Pothole gives MG4 concussion.

[geekas]

Pothole gives MG4 concussion.
Last Wednesday week I had reason to travel to Bunnings in Hastings, then on to Tyabb. Not well traveled destinations so I used the Great Google to navigate, but I missed a turn and it dutifully re-routed me. But the route followed some unsealed farm backroads and I had to pick my way around the potholes from the rain the night before. I thought I was doing pretty well when suddenly over a slight rise there was a muddy ditch right across the road. From 60k I hit the anchors hard, releasing as I reached the ditch to bring the nose up. WUMP! The MG's short and relatively hard suspension bottomed out and we lurched to the other side. A cacophony of alarms erupted from the dash telling me forward collision, cruse control, lane keeping, and anything else that involved sensors were off-line. I pulled over to inspect the damage. There was nothing bent or broken. Lifting the bonnet the only sign of the adventure was muddy water splashes here and there. Looking underneath the only sign of distress was the rear undertray sagged down with a collection of rocks jammed underneath it. Ok I thought, from this forum I know the MG undertrays are a known weak point, I'll look at it later. I turned the car off and locked and unlocked it hoping to reset the alarms. Nup. Still no sensors. But it did drive and felt normal with normal performance, just with orange warning lights all round the dash.
I continued to Hastings and found the item that the website said was in stock was not in stock and I would have to go to Mornington Bunnings. Ok then I will drop in to Mornington MG dealership (where I got the car)and ask questions there. But about half way there the alarms started to clear. One by one the services came back on line. The lane keeping I had to turn off like I always do, and the cruse worked normally. By the time I got to Mornington I had a normal display. So what went wrong? Had the severe jolt caused the G-sensor to send such data that it caused the safety processor to go into mumble mode? Has anyone else had a similar experience?

See the pothole? Neither did I. (The Forester is my old car I returned in the next day. It is sadly soon to be euthanised as it has untreatable cancer and sick gearbox.)

The pothole up close. The old Forester didn't know it was there.

 

[decrep]

Could be you got a bit of water around the sensors, which subsequently dried out. Just a theory off the top of my head

 

[tsedge]

It is normal for the driver assistance systems to progressively reset after a problem - this can be seen, for example, after a 12V battery disconnect and reconnect.

It is not clear what happened in your case, but clearly the impact caused some interruption or other problem with some of the sensors.

If there is truly nothing bent or broken, it should be ok but I'd recommend a thorough inspection of the suspension and chassis to be sure.

 

[MEH]

Don't forget claiming off the council, assuming the road is adopted

 

[geekas]

Don't forget claiming of the council, assuming the road is adopted

Not in Australia. It would need an insurance claim and then the local council to be sued. I havn't heared of a successful claim for this so far.

Could be you got a bit of water around the sensors, which subsequently dried out. Just a theory off the top of my head

Yes I thought of that too, but there are 3 cameras, the nose radar, and the G sensor involved AFAIK, and the only ones affectible by muddy water was the side mirrors. If water gets in elsewhere then it's a worry for long-tem reliability.

It is normal for the driver assistance systems to progressively reset after a problem - this can be seen, for example, after a 12V battery disconnect and reconnect.

It is not clear what happened in your case, but clearly the impact caused some interruption or other problem with some of the sensors.

If there is truly nothing bent or broken, it should be ok but I'd recommend a thorough inspection of the suspension and chassis to be sure.

Hmm, on washboard Australian outback roads I have heard of battery collapse where the battery inards basically fall apart. Maybe there was momentary battery disconnect or short due to the jolt, but I would expect loss of the displays momentaraly as well. Maybe so short their filter caps held them up?

 

[gazza487]

Not my 4 but a petrol 6 in the house. If you unsettle the abs in that thing all hell breaks lose and the succession of bings sounds like an electronic version of Big Ben. Bing bing bing bing.

Basically once the abs is unsettled lots of other systems shut down as the ability for them to work relies on read out of wheel speed for other calculations I.e how hard should the system brake for example. If the abs stops getting reliable data it shuts down and goes dumb (better to have standard brakes than keeping the modulator going and cutting brake pressure for example) ergo other bits that abs modulator activate - it knows they won’t work so warns you x service is out of action. The amount of data floating around cars networks is crazy (and has been for 20 years).

20 year old Chrysler, small seal on the intake would take out cruise control but not fire the engine management light (I bought a load of the egr seals from USA). A dodgey read from the rear offside resulted in the gearbox complaining about shifting (turns out it used speed data compared to input shaft speed on the box).

The 6 had a broken abs sensor wire. Abs gone which resulted in no speed signal (despite the speedo working from a drive on the box) which killed off tpms, cruise control, adaptive wipers defaulted to normal, stability control and the inbuilt satnav became a bit flaky.

Its programmed safety features/defaults. So long as nothing is physically broken I’d say you may be good with a wash down, battery off if necessary and watch for any further faults arising.

G: sensors are normally linked straight to SRS module which is combined with speed data and occupancy data from a body controller so it knows how or if it should fire airbags. Unlikely that has been part of the issue as I’m sure you’d know about it. Nothing is impossible though - seriously complicated machine we drive now (EV or otherwise).

 

[geekas]

Not my 4 but a petrol 6 in the house. If you unsettle the abs in that thing all hell breaks lose and the succession of bings sounds like an electronic version of Big Ben. Bing bing bing bing.

Basically once the abs is unsettled lots of other systems shut down as the ability for them to work relies on read out of wheel speed for other calculations I.e how hard should the system brake for example. If the abs stops getting reliable data it shuts down and goes dumb (better to have standard brakes than keeping the modulator going and cutting brake pressure for example) ergo other bits that abs modulator activate - it knows they won’t work so warns you x service is out of action. The amount of data floating around cars networks is crazy (and has been for 20 years).

20 year old Chrysler, small seal on the intake would take out cruise control but not fire the engine management light (I bought a load of the egr seals from USA). A dodgey read from the rear offside resulted in the gearbox complaining about shifting (turns out it used speed data compared to input shaft speed on the box).

The 6 had a broken abs sensor wire. Abs gone which resulted in no speed signal (despite the speedo working from a drive on the box) which killed off tpms, cruise control, adaptive wipers defaulted to normal, stability control and the inbuilt satnav became a bit flaky.

Its programmed safety features/defaults. So long as nothing is physically broken I’d say you may be good with a wash down, battery off if necessary and watch for any further faults arising.

G: sensors are normally linked straight to SRS module which is combined with speed data and occupancy data from a body controller so it knows how or if it should fire airbags. Unlikely that has been part of the issue as I’m sure you’d know about it. Nothing is impossible though - seriously complicated machine we drive now (EV or otherwise).

Ahh yes, that makes sense actually. As I said when I saw the pothole late I hit the anchors hard but released them again before I actually hit. Although I don't remember ABS pulsing on the pedal, ABS was probably activated, and at the release would still be doing stuff when the wheels were thumped and probably thrown clear of the ground for a short distance. The resulting inconsistent wheel data might well have caused an ABS shutdown with the rest of the systems going out with the loss of ABS sensor data. ABS offline was one of the alarms. With further driving producing "normal" data the ABS probably reset, allowing the rest of the services to "see" the data again.
Still, I would like to have the ABS react more robustly to this scenario, not throw its hands over its head and hide.

 

[gazza487]

Ahh yes, that makes sense actually. As I said when I saw the pothole late I hit the anchors hard but released them again before I actually hit. Although I don't remember ABS pulsing on the pedal, ABS was probably activated, and at the release would still be doing stuff when the wheels were thumped and probably thrown clear of the ground for a short distance. The resulting inconsistent wheel data might well have caused an ABS shutdown with the rest of the systems going out with the loss of ABS sensor data. ABS offline was one of the alarms. With further driving producing "normal" data the ABS probably reset, allowing the rest of the services to "see" the data again.
Still, I would like to have the ABS react more robustly to this scenario, not throw its hands over its head and hide.

It’s weird but rest assured the systems are likely working best way they can to keep you in one bit. Below certain speeds the abs ceases to function or you’d never stop the car so you may have been below that and it fully knew you needed no assistance. Or equally the crazy info it may have been seeing at the time it has said - I’m going to make more of a mess of this situation as I think one wheel is doing 20km/hr and one doing 50. In the olden days my rover 75 would store a fault code of ‘implausible wheel rotation or similar’ - loads of them when I was interrogating it with T4. Asked someone and they said yep likely when it’s been on a lift at the garage and the wheels spinning.

Either way hope nothing is physically broken and you are motoring along safely.