Place bets now...

[ptruman]

CEL light back on, this time on the M40 on the way home.

The other day the car felt like it slipped when upshifting once, but was otherwise ok.
It was fine getting to the M40 (inc a good 70mph run down a dual carriageway) - but on the M40, a slight 'slip' or push feel, on comes the CEL and loss of power.

Car still drove at the limit, and was shifting, but wasn't doing so with any oomph.

As approaching home, got to slow down/islands etc, and it seemed to be holding onto revs a lot more before shifting up, and "engine braking" more (slowing down faster).

Got back home, and restarted car. CEL still on, but power returned - although still seems to be upshifting late, and even seems to do an extra shift down before applying power. When I tap the accelerator (at high revs) I think I can hear a slight 'click' noise under the car (doesn't do it below 40mph).

Given it's after 7pm I can't go get the codes read, but my wifes car is going in on Saturday for a service, so I might get mine read at the same time.

So, place bets now. Have I:
a) narked off the injectors when I had my Brabus connection error?
b) got a failed/failing TCU? (speed sensor/plate etc)
c) lost a gear?
d) other....

 

[PobodY]

I'm going with (b) and guess the electroplate (although maybe yours is a bit late for this problem).

If it refuses to select the right gear, it feels like the engine has no power.

 

[ptruman]

It seemed to shift with the paddles but just didn't accelerate hard, like the turbo wasnt there. After reset it's accelerating ok but isn't shifting when it normally does.

Typical slow speed upshift from standstill was at 8mph and 2000rpm ish, now it's nearer 20 mph and 3000rpm.

 

[wu56Shoozz]

Turbo actuator, the car has gone into Limp Home mode.. hence no delivery of power and takes an age to get up to speed..

 

[sturgeon]

d. Needs ATF and filter change plus software update via Star - post Brabus installation. (?)

 

[ptruman]

Would that have produced the "slip" feel?
Also it's accelerating fine now, just not upshifting where it should. Taking it in for a STAR check in an hour or so.

 

[ptruman]

d. Needs ATF and filter change plus software update via Star - post Brabus installation. (?)

You may be partially right...
The car is reporting rail pressure too high. For now, we've removed the box (connections, the harness & box are still in the car, just not connected) and cleared the code - and it's driving ok (just with no 'oomph').

Full XENTRY report shows the rest of the car has no errors (although one stored code on a door lock actuator, and warnings about radar interference from when I drove past Jodrell Bank...) - the ATF service was done just over a month ago, so should be ok.

Garage did indicate that the box will be fiddling with the pressure, but the ECU will still be looking for tolerances, which may be exceeded. They did allude to some screens in STAR/XENTRY they don't have access to, and maybe MB do "tell" the ECU that box is there - and that most remaps would (likely) amend the pressure tolerances also.

So, does anyone know if an MB install of a Brabus does include any S/W mods to the car/ECU? (if so, why not just mod the ECU in the first place...)
The Brabus fitting instructions don't refer to any car fiddling other than harness fitment... (I've ping Brabus an email to see if they may answer that one).

So, options here are:
1) Run car without box - check if the error comes back - there may be an error with a rail pressure sensor, you never know...
2) If it doesn't reoccur - issue is linked to box - so:
2a) See if a car s/w update IS (or is not) needed - and if you can get it without paying extortionate fees
2b) Sell the box on/get a remap...

 

[ptruman]

Quick update : Brabus have replied and said it can be caused by wear on the fuel high pressure pump, which can occur on higher mileage vehicles.

This may be why MB don't warranty them over 60K miles when fitted "after factory" perhaps? I suspect changing the pump is "a job" however and prob has some ££ attached there?

They've also said the box can be sent in for a check and re-programming.