I have a 2000 Grand Cherokee 4.0L 6 and am having some strange electrical problems. My Jeep has gone crazy! without warning the ABS light and brake light will come on, along with the check engine display. The speedometer will jump from 0 to 80mph, while maintainin a 35mph speed the lights will dim and the heater fan will go on and off. There also seems to be a skip in the engine when this happens. My mechanic said nothing showed up on the diagnostic, but did replace some corroded wires. This did not help. This problem comes and goes.

Any suggestions what to look for?

Thanks, Mike

I would look at your alternator. Check the connectios to it and the regulator. Also look at your ground wires, makesure that there clean and tight.

I have a 99 grand cherokee, it acted similar about a year ago. I took it in and my mechanic cleaned the inside contacts of the battery terminals. They were clean upon visual inspection, however the corrosion we couldn't see caused the electrical systems to go nuts. good luck!