Does anyone know where this ground wire should attach?

This is the firewall of my 2001 2.7L 4x4. I have a feeling it has been like this since Toyota replaced my frame seven years ago. So I don't think it is too critical.

 

Back of the engine. Right below the cam cover. Just today I looked at mine and saw a newer type ground somebody put in that same spot.

 

Mines been gone for as long as I own the Truck

 

Put it anywhere, you really can't over ground the vehicle. But I'd guess its engine ground.

 

This.

 

Speaking of ground, the grounding cable that attaches to the negative battery post to a bolt adjacent on the chassis snapped off. I have it held to the neg. battery post wire with electrical tape. Is this grounding cable important? What does it ground exactly? I know the general wiring harness of the truck has a lot of grounding points so I'm not too worried.

 

I also have an extra ground wire going from my negative battery post to somewhere under the fuse block. Previous owner must of done this. Anybody know why there are these extra ground wires? I used to have an 87 GTI and there was a kit to replace all the grounding wires with thick gauge wires. Do these pickups have grounding issues?

 

Every vehicle ever made cqn have grounding issues. It seems that the first thing to check with most problems is the grounds.

 

I actually had my intake out today and took a picture. It's a little hard to see but there is a threaded hole at the back corner of the head, just below the valve cover.

 

I believe it attaches to where the wire harness is held to the cylinder head.

The spark plugs are grounded to the cylinder head. Without this ground wire, the spark plug current needs to go through the head bolts to the block. I guess that's fine unless the other ground wire gets disconnected too.

In any case, Toyota engineered it with this extra ground wire, so it's probably important for some reason.

 

yes back of the block. Grounds the cab to the motor then motor to the battery. The hyper-sensative modules,(PCM etc) ground to the cab. While people have been getting away with it if there is any sort of resistance in the grounds there is a possibility for the PCM to not complete the drive cycle, if you have reset you CEL, due to poor ground(s). If you are wondering an ohm meter is NOT the way to check for poor grounds. I spent quite a few hours chasing crap wire and poor grounds on old Japanese vehicles... Nissans btw are the worst.

 

I've been similarly driving around without a chassis to battery ground since doing the big 3 years ago. Both of my batteries ground straight to the block.

Is this actuality disrupting the drive cycle, or is it a million to one disputing it?

 

The drive cycle is similar but different for each manufacturer and getting the smog monitors to clear can be a problem. Most of the time it can be done in a day or 2 of "normal" driving with the right conditions. When you drive hundreds of miles and they do not clear, something is wrong. It was getting to the point of ridiculousness. I kept reading about the system and finally re-read a post about where this particular Nissan grounds its o2 sensors and PCM and how to check for bad grounds... mVolt voltage drop... sure enough mine was 100 times the minimum. <20mv drop is recommended. I installed additional NEW wire grounds and within 100 yrds of driving the smog readyness all cleared. The guy who made the post on another board said that the feedback interference from a poor ground "confuses" the PCM.

How do you "know" if it is a problem, well, you dont really unless you try to pass a state inspection and they tell you your readiness monitors havent completed their drive cycle and you have not had anyone reset the CEL. Far and away the hardest monitor to clear is the evap one... that one will not run unless the fuel tank is between 1/4 and 3/4 full and the difference betweent the Air intake temp sensor and coolant temp sensor is with a few degrees of each other and there have been at least one start/run/off - cool cycle.

 

So in the case where you never have to do an emissions test, there's no way of knowing... Or would a code be thrown?

 

no, no code, the readiness indicators just are not ready. It doesnt effect anything, it is just a way for self testing to be done. Depending on the year of the vehicle and what state you are in there can be up to three readiness indicators showing not ready and still be able to get the vehicled smog tested. If you have one too many indicators showing not ready the smog guy tells you to go away and come back in a few days. If they never clear you are in smog limbo. Cant get it smogged because the indicators wont clear and cant clear the indicators because the drive cycle wasnt done "correctly".
The inexpensive OBDII units <$99 should show readiness and when I have trouble I drive around until the drive cycle is done and they clear. I never venture too far from home and park it immediatly and I am the first guy at the test station in the AM and get it smogged immediatly. I got my 1 qt per 200 miles Tacoma smogged this way. On the drive home the CEL came on ... Catalytic convertor efficiency code. This gave me time to pull the motor and get it rebuilt.

 

Ground wires may seem redundant sometimes. If not grounded, I've seen accelerator cables melt as the engine block wasn't properly grounded, and searched for it's own ground.