Gearbox/transmission module fault

[tacticalx86]

Bought a used BMW 320i automatic from a dealer end of May. I hit a pothole recently and the tyre on the driver's front nearside was funny so i took it in to a garage, expecting something like the wheel needing realigning or the shocks/suspension links having gone. (turns out the tyre was just over inflated). However in the course of diagnosis they told me the gearbox module/transmission module had an issue with it. They didn't appear to know much about it, and suggested i take it to a a garage which specialises in bmws. The thing is i've had absolutely zero issues with gear shifts and there's no warning light on the dash. Does anyone here know much about these modules? I'm under the impression that whilst the device doesn't cost that much itself, the gearbox would need to be rebuilt or replaced entirely which would obviously be phenonemally expensive. The car has until about august 25th on warranty but usually they want a quote first, and getting a diagnosis/investigation from a bmw garage (not an official one) will cost £60-£100. Just wondering if there is an issue, will it need to be replaced? I'm guessign eventually but I kept my last car for about 3 years with a broken synchro and it never got worse. Or could the obd message be an error, as there is no warning light on the dash? It was serviced and MOTed when I bought it and no faults.

 

[tacticalx86]

How old is the car? Was it a local dealer (assuming so) or a BMW dealer?

Try get a code reader on it if you can, clear it and give it a day or so of driving. Might just be an erroneous code.

12 years. Yes local dealer. Warrantywise warranty which doesn't seem worth the paper it's written on

Where can I get a code reader from?

 

[tacticalx86]

How many miles? I’d try and clear it with a code reader first and see how you get on. There are cheap ones available on Amazon and eBay.

74k.
I did notice today it did seem to take longer going from say 30 to 40, but might have been imagining it

 

[tacticalx86]

You can start noticing that they need a service when they’re at that sort of mileage. Wouldn’t worry too much about that though, but get a code reader and reset it and keep your eye on it.

It was serviced when I bought it tbf.
It seems transmission errors do show up on the dashboard warning system though.

 

[tacticalx86]

Gearbox service, I meant.

Didn't know that was a thing! Thanks might consider it, could well need a fluid change i suppose

 

[tacticalx86]

Ok so I've noticed two times in the last few weeks including tonight my car has had issues slowing down. This is where I start breaking and brake but the car continues to shift forward. Tonight it was at a set of red lights, thankfully no other cars around. Can a bad TCM cause this? The brakepads both front and back were replaced recently.

 

[tacticalx86]

A transmission control module implies it's an electronic component, in which case it would just be its replacement and not a gearbox rebuild. Obviously if this module is faulty it could be causing unusual behaviour in the gearbox.

The garage I went to (not a BMW specialist just the one which found the error code) suggested it would be?

 

[tacticalx86]

It depends on the car and the gearbox used. When I was looking at purchasing a Skoda, the lower end autos had a "gearbox for life" so nothing needed doing unless it went faulty. On the higher end models, VRS spec etc then it was a 40k recommendation (and some year time) to change the oil in the gearbox.

A quick Google search of your car and model details should find if it needs doing or not.

it's an automatic gearbox

 

[tacticalx86]

Alright so I think I definitely have an issue and its actually dangerous.

First time was a couple weeks ago, braked approaching traffic light turning to amber/red, and the car just wouldnt stop. it was still going about 1mph even with the brakes flat to the floor.
Second time last night, another st of traffic lights, same thing.
Took the car to a garage this morning, they found no issue whatsoever with the brakes or brakepads.

 

[tacticalx86]

Then this is nothing to do with your gearbox. If your car continues to move forward despite you having full pressure on the brakes - it is your brakes at fault. Your brakes are *easily* able to win the battle between your engine/gearbox wanting to go forward and your brakes trying to stop you.

When you said your brakes are "flat to the floor" I'm assuming that was just a turn of phrase, and your brake pedal feels firm, consistent and with no dead spots at the top of the pedal?

I went to the garage today and they said the brakes are absolutely fine. I spoke to a transmission place and he said the same, that the brakes would override any gearbox transmission fault.
The brake pedal feels a lot more ...effective? I don't know if thats the right word, on the left hand side than the right. as in when i was testing it after the garage today, when I had my foot down on the left hand side of the brake pedal, it was like emergency stop, on the right hand side, the side I normally put my foot down on, its a more gradual stop.

 

[tacticalx86]

A brake pedal should not feel more effective one side or the other, so either it's your braking technique, i.e. the way you are pushing the pedal down, causing this sensation, or you have a mechanical fault in the brake pedal.

Really at a loss what to do. I'm already booked in at another place friday, just a standard garage which did the brake pads for me, ironically these issues didnt' start until they'd put the new ones in. But if they say there's nothing wrong with the brakes too, I don't know.

 

[tacticalx86]

ok from limited experience ,having had mainly autos for the last 20 odd years. when you apply the brakes press the pedal in the centre , (it should make no difference at all as the brakes either work or dont, its one rod working the hydraulics)
when you say the car tries to shift forwards when braking, do you mean that when stationary its trying to move forward almost surging?.
we have this with our new c max auto where at lights it tries to move forward against the brakes, never had it before on autos but when approaching a auto gearbox specialist they stated its common with the newer type boxes ? meh.
doesnt really bother us.
as folk have said the error code was probably and old code never cleared, whenever the family get a newer car i always read all codes and clear them, then re read them a month later to see if any reappear. more often or not they dont, with modern cars the state of batteries can cause all sorts of spurious codes to appear.
i wonder if you are braking to a stop at the lights and then letting your pressure off the pedal slightly allowing it to try to move forward. i always keep my left foot tucked across the front of the seat and just use my right foot either brake or accelarator, it was how i was taught when i started driving autos for a large private hire company, and i have kept doing it.

these sort of problems can really start to annoy you and eventually spoil the car for you ,i hope you resolve it good luck.

No I don't mean that, it is trying to move when my foot is down on the brake. It is not getting to the point where its stationary. I brake and brake but it continues to move like it's got a mind of it's own

 

[tacticalx86]

is this your post?

https://www.honestjohn.co.uk/forum/post/198601/bmw-320i-f30---car

if not then there must be others with same problem?

Aye, its me

 

[tacticalx86]

I probably wouldn't say this to the garage as they may just dismiss it as all in your head because this is impossible. The pedal pad your foot touches is connected to the metal rod which is connected to a single rod.

There's a possibility that there could be air in the system but this would result in a sloppy pedal which would firm up temporarily when it had one or two pumps to it. The fact you're saying that you've got your foot flat on the brakes as hard as you can and the car is still going forward is 100% an issue with the brakes. No matter what hypothetical fault is with the gearbox, the brakes should stop your car without breaking a sweat and keep it stopped. Also, it seems very coincidental that you had work done on the brakes and now the car sometimes doesn't stop.

How often does this happen?

Does it only happen as you pull up to junctions or traffic lights or does it happen when you're driving along and you sometimes feel the brakes aren't effectively slowing you?

When you are in the situation where you've got your foot hard on the brake and the car is creeping forward, what do you do to stop the car? If you release and reapply the brakes does it cause the car to subsequently stop?

Do you ever feel the pedal is inconsistent? For example, does the top of the pedal sometimes feel a soft, but other times it feels firm and sharp?

I've noticed in general the brakes don't feel that good when slowing down when driving along but failing to actually come to a complete stop has only happened twice , when coming up to junctions. I try and use the handbrake and it still moves, eventually after keeping my foot down the car does stop

 

[tacticalx86]

Can you explain a bit more what you mean by this? When are you applying the handbrake and isn't this car an automatic?

Only applying the handbrake in the situations described where the car won't stop when I'm just using the brake pedal.

 

[tacticalx86]

So I took it to the specialist. They're saying one of the calipers (rear) is getting stuck, and the brake fluid level is too high and of low quality

 

[tacticalx86]

I wouldn't have thought any of that would make the car completely incapable of being stopped at low speeds. The fronts do most of the work, too much fluid in the res is really here nor there and you could replace your fluid with cooking oil and it would still "work" for a time at least.

You mentioned in your coolant thread that you didn't know if it had ever had a major service so if the fluid hasn't been changed in over a decade then it's worth getting it changed anyway but again unless you're cooking the brakes and heating up the fluid until the moisture in it starts to boil I'm still not so sure it would be the root of your issues.

It's the only thing I really think it could be and the fact its only happened since getting the rear brake pads done

 

[tacticalx86]

I wouldn't have thought any of that would make the car completely incapable of being stopped at low speeds. The fronts do most of the work, too much fluid in the res is really here nor there and you could replace your fluid with cooking oil and it would still "work" for a time at least.

You mentioned in your coolant thread that you didn't know if it had ever had a major service so if the fluid hasn't been changed in over a decade then it's worth getting it changed anyway but again unless you're cooking the brakes and heating up the fluid until the moisture in it starts to boil I'm still not so sure it would be the root of your issues.

Do you have any theories then?
I'm getting conflicitng advice about the transmission, one mechanic thought it could be as could someone on another forum, another mechanic said it wouldn't be and the brakes would override etc as did someone on here. Maybe a cylinder leak? But I'm sure it would have been found.

I will get the repairs done anyway, but assuming this issue continues and remains undiagnosed, what is the best way to stop the car, as I recall I tried using the handbrake but it still kept moving.

 

[tacticalx86]

Garage says copper grease was put on the front brake pads which shouldn't be used, whichb

 

[tacticalx86]

Yeh that ain't going to be it unless someone put copper grease on the pad faces or disc. It's not good to use copper grease because of it's effects over time on rubber such as the brake piston seal, but we're talking years to deteriorate the rubber and even then that wouldn't make the car not stop.

If this started with the rear pads I think you should be looking at that. What brand are the rear pads for a start? Are they Eicher or some dumpweed like that? The reservoir was probably overfilled because the garage who fitted the brake pads pushed the caliper pistons in to accommodate the new thick pads and didn't drain off the excess brake fluid. Nothing more than that.

I'll get them to clarify but they said something about copper not mixing well and when it was getting heated the brakes were seizing jon

I've got no idea.

The technician who diagnosed it was the same one who did the rear pads, he said the brake fluid needs changing and the front brake pads and discs need replacing. He also said if the other garage had said about getting the caliper replaced we could but he didn't see anything obviously wrong with it