SCREENING AN ECU UNIT

Are you using the 'phone with a properly installed handsfree kit? If so what's the kit, what's the 'phone (make and model) and where is the external aerial mounted? If you're just using the 'phone by itself with no external connections, do other 'phones cause the same problems?

There's some legislation coming on the books soon that will solve your problem.

Sorry to disappoint but even that may well not do any good, it's just as likely that the interference from the mobile is finding its way in through the cabling to/from the ECU.

You can't, effective screening is not a simple bolt on retrofit.

I would agree with them. If it really is happening and is reproducible it would point to a fault in the ECU rather than lack of screening.

You could wrap it a roll of tinfoil - it still wouldn't be screened.

Where is the phone positioned when you get this problem? What frequency (network) are you on? What is the phone model? Do you have an external antenna? (although even without one I'd still not expect any interference of the sort you describe).

Mind you, VW would say that, wouldn't they? It's a bit like if you smoke

40 a day and you get lung cancer, then you phone up Imperial Tobacco and guess what, they'll act all surprised and "Can't see that happening"...

They certainly would. The radiated power from a phone is quite small and if it were to produce the effect described then the vehicle would be very susceptible to interference from other sources capable of producing equivalent field strengths within the vehicle. Several roads I can think of near radar heads would certainly be littered with dead VW's and stopping at traffic lights next to a taxi would be even more risky than usual.

There is an EMC standard for cars (I don't have a copy with me here but will find you the reference later) which more than requires sufficient RF immunity in the vehicle systems to prevent interference from a phone in a car. That said, a fault in the vehicle wiring loom or a poor contact somewhere in the wiring/ECU can allow interference in. The chances of the average garage auto electrician finding such a fault are zero and the chances of a fully equipped RF lab finding it are not much better. Simply moving wires can make it go away, only to return the second your back is turned!

Except it won't unless this legislation can miraculously change the existing ECU or phone.

Although they do say not to use your phone inside the car.

Hi Ian~

I'm just using the phone normally, without a hands free kit. I've had my friends in my car and their phones have caused the car to dip and stall too. I'm on the O2 network, my friends are mainly on T-Mobile and Orange.

Acquiesce.

The phone's normally left on the passenger seat. I'm on the O2 network, but other people's phones have caused my car to dip and stall too. I don't have an external antenna. Diagnostic checks can't find anything wrong...it's a mystery!

Acquiesce.

Cheers for your reply Peter. Two separate diagnostic checks have failed to find anything wrong with the car, although mechanics say they experienced the dipping/stalling when they took my car out for a 20 mile spin...

Acquiesce.

What happens if you put it on a rolling road with the diagnostics attached and then use your phone?

Not so, it may well be a highly frequency dependent response, in which case blanket generalisations about field strength are neither here nor there, as well you should know. In this circumstance you could park the car on top of your local TV transmitter and it suffer no ill effects, but when you turn the mobile on, kerpow. In the unfortunate situation where the RF emissions from the phone are well coupled and resonant to some element in the car electronics or wiing, then it hardly needs to be high power in order to wreak havoc, does it? It just needs to be radiating and at the right frequency.

Hah. The point is that RF immunity is not an exact science (even though some people, including a fair few of its practicioners, would dearly love to believe otherwise). It is chaotic and probabilistic in nature. EMC standards notwithstanding, because our friend's ECU is not sealed in an RF-tight box with no connections to the outside world (as this tends to render them inoperative vis a vis the engine :-), there is a small but appreciable chance that his phone is stuffing up his ECU. Anyone believing that an EMC standard 100% guarantees prevention of interference is living in a dream world IMHO.

Indeed. So much for well-defined standards.

The message from Peter Parry contains these words:

I'd have thought it would hiccough just as much idling as it would driving if it's the phone upsetting it.

That is possible, but somewhat unlikely as the interference appears to be present at both 900 and 1800MHz and the two bands are not exact harmonics. EMC effects also tend to be broadband rather than frequency specific, the frequency band affecting the method of ingress of the signal into the device more than anything else.

No, but that is an unusual case and you wouldn't have had the same effect on both 9 and 1800Mhz.

It follows the rules of physics.

VW design and build to meet the EMC standard. That standard is enough to prevent such interference. A device does not have to be in a sealed box with no connections to be immune to EMC.

In that case I spent several years in a TEMPEST dream world making sure amongst other that a standard prevented precisely that. Making something to be reliably and consistently immune to RF is not an art but just good engineering.

Standards do not cover a fault condition (usually) and certainly do not in this case. If the vehicle can be shown to be susceptible to interference from a phone on a front seat it is faulty, if it were not faulty there would be no interference. Finding the exact cause of the fault and fixing it is not the purchasers problem.

Hi,

O2 uses a different frequency range (880-915 MHz paired with 925-960 MHz) to Orange and T-Mobile (1710-1785 MHz paired with 1805-1880 MHz) so it's more likely that it's the pulsed nature of the 'phones emissions causing the problem, rather than the carrier frequency per se.

How old is your car? I wonder because the latest vehicles have electronic control units which are 'networked' together. So the engine ECU, the gearbox ECU, the ABS ECU, cruise control, ESP (electronic stability programme), traction control, etc., etc., are all interconnected. Plenty of opportunity for rogue signals to get into the wiring.

If this were my car, I'd have a go to see if I could at least localise the area where the 'phone has maximum effect on the engine misfiring. It's possible that that there may be an electronic box under the passenger seat, (I know certain Audis had ABS boxes under the rear seats) or perhaps there's wiring up the side of the transmission tunnel or somewhere else nearby?

Ultimately, I think this one will be down to VW to sort. In any case, they should be very interested as to why one of their cars has such an unusual problem and realise the need to fix it, as there could be others out there with the same fault.

Good luck and if VW come up with an answer, please post it back to this newsgroup.