My cat 420f died the other day and now it will start but as soon as you let go of the key it dies. If you hold the key in the start position it will stay running, but if you let off the key to the run position it immediately dies.
Had this exact problem on a 432e. Start with the fuses. Had a wiring short in the loom on the rhs near the starter motor IIRC.
If you supply a VIN, hopefully one of the brilliant people on here will be able to supply a wiring schematic.
There is a service bulletin regarding that. I’m not able to access it at the moment.
CAT0420ECKMW01189 turns out its our E model not F, I'm not sure how different they are.
You rang....?? To the OP. Check your messages. A schematic is in your inbox.