My cooling fan won't come on even when the temperature gauge is at the midpoint. If I disconnect the temperature sending unit the fan will come on but I also get a throttle body warning light. If I reconnect the sending unit the fan stays on but when I turn the jeep off and turn it back on I have the same problem the fan won't come on but the warning light does go away. I replaced the relay in the fuse box and I've put a new relay by the driver's side headlight but neither of those things helped. Does the temperature sending unit serve additional purposes other than just the temperature reading could that be my problem.