Hi guys,

I have a spare key fob for my R56 Mini Cooper (2009) which does not start the car. Lock and Unlock is fully functional altough.
After a short check of the fobs electronic board, I could find one damaged component, most likely a capacitor.
The problem is that I cannot find out what exact component it is or how much capacity it has.

The following picature shows the damaged key:




Does anyone have an idea which excapt component (or capacitor) this is or does anyone have a schematic of this board? I think it is some kind of RC member, so replacing it with any capacitor may not work.

The PCP number of this board is 233.441.011-02.

Thanks a lot.

 

The PCB appears to have seen some fluid.

Clean off the component area with 90% isopropyl alcohol and a cotton swab. If the cleaned component and its copper pads on the board look okay but the solder joints are questionable, then resolder the component joints. Next, test the voltage of the battery, which I think should be 3V. If that's fine, retest the fob.

Given the fob has partial function but won't start the car, also inspect the solder joints of the large immobilizer chip visible in your picture. How does the coil look on the rear side of the PCB?

 

Thanks for your reply. That what's looking as fluid is the blown capacitor I think. I did clean everything and it fell apart. I cleaned everything and it looks good so far, except that I need to replace it now.
Also the coil looks good.

The battery had 2.82V, I already ordered a new one.

 

Post a pic of your cleaned up PCB in the area of interest.

The missing capacitor is not the electrolytic type that leaks. It's a ceramic capacitor. Did you save the old capacitor because it could be fine.

The comment below from the MINI Key Hospital is relevant to your question.

 

Here is a pic of the cleaned PCP, altough I think that is not what you meant :D
The capacitor did not leak, it did burst. (Also ceramic ones does burst).
It fell completly appart while gently touching, so no chance to get any information about it.



The comment from the Mini Key Hospital does not sound very confident that I could ever find out what size that capacitor has.

 

These remotes are useless to purchase used, as they cannot be reprogrammed once pair to a vehicle. If you are handy with soldering and repairing circuit boards, you “could” purchased a used one for sacrificial components….

 

Or, shoot me a PM. I have one for my donor car. The lock button is missing and I am not sure if it works but I would mail it to you for the price of postage.

Not sure if yours is rechargeable or a replaceable battery but, the one I have is rechargeable type,

 

Good luck with the fix, daxus!

If DogfaceSGM's key fob has a 233.441.011-02 PCB, then you can swap the capacitor of interest onto your PCB.

I also saw some 233.441.011-02 PCBs for sale on UK eBay, but the price of shipping would be high.

 

I saw a YouTube video where ^this issue was overcome by desoldering your current fob's large immobilizer chip and swapping it into a replacement PCB of the same type. However, you'll need advanced soldering skills and tools to remove and install that large chip.

 

Thanks everone for your ideas
That video would be interessting...
Soldering should not be that big deal, so getting a used PCB and take the parts was plan B if I do not get the right spare parts.

As this is the third spare fob, it doesn't hurt that it won't work, but I just thought I give it a try reparing it.

Thanks for your offer, but that shipping could be very high as I live in Europe.
But I may come back to you.

Currently I replaced it with a small capacitor and odered a new battery. Let's see if it does something

 

Below are 5 videos related to your problem. The first of the five is the video on swapping your immobilizer chip onto a used matching PCB (not PCP! :P).

 

Dr. Bruce from MINI Key Hospital here, not sure why I didn't see this thread earlier especially since I was quoted. Regardless, I will weigh in on the OP's problem and the youtube shorts for anybody's future reference.

Regarding the OP's problem, it was highly unlikely that capacitor had anything to do with the 'no start' condition although it's not impossible. I have repaired several owner-opened keys (never a good idea) that still worked to start the car even though that capacitor was missing. The anti-theft/immobilizer system in these keys is likely very simple as it is activated by a signal sent out by the car and does not draw power from the internal key battery. As far as I have been able to determine, the components involved are the copper coil and small capacitor on the bottom side of the board and the immobilizer section of the large integrated circuit on the top side of the board. The rest of the components are likely related to the remote control functions.

These keys are manufactured by the German company Marquardt. While I'm sure many of their products are top notch, this key fails frequently and in ways that are unexpected. Parhaps it's unreasonable to put the blame soley on Marquardt as the problems stem from the main integrated circuit on the board. This 28 pin IC can fail in two separate ways- first, the immobilizer part of the IC can simply fail and become essentially an open circuit. The symptom when this happens is that the key is no longer recognized by the car. There's no fix for this as this IC is not available separately and even if it were, it's likely that it would need to be programmed to send out a signal that a MINI would recognize. The second way that these can fail is to introduce a parasitic drain in the key that will drain down even a new battery sometimes overnight, sometimes over the course of a week or so. Again, I have traced this problem to a failure or a short of some type within this chip.

If your key has failed in either of these ways the only solution is to get a new key. And the only way to diagose this is with a piece of test equipment called a Transponder Tester. It would be an inexpensive (under $100) and useful tool for anybody who works on the second generation models with regularity. If the key doesn't light up the tester, start with trying a new key and this will usually fix the problem if the key would otherwise start.

Regarding the youtube videos-

1- not exactly sure what's going on here. The car doesn't seem to recognize the key although it's mentioned that the key slot has also been damaged. While it's certainly possible to move that 28 pin IC over to an otherwise functioning circuit board (and I have done that with the 8 pin immobilizer on a three button MINI key) moving an IC with that many pins requires some very advanced soldering skills or a SMD rework station. And it requires that the original chip be fully functioning. Can't fully explain this repair as it seems that the original IC was not allowing the car to start.
I suppose the ultimate way to determine if the problem is with the circuit board or the chip is to move a chip that has either of the two common problems to a known good board and see if the problem follows. My prediction is that the problem would follow; if I ever get into SMD reworking I will try this.

2- Yes, these keys can go bad with little or no warning.

3- Bad slot or bad key, not sure which.

4- This is a previously opened key in an aftermarket shell, OEM shells are not that easy to open which is why I recommend against it. I suppose re-soldering the coil to the circuit board could work to repair the no-start condition but I have never seen a bad connection here. Perhaps the key was dropped and those solder connections cracked open.

5- Perhaps the cable was disconnected at the slot- that could also cause a no-start condition.

 

@valvashon
Thank you for your detailed response! I think you are right that this capacitor has nothing to do with the "no-start" problem.

I did not continue to work on this key for over a year now, but I did some additional tests back then.

I regonized a damaged resitor array which I replaced (near the 28 pin IC), but that also did not help.
Unfortunately, I do no have a Transponder Tester (yet), so I could not test it with that. What I did: I measured the signals on the coil with an oscilloscope while the key was in the car.
I saw a carrier frequency and some modulation on it, but could not say if that's the signal from the car or the key.
The car did not recognize anything if the key was put in.

I am afraid the main IC is dead and I have little hope that it could be replaced. As you said, it would be quite impossible to get that firmware running on that chip.

Nevertheless, thank you for your detailed explaination.