I know this has been the topic of previous threads but I'm not sure there has been a definitive solution.
I've owned my TH for two and a half years and it started to play up after a few months.

The car will fire and run for a second then it shuts down, usually about three times before it will start and keep running.
The problem is intermittant and sometimes gets worse to the point where it affects every start but then it goes away for a week or maybe a few months.

You can hear a relay click from behind the ashtray as it shuts down. ecu?
The cut only seems to last 1-2 secs. then it resets.
Sometimes if I can give the motor a bit of a rev before it shuts down the inertia will keep the motor revving through the cut and if it still has sufficient revs after the cut resets then the motor will keep running.

In my case I don't think the cause is battery related because a new battery didn't fix it.

The BCM appears to have been replaced once under warranty as it has an 02 build date so the previous owner may have been chasing this problem before I bought the car.

I took it to my mechanic and he plugged in a scanner to read the fault codes
The ecu read code 54. immobiliser comm.
The bcm read codes 12. ID unequal, 11. TP read fail
He said the immobiliser communication code meant the immobiliser wasn't sending the right signal to to ecu so it was shutting down and he thought the bcm codes meant the proximity sensor was having trouble reading the chip in the key.
Last thing friday afternoon he didn't have time to investigate further but said if I had a spare key I could try that because sometimes the chip for the proximity sensor in the key can break.

My spare key didn't fix the problem.

Does anyone have further info on the meaning of the codes?

Needs a new battery that's all, extremely common issue.

Edit: Just noticed you said you've got a new battery, might be the immobiliser issue then, or even the alternator if its playing games. Have you had all that stuff checked out?

Only things I know to do with the Immobiliser problems is to clean out the loom to the BEM, and double check all the wiring is secure.

as lugo said it might be the wire from the ecu to the bem, i think its to the bem :confused:
pretty sure its a brown wire
if you can hear a relay clicking them it might be the fuel pump relay, if the immoboliser isnt deactorvating then the fuel pump wont work
could also be a faulty battery, even tho its new doesnt mean its a dud. i had a new one last a week!
may be the alternator to, cause if the voltage drops too low the ECU cuts out everything

http://martybugs.net/articles/magna-stall.cgi

Explains the POSSIBLE cause in detail

Steve

http://martybugs.net/articles/magna-stall.cgi

Explains the POSSIBLE cause in detail

Steve
Exatly how i fixed the issue in my Rada as well

Yeah I've read that thread and tried refitting the plug with the brown wire.
It's hard to tell if it worked at all. It seemed to work the first time but the problem returned the next day.
I tried it again and it did nothing.

In the Martybugs thread it mentioned soldering.
Do they mean soldering wires directly to the BEM circuit board?

The bem fault codes 12. ID unequal 11.TP read fail might indicate a problem reading the key.

Anyone know more about the codes?

Ok this appears to be fixed.

I unplugged the key reader sensor
This caused the problem to be present 100% of the time.

I gave the pins in the connector a slight twist so they made better contact and plugged the reader back in.

No reoccurrence of the problem so far.