P38A intermittent locking/unlocking

kermit_rr said:

Hi all
Sometimes I go to lock the car and the red light on the fob lights up, but the car doesn't respond. If I press unlock followed by lock, the car will respond both times.
I do have the antenna unplugged, but this doesn't appear to make any difference. Could this be a dodgy fob that lights up but doesn't transmit?
I was going to buy a 2nd fob as I only have one, but then we went into lockdown. If theres a car problem, then I'd rather fix it first before spending on another fob, but on the other hand, if the fob is dodgy then I'd rather get a 2nd fob and keep the old one as a backup
cheers

Click to expand...

kermit_rr said:

thanks, i did wonder, i've put new batteries in. maybe i should leave the antenna connected for a few days, see if i notice a difference longer term

Click to expand...

kermit_rr said:

I don't have the 'key in ignition' message. I can stand at the back wheel and keep pressing lock all day with no joy, as soon as I press unlock then the lock action jumps into life.
If i didn't know any better, its as though unlocking wakes the system up. I know thats complete rubbish, but just how it appears

Click to expand...

Datatek said:

Door lock micro switches, it will not lock if it thinks it's already locked, pressing unlock gives the mechanism a bump. That's my theory,.

Click to expand...

martyuk said:

Mine does it aswell sometimes... I replaced the door latch a few years ago with a brand new one (before I got into refurbishing them!) and I've also got upgraded receiver, so I don't get battery drain, and also have the antenna plugged in.

It seems to do it randomly to me too. I wonder if it is a bit of RF interference that is causing the key fob transmission to be garbled by something else - it wouldn't necessarily explain why an unlock press and then a re-lock press would fix it though. I also sometimes get it with mine too where unlocking it takes a couple of presses to make it receive the signal and unlock it.

The thing with the later RF receiver, and the fob filter that we make is that it won't STOP RF interference from being received by the vehicle - it will just stop that from being passed onto the BECM and waking it up. They only pass on a valid P38 key fob, so if there is corruption in the data stream, be it from a low battery, so the transmission isn't as powerful as it should be, or interference which messes with what the RF receiver sees - then you would get the kind of thing where it might not lock/unlock.

I'm only surmising though - without having a radio frequency analyser to see what is actually in the air on the frequency of the fob and watching it whilst you are trying to lock an unlock to see if there's any correlation in it, then it's all guesswork. I've put it down on mine to one of the P38's anomalies...

As an aside, mine also did it with a new key fob from LR aswell as my original one.

Click to expand...