"EV System Service Required" after problems with the aux battery

[Daixiwen]

So I started my car one morning, and had a bunch of "service required" messages coming up. EV system, ABS, FCM, ACC and a bunch of other stuff. Knowing the drill I went out and measure the voltage of the aux battery and yup.... 11.2 V
I connected the car to a 12V battery charger during the day and got a lift to work. During the evening I went back into the car and it started fine, without any errors. I was happy. It started like that 3 times, and on the 4th I got "EV system service required".
Thinking the aux battery was perhaps still a bit low, I kept it on the charger during the night, and the next day, even with 12.6V, still the same error message. The car won't drive, I don't hear the vacuum pump or the cooling pump when I start it, and it won't engage in D (just beep-beep).
I connected a generic ODB scanner and it found a few old archived codes (Heater System Failure, Hydraulic Clutch Actuator Valve Signal Fault, P1A1B and B1115). After clearing them they didn't come back, but I still couldn't drive the car. My ODB scanner didn't report any other code.

I had it towed to the workshop and they said they got codes from just each and every component connected to the high voltage system in the car. I hope that it was because of the low 12V battery? After clearing them there is one that comes back up immediately, the high voltage contactor. They managed to move the car but say it is not drivable now (I assume it's in turtle mode?) and that the contactor needs to be replaced. Apparently the issue is completely unrelated to the aux battery problem but I find it strange that both happened so close together.

Anyway they are sending a request to Mitsubishi to see if this can be covered by the 8 year battery warranty.... My car is 7.5 years old.
Did this happen to anyone else and did you get it fixed under warranty?

 

[kenny256]

i would suggest that it is indeed related to the aux battery. An old, weak or worn out aux battery will cause a multitude of faults in an EV. What power source do you suppose is used to hold the main contactors in their closed position?

What do you suppose happens if the main contactor gets interrupted by a loss of 12V power while it is under HV load? It causes a big spark and plasma arc inside the contactor, which can weld or damage the precious metal surfaces of the contacts, rendering them useless.

At 11.2 VDC your aux battery was way into the dead zone; charging it may have given the appearance of recovery, but the internal sulfation damage and loss of capacity was already over the edge.

Hopefully the contactor is easy to access and replace in the pack.

 

[Daixiwen]

It makes sense in theory but the only point when the aux voltage is low is when you start the car. After that the DC/DC is on so you have at least 14V on the line. When you start the car the current going through the contactor is not that high because nothing is on yet. They may be some in-rush current to load some capacitors but it's still low compared to the kind of loads you'll find when the car is driving. So I don't know....
Apparently it is a rather complex operation because the contactor is in the battery pack itself. According to the workshop it requires special tools, equipment and qualified personnel. We'll see!
I have changed the aux battery. It was as old as the car so it was time I think.

 

[kenny256]

You probably got all your money's worth out of that old aux battery, and unfortunately trying to squeeze that last little bit was costly.

There are large value capacitors in the inverter and charger that have to absorb about 14A in-rush current on the HV side; i can't recall measuring the 12V inrush currents but that would be a good todo item.

In theory the DCDC will come on, if the 12V does not have too high of impedance such that it can't sink any current (sulfated plates), and if the 12V level can hold up long enough to power all the relays and main contactors and motors in pumps and the multitude of 3.3, 5 and15V supplies in all the ECUs and boards, such as the DCDC board, where HV comes in at the upper left and 12V to the Aux leaves at the bottom right. 12V for LV supplies comes in at the bottom left connector and is not directly connected to the Output.

 

[Daixiwen]

I got some news from the workshop, they say now that it's not the contactor but the fuse inside the battery that was blown. They are going to change the fuse and see if they can find the cause.
Mitsubishi said that they will cover this under warranty only if there is a short detected inside the battery pack itself. If the cause it outside the battery it won't be covered.
It didn't happen while I was driving so it either went all by itself while the car was off, or (more probably) when I turned it on, which could be caused by a short in the DC/DC converter or one of the inverters. Or it just went off for no reason and everything will be fine after they change it. I don't like any of these cases, and especially the latter because if we don't find the cause I'll always wonder if it will blow again one day....

 

[kenny256]

They should have known this from looking at the data items list when using the MUT. It will show the condition of the main contactors as well.

When the key was switched to START then the main contactors would engage but there would be no HV output to the motor drive inverter. This condition would raise a DTC that should be easily read with the MUT also. Or any scan tool that can talk Mitsubishi protocol over the OBDII port.

 

[Daixiwen]

I don't have all the details, but now they changed the fuse and still get weird error codes from the MUT and none of the procedures from the technical manual can solve them. They have been talking to a Mitsubishi technical center to try and solve the issue but it looks like it will take some time. With my luck they will need a replacement part that is back ordered and not available before 2025

 

[Daixiwen]

They found out that there is a short in the PHEV ECU and it needs to be changed. It looks like we can only put a new one in, because the key code for the anti-theft system can only be flashed once. Of course there aren't any in stock around here and it needs to be ordered.
This is going to be my most expensive 12 V battery change by far!
I still wonder how this short could have happened though.

 

[kenny256]

So the good news is that there was nothing wrong with your HV battery pack? The contactors were okay and the fuse was intact?

i've repaired numerous ECUs and found that severe circuit board damage would occur if the ground terminal at the starter battery was loose, vibrated off or was removed while the car was running, or if the polarity was reversed. When the return path of an active circuit is interrupted, then a "new" path will be created for you.

Components that can fail "shorted" include cracked ceramic capacitors and melted semiconductor junctions (diodes, transistors). Most parts fail "open" when they blow or get blown off the board. The HV snubber capacitors in the OBC explode and spray hot molten metal inside that causes secondary failures. The PHEV-ECU doesn't have any high voltage or high current circuits so it may not show in a visual exam.

Request to get the damaged parts back from the service dept. Mitsubishi may want the old parts returned to them, or they may issue a scrap order, in which case the parts are trashed. It takes about 6 weeks for them to decide, but you can have the parts returned to you if you request them and a scrap order is issued. There is value in understanding the failures to allow for future repairs after the warranty has expired.

 

[Daixiwen]

No they say the fuse was blown. They also say that it is the PHEV ECU that blew the fuse, and that part I really don't understand. I'll get the old parts back and have a look.
The other thing I don't understand is that it happened while I was in the car. If the fuse blew there I should have heard something shouldn't I? It's quite a big fuse.

 

[kenny256]

From your reporting of the car not starting, it seems that the tech would have initially seen P0C78 with the MUT scanner. The system wants to check and verify that HV is present after issuing the START command; after a time-out it will issue a HV fault.

DTC P0C78:
The PHEV-ECU sets diagnosis code No. P0C78 if the condenser [large capacitor in the Motor Control Unit] is pre-charged improperly when the drive battery system starts.

PROBABLE CAUSES:
Damaged harness or connector
Loose wire(s) or connector(s) or a fault in the high-voltage wiring harness
Blown main high-voltage fuse
The drive battery fails: The energisation circuit system/high-voltage circuit of the main contactor (P), (N) or the charging contactor fails (loose high-voltage wiring harness wire or bus bar), or the main contactor (P), (N) or the charging contactor itself fails.
Malfunction of electric heater <Vehicles with electric heater>
Malfunction of A/C control panel (A/C-ECU)
Malfunction of A/C compressor
Malfunction of on board charger/DC-DC converter
Malfunction of pre-charge resistance
Malfunction of PDU
Malfunction of rear EMCU
Malfunction of PHEV-ECU

i wonder if they followed thru all the steps of the troubleshooting or just tried clearing codes without checking the necessary items? Seems like they are using the parts cannon to troubleshoot.

P0C78 troubleshooting steps:
http://mmc-manuals.ru/manuals/outlander_phev/online/Service_Manual_2014/2016/54/html/M154923210001901ENG.HTM


PHEV-ECU codes chart:
http://mmc-manuals.ru/manuals/outlander_phev/online/Service_Manual_2014/2016/54/html/M154920060027500ENG.HTM

 

[chrisv]

Hi
My 2015 GX4H PHEV is 8.5 years old 42000 miles on the clock, mainly done on electricity (i charge at home in UK off a 3 pin plug)
Having read about how a duff Aux Battery can cause so many problems I was worried about mine given its age, and while I could not easily get at both battery terminals I tested the Aux power socket in the arm rest while the radio and auxiliaries etc were on, with my £10 multi-meter.
Result was a very reassuring 12.66 volts which I understand from the forum is pretty good. I now have a note in my diary to repeat the test every 6 months.

 

[kenny256]

Use your very expensive meter and measure directly across the 12V battery terminals with the Key in OFF position, that will give you the open circuit voltage. If your 12V battery is the original OEM from when the car was new, then you have gotten your money's worth and then some. Congrats.

 

[Daixiwen]

You can easily access a battery terminal in the main fuse box near the engine (see in your manual how to jump start the car). You can use the chassis as negative terminal, and the metallic terminal under the red plastic cover as positive.

 

[RenssieB]

From your reporting of the car not starting, it seems that the tech would have initially seen P0C78 with the MUT scanner. The system wants to check and verify that HV is present after issuing the START command; after a time-out it will issue a HV fault.

DTC P0C78:
The PHEV-ECU sets diagnosis code No. P0C78 if the condenser [large capacitor in the Motor Control Unit] is pre-charged improperly when the drive battery system starts.

PROBABLE CAUSES:
Damaged harness or connector
Loose wire(s) or connector(s) or a fault in the high-voltage wiring harness
Blown main high-voltage fuse
The drive battery fails: The energisation circuit system/high-voltage circuit of the main contactor (P), (N) or the charging contactor fails (loose high-voltage wiring harness wire or bus bar), or the main contactor (P), (N) or the charging contactor itself fails.
Malfunction of electric heater <Vehicles with electric heater>
Malfunction of A/C control panel (A/C-ECU)
Malfunction of A/C compressor
Malfunction of on board charger/DC-DC converter
Malfunction of pre-charge resistance
Malfunction of PDU
Malfunction of rear EMCU
Malfunction of PHEV-ECU

i wonder if they followed thru all the steps of the troubleshooting or just tried clearing codes without checking the necessary items? Seems like they are using the parts cannon to troubleshoot.

P0C78 troubleshooting steps:
http://mmc-manuals.ru/manuals/outla...ual_2014/2016/54/html/M154923210001901ENG.HTM


PHEV-ECU codes chart:
http://mmc-manuals.ru/manuals/outla...ual_2014/2016/54/html/M154920060027500ENG.HTM

So by replacing the condensor, it wil work again?

 

[Daixiwen]

No it's most probably not the capacitor, and if you read the message again you will see a list of probable causes. In my case it was the PHEV-ECU, the main fuse and the main contactor in the battery pack. What happened probably is the following:
- the PHEV-ECU failed, maybe because of the low aux battery voltage
- the PHEV-ECU didn't control the main contactor correctly, preventing the high voltage capacitors from slowly charging through the pre-charge resistor
- this caused a spike of current when the main contactor connected the high voltage battery to the system, blowing the fuse
- this also caused wear in the main contactor, which failed a few days later

The main contactor was replaced under the battery warranty, but not the fuse or the ECU, which I had to pay for..

 

[yardbird]

For any 7.5 year old OEM 12V battery, you got your money worth. I usually change the 12V battery no more than every 5 years regardless whether it is 12.5 or 13 V at readings. It is not worth to save that $250 battery.