The year of the Jeep: 2001 XJ. 128,000 miles. Have had about 10 years with no issues. Daughter uses it for daily driver.

The issue - recently changed the crank position sensor (vehicle would not start). Ran great for about a month with no issues. Also replaced battery at this time since original was 5 years old.

Now - the Jeep is having some crazy issues. Starts right up. After about 20 minutes or so of driving, engine light will come on (flash off and on) as well as the "check gages" light, speedometer will go whack (will peg multiple times), and engine rpms go through the roof (engine revs without gas pedal movement).

Checked battery for ground issue and couldn't find anything wrong. Check engine light doesn't stay on so there's no code for me to read. Help!!!

 

What brand crank position sensor did you use? The only ones I trust are MOPAR (if you can find it) or Echlin from NAPA.
I also just had an issue where the speedo would bounce up, check gauges would come on and voltage gauge would get whacked out. Turned out to be the alternator. Replaced that and all was good again.