Hi, wondering if anyone has experienced a dead starter circuit on the JK. It has no faults being recorded on the OBD reader, so i am sure it isnt computer, but more a breakdown between ignition switch and start solenoid. I have gone to the start relay and have power on input 30 however when connecting this direct to terminal 87 nothing happens - i would have thought it should at crank or at least draw power if the solenoid is stuck/RS. Everything else is fine, just on the start circuit absolutely nothing happens - and the voltage doesn't drop, so there is no draw either. This is a Right Hand Drive vehicle (Australia), so position of relay box ect may vary from the USA, but i am sure the electrics are common
The ignition switch sends a signal to the wireless control module. the WCM send a "crank" request signal to the TIPM to tell it to run the starter.
The PCM sends a signal to the TIPM to tell it if its in park/neutral or if the clutch is depressed in a manual.
If the TIPM see's a start request and a P/N signal it will apply power to pin 85 of the starter relay.
pin 86 will be grounded by either the PCM P/N wire or the TIPM.
Power to the relay comes from Fuse J17 (40A) on pin 30.
Output from the relay is on pin 87 and goes to the starter
if you put 12 volts on PIN 87 and the starter doesn't turn over then you either have a bad starter, bad battery feed to the main starter lug or a bad Yellow/Grey wire from the TIPM.
At the starter you should have a good battery feed on the big red wire.
you can put 12 volts on the yellow/grey wire at the starter and test it there.