C5 Immobilizer (NOT) Faulty - Radio Interference.

[David Goddard]

Do you know that in 1998, the AA and RAC were called out to 8,800 breakdowns where cars failed to start - reason the immobilizer transponder was swamped by a nearby radio transmitter?
My C5 came up with an "Immobilizer Faulty" message when I returned to a car park and tried to start the car last Sunday. The RAC were with us in 5 minutes (advert!). He had a Syke Pickavent Key checker box in the back of his van. A warning light was flashing which indicated "someone" was transmitting near to the car park. Usual solution is - tow the car a distance away! In my case he spotted the light going out and shouted, "Quick, start the engine!" - it did.
Checking the Internet, I see that most cars transponders are on 433.92MHz. The new police TETRA band is either side of this frequency. OFCOM have checked these transmitters and found they transmit within their allocated band. The problem is the receivers in cars are not of the same quality. They are not particularly selective so the unwanted transmission bleeds in and overpowers the rather tiny transponder signal. I also find that 433MHz is in the middle of the Ham Radio 20cm band - great.
Mobile Phones are on a much higher frequency so they have no effect.
Moral - don't assume the ECU has failed if a car won't start. (a) Have a tow rope in the car and have someone tow you a couple of hundred metres away. (b) don't park under TETRA towers (no, I don't know what they look like!) (c) have a walk round to see if someone is in another car with a transmitter (d) apparently screening the key with your hands can help a bit.

[np]

I remember seeing this on BBC`s Watchdog a couple of years ago.A particular town was badly affected.I think L/Rover Freelanders were worse affected,& the ecu was blamed at the time,untill w/dog got on the case.
I wonder how many people have has this,& had a bill for a new ecu?!!