Our Focus (2001) has developed an intermittent fault in that it won't
start on occasions which seem to be when the ambient temperature (not
the engine!) is very hot. The PATS LED which is flashing slowly as
normal when you get in goes out when the key is turned rather than
coming on for about three seconds. Everything is completely dead. After
a while, which may be 5 mins to an hour or more, it does start, which I
guess is when the car has cooled down.

It would appear that either the transceiver is not reading the code
from the key or, if it is, the immobiliser is not getting the go ahead
to allow the engine to start. It happens with both keys so I guess it
rules them out.

We've had it in a main dealers who did a diagnostics check and, I guess
as a result of that, replace the transceiver. A week later, on the
first really hot day since then, the fault has re-occured.

Two questions:
Firstly, has anyone come across this fault before?

Secondly, I can imagine the bill will start to increase, particularly
if the PATS system needs replacing, etc. If this is the case, can I
just have the immobiliser bypassed? I realise this reduces the security
of the vehicle but I guess I could just wire up a flashing LED to make
it look like its on as a deterrant - and there may be insurance
implications.

Cheers,
Pete

"pete"  wrote in message
news:1121078742.776196.155860@f14g2000cwb.googlegroups.com...

> Our Focus (2001) has developed an intermittent fault in that it won't
> start on occasions which seem to be when the ambient temperature (not
> the engine!) is very hot. The PATS LED which is flashing slowly as
> normal when you get in goes out when the key is turned rather than
> coming on for about three seconds. Everything is completely dead. After
> a while, which may be 5 mins to an hour or more, it does start, which I
> guess is when the car has cooled down.
>
> It would appear that either the transceiver is not reading the code
> from the key or, if it is, the immobiliser is not getting the go ahead
> to allow the engine to start. It happens with both keys so I guess it
> rules them out.
>
> We've had it in a main dealers who did a diagnostics check and, I guess
> as a result of that, replace the transceiver. A week later, on the
> first really hot day since then, the fault has re-occured.
>
> Two questions:
> Firstly, has anyone come across this fault before?
>
> Secondly, I can imagine the bill will start to increase, particularly
> if the PATS system needs replacing, etc. If this is the case, can I
> just have the immobiliser bypassed? I realise this reduces the security
> of the vehicle but I guess I could just wire up a flashing LED to make
> it look like its on as a deterrant - and there may be insurance
> implications.


Firstly as the PATS warning lamp (if i read correctly) is going out when you
power up the ignition (from it flashing slowly- i.e. immobilized state) and
NOT flashing quickly, then the ECU is reading the code from the key fine.
This rules out problems with the ECU, the transceiver and the key.

When you say its dead- do the dash lights come on? I am assuming they do,
but you have no starter action when you turn to position II. ?

If you have NO dash lights, then you have a break in the wire from battery >
engine bay fuse box > main fuse > ignition relay > ignition switch which
should be fairly easy to determine. Most likely its one of the main relays
with a dry joint which is opening up in hot weather.

Check the earth straps whilst you're at it.

If the ECU failed to receive a code, or an inncorrect code from the key,
then the PATS light would be flashing quickly.

Tim..

Thanks for the reply Tim.

When the car is working normally, the PATS warning LED goes from slow
flashing to a steady light for about 3 seconds when the key is turned
and then goes out.

In the fault condition, the slowly flashing LED goes out when the key
is turned and remains off (there is no rapid flashing which, as you
pointed out, would indicate that the code is incorrect). Also, in the
fault condition, the dash lights do come on but there is no starter
action.

Any further thoughts?

Thanks for the reply Tim.

When the car is working normally, the PATS warning LED goes from slow
flashing to a steady light for about 3 seconds when the key is turned
and then goes out.

In the fault condition, the slowly flashing LED goes out when the key
is turned and remains off (there is no rapid flashing which, as you
pointed out, would indicate that the code is incorrect). Also, in the
fault condition, the dash lights do come on but there is no starter
action.

Thanks for the reply Tim.

When the car is working normally, the PATS warning LED goes from slow
flashing to a steady light for about 3 seconds when the key is turned
and then goes out.

In the fault condition, the slowly flashing LED goes out when the key
is turned and remains off (there is no rapid flashing which, as you
pointed out, would indicate that the code is incorrect). Also, in the
fault condition, the dash lights do come on but there is no starter
action.