I recently bought a 2003 Jeep Grand Cherokee and it had quite a bit of negative battery post corrosion and the terminal connector was splitting apart. Last night I took the old connector off, cleaned the battery posts (both) with battery cleaner, used a batter post brush and cleaned both posts and the positive cable connector (which is in great shape). After putting it together, tightening everything down and spraying some battery protectant on it, it decides not to start. I put my multimeter on it and its giving me about 13.80 volts. I've taken the negative connector off, cleaned the bare wires again made sure that the clamp was tight on the wires and tightened everything down again. I've done this numerous times on other vehicles without any issue - it's pretty straight forward DiY. Any ideas? Why would the Jeep start with all that corrosion and bad clamp, and not start after the cleanup and repair? Thank you for your help!
It may have a theft deterrent system that was activated when the battery was disconnected. Try locking the doors and opening then from the driver's door with the key. If that door doesn't work, try the same thing with the tail gate.