Do I need a new PCM
Hey guys, so I started having an electrical issue with my Sept 08-build JK V6 petrol 2-door manual (161K km's) out of the blue this week that I assume to be a PCM issue, however I thought I'd consult with the brains trust here just in case I'm missing something obvious before I bite the bullet and go & fork out big bucks for a new computer.
Symptoms are: After standing for a while with the engine off & the key removed from the ignition, doors will lock/unlock with the key fob & headlights switch on as per usual upon unlocking. However, when you open the door & sit behind the wheel the electrical system appears dead (ie: it hasn't woken up from it's "sleep" when everything shuts down after a period when you turn it off and remove the key). No interior light or odometer readout upon opening the door, and when you insert the key into the ignition and turn it through the clicks nothing happens either (no lights, chimes or electrical whirrs under the bonnet from fuel pumps, throttle body etc) until you advance all the way through to the engine turnover.
Engine will then start up and run normally, however dash display/instrument cluster is still dead with no lights/gauges and no functioning switches (indicators, ventilation fan, headlights etc); the windscreen wipers do however then turn on all by themselves and run at the constant slow setting. Disconnecting the negative lead on the battery (either momentarily or for a long time to discharge the capacitors) will rectify the issue immediately and the Jeep will run & function flawlessly until the next sustained shutdown.
The only red herring in all of this is to do with the radio/nav head unit (it's the 10yo factory option one with the touch screen and built in nav & hard drive). While as I mentioned earlier that everything else electrical is dead in the cabin upon opening the door, the unit's backlighting around the menu switches is on. Another gremlin to do with the unit (that has functioned flawlessly for 10 years too) is that it wouldn't eject a CD the other day and appeared to freeze-up momentarily after the screen pivoted down to expose the CD slot, before then closing the screen back up again and resuming normal function; CD ejection functioned as normal on my next attempt.
The only reason I mentioned the head unit issued is that it does connect to the main power BUS & communicate with the PCM; I'm wondering if an issue with the radio head unit could be causing the broader PCM electrical issues with the vehicle? Any input is appreciated guys!
PS: I did check for any fault codes thrown via the dash & nothing showed up.
Cheers!
Last edited by jklad; 15-12-2018 at 11:44 AM.
|