Originally Posted by gamefreakgc

Yes, there's a block to firewall in the back as well as as the plenum on the driver's side for the diagnostic port (this one gets dirty due to being removed for repairs). There is also your battery ground on the fender which is the most important, this one helps the most. For starting, the lower engine harness that goes from the battery to the starter on the passenger's side has a ground that attaches to the bottom of the block. This one gets real grimy and oily over time and could cause starting issues as well. I think it may be a double ground though since I think it also grounds to the battery cable to fender.

There's also an ECU ground inside the cabin but unless you dunked your 4Runner in a lake this one should be clean.