Two problems related to starter relay have been reported for the 2008 Jeep Wrangler. The most recently reported issues are listed below.
Intermittent problem starting the car. When the problem occurs, you turn the key and you just hear a dull click. The engine does not crank. After 2 or 3 tries, it will start. This has happened about a dozen time in the last 6 months. The starter relay switch has been changed but the problem persists. A new starter was put in but the problem continued. So far $350 has been spent but nothing has been resolved.
About 18 months ago was 1st incident - inserted key, motor clicked but would not turn over, 2nd try worked. This same thing would happen every couple months or so then started taking 3-4 trys before turning over. In last 2 weeks it was been more frequent 2-3 times per week. Today it was at least 10 times - finally I shifted to neutral and back into park then it turned over. I've googled to see if others experiencing same, seems it's a common prblem. Some say it's a problem with shifter not being all the way in park, others say it's "by a ground offset that causes the pcm to turn off the starter relay control circuit do to the double start override feature or a trs input state not valid. If the concern is gone, then add a 8 gauge or larger wire between engine and battery negative, from body to engine, and engine to trans bell housing to tie the grounds together. It is recommend to check the existing grounds and cables on the engine and for the pcm. If there is a bolt or stud, remove it and check to make sure they are clean and corrosion/rust free. Clean the effected areas and the threads if needed. Check the trs connector for signs of moisture or corrosion and clean connections". This really needs to be looked into!.