MG4 - Crash repair: Questions and then repairs

[RoadTest]

First off, a thank-you to the many posters here on the forum - and most particularly to the gentleman who shares the workshop guides on his website. These have all been invaluable.

Background: Own an MG4 as daily driver - works well no complaints. I recently crashed the car at high speed. Airbags deployed, HV battery cut-off engaged. I am now in a position where I must repair the vehicle, performing most works myself.

Spoiler: Car crash image

Note: There are many codes to investigate and clear. I'm still waiting on a more fully-featured scanning tool update to make mine compatible with the MG 4.

Question 1 & 2: Does the MG4 have a pyro fuse & where is it located? There has been conflicting information here on the forum and I do not have a strong sense either way.

Observation 1: The "General Workshop Procedures" manual does at no point mention a pyro-fuse. It does however mention, on page 973, mention a "High-Voltage Power Distribution Unit Fuse" within the Power Distribution Unit (PDU) held in by 6 screws.
I believe the HV-PDU fuse to be this cluster of 3 fuses, rated at DC 500V, 60A (Please see below image). I initially had some confusion as the manual referred to a single fuse. These fuses still have continuity.

Spoiler: Suspected HV PDU fuse

Observation 2: The only other fuse of significant note mentioned is in the Energy Storage System (ESS), which appears to be a way of referring to the Battery Management System (BMS) and the physical battery itself. According to the EH32 Service Circuit Diagrams, there appears to be a 500A, J-Case style fuse (see screenshot below). Being a J-Case style fuse, this is unlikely also to be the pyro-fuse, correct?

Spoiler: ESS circuit diagram screenshot

I am keen for other posters to share their thoughts and observations. I'm happy to document the process as I go about repairing the vehicle.
So far, I must: Reflash the SRS-Airbag computer, replace safety devices (airbags, seatbelts and crash sensors), address / clear codes and potentially rectify the pyro-fuse situation.
And after that, physical works including steering and suspension repairs.
Finally, pay increasingly larger sums of money to the panel-works professionals.

 

[siteguru]

Is the pyro fuse not normally located underneath the car? In the MG4 it may even be part of the battery pack assembly, so accessible underneath the car behind a panel.

A read of this thread may be helpful:

Post in thread 'MG 4/Mulan after crash. Drive with deployed airbags. Crash reset. Cable and Software.'

Apr 2, 2024

Progress till now.
All 4 seatbelts are fixed as standard no pyro safe belts. Front airbags are unmounted. All 6 blown pyro are replaced with resistance 2.2ohm to test srs module when is fixed.
Front radar is fixed temporary.
Front gaps are fixed. Bumper and hood need some more filler and correct paint.

• chiMol

• 

Furthermore, ChatGPT gave me this response ...

Where is the pyro fuse located? Reply in English please

ChatGPT said:​

The pyro fuse in the MG4 EV is part of the High Voltage (HV) Power Distribution Unit (PDU). To access and remove the PDU fuse—which includes the pyro fuse—you need to:

1. Turn off the start switch and wait more than 5 minutes.
2. Remove the manual service disconnect.
3. Remove the rear seat cushion.
4. Detach 12 bolts to remove the rear floor subassembly.
5. Remove 8 bolts to open the upper cover of the HV PDU.
6. Remove 6 screws fixing the PDU fuse to the unit.

This indicates that the pyro fuse is physically located within the HV Power Distribution Unit, which is situated above the HV battery pack and under the rear floor section of the vehicle.

 

[salty]

To the forum. Glad your ok, after the accident. And good luck with the repairs.

 

[kozd]

Mg4 havent got a pyro fuse that deploys after aciddent. The fuses you mention wont gonna deploy in a crash. You need to clear crash data at airbag module with diagnostic tools and hourly paid diagnostic software by saic. There was a trick to drive the car i cant remember it was something like disconnecting and connecting airbag module and after connecting you fasty get car to drive and it can drive like that after locking it you need to do it again.

 

[T1 Terry]

Under the centre console there is crash module, unplug that and it all comes good. There are people who can reflash these modules rather than pay out the big $$ for a genuine replacement.
This bloke has used a different model front wheel drive MG EV to repower his 928 Porche, but I believe the module placement under the centre consul is similar in the MG4 https://www.youtube.com/results?search_query=928+v8+ev+eposode+1 ..... you might need to play them at 2x speed to get to the bits you need, but over all .... if you have trouble sleeping, this might help

T1 Terry

 

[hojnikb]

At this point; is it even economical to fix the car (even by yourself) ?

Might be better off to part the car out (there's lots of good components worth money) and just buy a used, uncrashed one?

 

[Rolfe]

I think the answer to that last question depends on whether you value your labour time. I recall @chiMol saying that for him it was a labour of love and he enjoyed doing it, so he didn't count the time he spent on it.

 

[hojnikb]

I think the answer to that last question depends on whether you value your labour time. I recall @chiMol saying that for him it was a labour of love and he enjoyed doing it, so he didn't count the time he spent on it.

Even so; the parts cost alone might not be worth it. Things like doors and fenders can be pretty expensive to source; and not to say all the other stuff, that can hide under the bonnet. And bodywork/paintwork etc etc..

 

[T1 Terry]

Even so; the parts cost alone might not be worth it. Things like doors and fenders can be pretty expensive to source; and not to say all the other stuff, that can hide under the bonnet. And bodywork/paintwork etc etc..

This member is in Australia, second hand parts are slowly making it onto the market but a complete crashed MG4 EV with very low kms on the clock can be bought relatively cheaply at the salvage auctions ..... so no real money to be made parting it out ...... If it hasn't been marked as a repairable write off or total write off is a rare item .... I'd be repairing it if it were mine

T1 Terry

 

[RoadTest]

Apologies for the lack of update - recovery post crash has been challenging, I hit my head rather hard.
To address posts by others; you are correct, it would be best to not undertake this challenge - it is likely not economically feasible. Sadly due to a combination of factors, all of my own doing, I am in the position of having to do this. I have now had time to address the damages to the vehicle.

A special thanks to those members who have shared their knowledge on this forum and this thread - it has been invaluable.

From my own investigation and resources like this forum and the excellent "General workshop procedures" guide, I came to the conclusion that there was no pyro-fuse that had detonated in this case. I am still generally unsure IF there is a pyro-fuse in the MG4.
If the battery / HV circuit is intact and functional then I can repair the car.

I have the following issues to face:
Issues: SRS collision computer causing imobilisation, Deflated/poor seal front 2 tyres, Bent right / driver steering components, shattered driver / right disc rotor, deployed driver seat air bag, deployed right side curtain airbag, deployed 4x seat belts. Extensive exterior panel damage.

The order of operations then was the following:

Repair / reflash the SRS / collision computer (Located underneath the front center console).

Spoiler: SRS computer

This was not difficult just a physically awkward process to undertake.
It was held in place by 3 nuts and two harness connectors.
I sent it to a RaceEvo Australia to be reflashed / have the crash data removed. Raceevo website at a cost of ~$190.
Time taken was less than a week and I found him to be polite and helpful.

Purchase vehicle interface device / VNCI - VDI3 device

Spoiler: VDI3 device - On Aliexpress

I purchased the above device from Aliexpress as recommended on this forum and paid ~$250 AUD including shipping. It would do well to purchase this part in advance due to delays in shipping.


Download workshop software and purchase license to connect to vehicle ECUs to determine if any further issues.
From my understanding, once the SRS computer is fixed and codes have been cleared, the vehicle should be able to move. Note: Ofcourse many / most codes will return upon vehicle re-start.

I would recommend all interested parties going down this road to read this thread in its entirety:

Thread 'Diagnostic VDI, VNCI, MDI with MG4'

Jul 14, 2024

[ Edit moderator: Links to various useful posts for quick access. Mention @Coulomb to have more links added.

A tutorial guide for software updates.

Trophy/Luxury 22/23 FICM loading guide (separate thread).

The various SAIC server access plans and costs.

An inexpensive VDI dongle needed for any update work. See a few posts later for alternatives.

An alternative TBOX updating method using a USB stick and SIPS.

]

Hi all my other cars I have/the wife has owned I've had the diagnostic interface & dealer software

Like
Tech2 & TIS2000 for Saab
MDI &...

• haloweenhamster
• diagnostic interface mg4 software
• Replies: 766
• Forum: MG4 EV Forum

• 

This post in particular is key for guidance:

Post in thread 'Diagnostic VDI, VNCI, MDI with MG4'

Sep 23, 2024

There was a comment about a guide for software updates so I thought I'd write it here where all the other info is

To connect to the car you need a Vehicle Diagnostic Interface (VDI), from what I've read a VDI2 or VDI3 for MG4, I personally ended up getting a VNCI due to supply issues, it's also substantually cheaper

VNCI VDI3 Rongwei MG Wuling Baojun Datong Diagnostic Interface Compatible with OEM Software Driver

VNCI VDI3 Rongwei MG Wuling Baojun Datong diagnostic interface is compatible with OEM software driver, plug and play. It can be an alternative genuine VDI3 diagnostic interface.

www.vncistore.eu

it's recommended to update connected via USB but I have done some connected via WiFi which worked fine

Once you have the interface you need to install the software on a windows computer, VCI manager &...

• haloweenhamster

• 
• 
• 

Spoiler: Computer time

I have so far only needed to purchase 1 day of license. I suspect I will need one more at the end of this process.
I found the process for obtaining the software to be straightforward, and I found the website where you purchase the license for the software to be convoluted, but not impossible.
The software worked well and without issue with the VDI interface device purchased above.
I downloaded the codes present -> ~150 codes.
I cleared the codes and was left with ~30.
The vehicle would now move under its own power and with 'most' functions enabled.



From this information I have the following list of things to do:
Repair 2x front wheels -> STATUS: Done. This was easy to accomplish at a local tyre shop.

Replace Driver/Right tie rod, inner and outer -> STATUS: Done.

Spoiler: Unhappy Tie Rod

This was not particularly hard to do, though the process was awkward.
Removing the inner tie rod from the steering rack requires either a special tie-rod removal tool or a 38mm spanner. I purchased a spanner on Amazon AU for $30.
I had to purchase from MG Dealer: Inner Tie Rod + Outer Tie Rod + tie rod boot. All up ~ $250 AUD.
The tie rod knuckle required an 18mm wrench and 8mm socket.
Please be advised that the staying nut for the outer tie rod is not included in the MG 'kit' and must be harvested from the original equipment.
The boot does include a classic clamp for the tie rod boot.

Replace disc rotors -> STATUS: Done. Easy to do.

Spoiler: 2-piece brake rotors

The process is easy enough to perform if you have replaced brakes / rotors before.
MG manual suggests rotors should be replaced as pairs and this reflects conventional wisdom.
MG dealer quoted price of two rotors at ~$550AUD. I paid what they asked and still feel dissapointed in myself.

Replace right / driver disc caliper bracket -> STATUS: Waiting for parts.

Spoiler: Hairline crack in brake bracket

I discovered when replacing the disc rotors that the caliper bracket had become cracked and was therefore unsafe and unusable.
This will be easy to replace when the part arrives.
I purchased a replacement part from Melbourne City Wreckers. ~$200 AUD.

Replace driver / right seat airbag -> STATUS: Parts received, awaiting installation, significant issues ahead.
As the airbag had deployed, I opted to replace the whole chair with one from the wreckers.
Melbourne City Wreckers: ~$480 AUD.
Overall I think I made a mistake doing this, and would discourage others or atleast recommend further caution.
My vehicle is the 'budget' model with manual adjustments and 3 under-seat connectors; airbag, occupancy sensor and seat belt sensor.
The seat I received has electromechanical adjustments and one large bulk underseat connector as well as the expected separate seat airbag connector.
I am unsure if I'll be able to hack apart the harness and make it work on my car, OR simply cut out the airbag and integrate it into my existing chair.
Overall I have needlessly complicated an already complex operation through carelessness.
If someone possesses wisdom regarding the chair pinouts or harness it would be appreciated - otherwise I'll check the workshop manual when the time comes.

Replace 4x seatbelt modules -> STATUS: Parts received, awaiting installation.
Melbourne city wreckers: ~$800 all up. ~$200/unit.

Replace side impact sensor -> STATUS: Awaiting parts.
Purchased on eBay, from UK vendor. ~$120AUD. Part #109587232023
Easy to replace - part to be bolted into base of vehicle B-pillar.

Replace right side curtain airbag -> STATUS: Awaiting parts.
This part was frustrating to source. I anticipate installation will be just as challenging.
Melbourne wreckers, ~$310 AUD.

Once all of these items have been completed, the car should be in a serviceable condition.
Ofcourse, many, many thousands of dollars of panel repair work will need to be performed. I weep for my wallet.
I will perhaps update this when works are completed.
If you have follow-up questions, please ask away.

 

[Cabansail]

Can one ask, why was the car not insured?