The Battery
Today's vehicles place a heavy load on the battery. They have a constant drain on them by PCMs with keep-alive memories, radio memories and other such devices with adaptive learning strategies. This makes clean, corrosion free battery terminals very important. Even a slight corrosion film on a top or side post battery terminal can cause a memory to be lost or cause a charging problem.

On a top post battery, remove the terminal and with a wire brush clean the post until it is just shiny and scratchy. Do the same to the battery terminal on the cable end. If the battery post is too far gone, you will need to replace the battery. If the battery cable terminal is too far gone, you can get a replacement battery cable. Yeah, I know they sell replacement terminals, but I only use them as a last resort. Most times they only allow a corrosion problem to return with a vengeance.

On a side post battery wire brush the face of the battery and cable terminal until it is shiny, scratchy clean. When you reattach the terminals make sure it goes on straight and not cross-threaded. Also don't tighten the terminals too tight. You will rip the connections inside the battery apart. There is a reason why that big terminal has such a small hex head on it.

Then wash the battery and keep it clean. Dirt and oil on the top of the battery will cause a parasitic drain that reduces battery life. When everything is clean and tight, a coating of white lithium grease or spray battery terminal protector will keep the terminals from corroding again. If you have a can of spray paint in the garage, use that. The idea is to keep air from getting to the lead. Don't forget to get the underside of the terminal, between the terminal and the battery.