanting to ask Mitsubishi for a contribution), but I won't be happy to pay to replace a major part only to discover that it hasn't helped.

Anyone got any ideas of what I can do?

Thanks,
Dave
 
That's a joke. They should be able to diagnose what component is at fault, not just guess at parts and replace them. They should find out exactly what is triggering the fault, it has to be a sensor, and from there use a fault tree analysis to further diagnose the issue and get to the root cause. I would not be prepared to pay for any other process.

There is anecdotal evidence that mismatched tyres can cause this, are all of yours even wear and the same brand and model?
 
Yes I had checked the tyres beforehand, they are all the same type and were installed at the same time, and the wear is not drastically different across them.
 
Bagpuss said:
My 2014 PHEV has started coming up with "EV system service required" and "ACC system service required" messages.

You don't have an OBD adapter connected by any chance do you? These have been known to throw EV Service faults.
 
Hi!
I have the same problem.
The car stops ECU and show errors EV and ACC. If restart car immediatly it fails again.
I checked error codes, there is only few FCM errors.
What i fount is that if you stay some with open hood - it restores and drive normally some range.
 
No, but I did use one once the problems started again to confirm that it was the same set of error codes as the garage found last year.
 
You need to take it to a different dealer but, also what happens when the battery is "empty"?
 
I haven't actually tried to run the car until the battery was empty. It might be that running it in charge mode might have helped keep the battery topped up.

The dealer in question is pretty much the only Mitsubishi garage in my province. I even called up the garage I bought it from back in 2014 to see if they could help, but they are no longer a Mitsubishi garage, have no contact with them any more, and tell me that the car 'is in the right place'. We'll see about that :D

The latest news is that they have sourced a second hand rear motor and will try to fit it, but I have told them that I'm not going to pay for it if it doesn't fix the problem. They say that they are still in communication with Mitsubishi about it, because their flowchart points solely to the motor being the issue. They are going to lend me a car for free while it is there, so that is at least something.

Frustratingly I was considering part-exchanging the car earlier in the year, but decided to leave it until next year. That decision is going to bite me in the bum now :D
 
I would have thought that getting noises whilst in motion does suggest a mechanical problem but, of course, an electronic fault could be causing that.

However, I don't understand why you would need a brand new control unit rather than that also being second hand - what is it they claim to be uniquely programmed to a particular car :?
 
After a phone call on Friday, the latest is that they have confirmed that it is the control unit.

They have quoted me €2750 for a new part and €350 to fit it - and it is on back-order until at least September.

They also say that they can try fitting a second hand unit and try to reprogram it. I will go and talk to them in person on Monday to try and work out why they initially said it was 'one-time programmable' yet now they claim that it is possibly reprogrammable. They did say that they had never done it before, and I don't mind them trying it out as long as it doesn't delay the fitting of a brand new part if it doesn't work out. A possible downside to going down the second-hand route is that it will shut the door to asking Mitsubishi to chip in, because they will only do that when replacing stuff for new parts.
 
Hallo Bagpuss I have exactly the same problem with my 2014 phev. Did replacing of the control-unit solve the problem? Regards Aat
 
Hallo Bagpuss I have exactly the same problem with my 2014 phev. Did replacing of the control-unit solve the problem? Regards Aat
Sorry, I didn't receive a notification of your reply and have even since sold the car.

For anyone reading this in future: yes, replacing the control unit did fix the problem. The new unit took 2-3 months to arrive from Japan. Mitsubishi paid 10% of the cost of the part, so my total cost including fitting was €2800.
 
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