RSB Service Required - Code P1A44 and P1A46 - Technical question

[Phevanna]

Hello guys,

"EV System Service required" "RBS Service required stop safely", car went into limp mode (lower power) and was driven only by the EV system, no IC engine "kick in" despite press full throttle and drive battery showing 1 mile range, so I keep it going on limp mode until run out of drive battery and car stops, turn off, turn on again, got the ready message, IC engine starts, put in D and drove 2 seconds and same message on dash, IC engine cut out and car stop again. I am able to start the car and it keeps for 3 seconds and cut out the IC engine.
I have ODB tool with me and read the code, only code is BMU P1A44 which is Ground Detection Fault, I cleared the code but it shows again and again.

Thanks

 

[AndyInOz]

You can't drive the car without the EV system.

The engine can only directly provide power to the front wheels over a certain speed (80 km/h IIRC).

Re the ground fault, check for ground cables that have been damaged or destroyed during your 'slow drift'.

My instinct is that you will have water in the battery box, either through damage to the case, or via submersion.

My advice ends here because you don't want to be told to take it to a dealer.

 

[kenny256]

As you probably already know, RBS is the Regenerative Braking System which puts energy back into the HV battery pack when coasting.

Inside the pack is an electronics module which checks for very small leakage current (10's of microAmps) between the HV battery and the chassis, and mits calls this the ground fault detection indicated by your DTC.

i don't know how much ground clearance there might be up to the HV battery case, and i would have assumed that it is a somewhat sealed box, but it would probably leak around the wiring cable harness feed-thru joints. Probably have rubber seals and glands at feed-thru, but not water-proof.

Water would provide a conductive path during the leakage check and trigger the fault. The fault will likely clear on its own if the moisture can be eliminated.

Here is a link to the P1A44 troubleshooting, http://mmc-manuals.ru/manuals/outlander_phev/online/Service_Manual_2014/2016/54/html/M154945050018101ENG.HTM

ps This fault could occur if the A/C compressor were to get wet also, so it doesn't necessarily mean water got into the pack, but any of the external HV consumer devices are suspect also. Get some warm dry air blowing under there and dry that thang out.

 

[Phevanna]

Thanks for the link kenny256

I am suspecting water too and due sharp turn to the left during my drift, some water pool located somewhere have moved and triggered the fault, because as I said, the car was fine after crossing the water, just got the fault after sharp turn and traction control actuated.
I had a ground leaking before on electric heater due fault at unit, I have disconnected the main power cables to it about 10 months ago and no problem since.
I will check the AC compressor too, I forgot about that.
Do you think a multimeter checking the resistance between each connection point inside the RMCU/PMU and chassis will show where the ground leakage is?

 

[DaveL59]

worth checking that the sealing plugs/grommets/bungs are still in place under the battery box, 3 each side if I recall correctly. One of those gone would allow water in and would cause issues. There's nothing to protect those sealing grommets/bungs from mechanical interference so if you grounded the bottom of the car even slightly on the grass one could have come away.

 

[littlescrote]

The earth strap between body and rear diff is of poor quality and corrodes, is yours still intact?

 

[kenny256]

...
Do you think a multimeter checking the resistance between each connection point inside the RMCU/PMU and chassis will show where the ground leakage is?

i think it might take a "megger", a special meter for measuring very high insulation resistances (Meg Ohms), to even get any sort of a reading, and then it is an average reading over a broad path not likely to pinpoint specific locations.

Until the moisture is gone there is not much that can be done with measurements.

i once did troubleshooting on a circuit board that experienced leakage thru a very high resistance such as this. It was found to have a high concentration of cleaning solvent residue on the board underneath the protective clearcoat layer; the board would "leak" current in the presence of high humidity in the air. During manufacturing the boards were cleaned and hung up to dry, where the last little drops of solvent would run to the edge and evaporate leaving an invisible microscopic trace of contamination that measured on the order of 5 MegOhms with the megger. It was only possible to find this because it affected one particular component and circuit on the board.

But in your case there is no specific pointer to a location. The troubleshooting has 42 steps just to identify potential locations for throwing the parts cannon at it.

It may take lots of alky-hawl to solve this problem, for cleaning and drying out connectors and cable ends where water may wick up behind the insulation, and for drowning your pain...

 

[Phevanna]

Yes you are right kenny256, a standard multimeter will not have the accuracy to test that resistance. I have checked this one on Amazon ANRIS UNI-T UT501A Insulation Resistance tester meter megger earth ground resistance Voltage Tester Megohmmeter Voltmeter + Backlight https://amzn.eu/d/7MmnizF
Looks like it have the range I need, 500V - 0MΩ~99.9MΩ ± (3%+5), what you think?
On troubleshooting steps, resistance tests show that we are looking for values of 10MΩ or more.
I didn’t have time to look the car yet, but it seats parked for last 5 days and code persists, I think if it was water, it should be dry by now.
I will have a look this weekend and see how it goes.

 

[daveg1966]

Just be careful using any form of insulation tester anywhere in the region of electronics. The high voltage generated by these instruments can fry sensitive electronics if used incorrectly. Normally all electronics are disconnected before megger testing - take it from someone who destroyed the control circuits on a high voltage industrial drive system once! You may of course be totally familiar with this, I just wanted to warn you and others if not.