Toyota Tacoma Forum banner

1 - 20 of 49 Posts

·
Premium Member
Joined
·
2,662 Posts
Discussion Starter #1
Is there a list or diagram of all the electrical ground wires? I had a weird problem where the truck wouldn't start unless the OBDII code scanner was plugged in!
I searched around on other forums and I guess the scanner acts as a ground for the ECU. So I need to figure out what ground wires I forgot to reconnect...

Anyone know if there is such a diagram or list?? :shrug:
 

·
Registered
Joined
·
758 Posts
There is a "Ground Points" section in the Factory Wiring Diagrams. The ECM grounds on the intake manifold near the TB (brown wires on a ring terminal), You may have left this loose when installing your FF intake. If no one else posts it, you can PM me your E-mail address and I'll scan for you
 

·
Mambeau / Admin
Joined
·
47,553 Posts
Here's a 1999 diagram illustrating what components ground to which ground points. The locations of the ground points are given in the table at the end of the document.
 

Attachments

·
Premium Member
Joined
·
2,662 Posts
Discussion Starter #5 (Edited by Moderator)
So I am still having the same problems. But I may have it narrowed down. I have had a couple codes concerning the o2 sensor bank 1 and sensor 2... and ignition... since my truck wont start with the code reader plugged in... and will shut off if its unplugged.

So I think it may correlate to the ground on this picture posted. It says that this ground is located Near the Throttle Body. Does anyone know where this ground is? Explanation or picture would be awesome. I can't seem to be able to find a ground that needs grounding.

I think that this issue may be correlated to a few other issues I am having. So I would greatly appreciate some input. Thanks

Another question on a side note. Are there any grounds on the intake manifold? And would it affect the ground if mine is powdercoated?
Thanks again


 

Attachments

·
Mambeau / Admin
Joined
·
47,553 Posts
Here (attached) is a diagram illustrating the location of ground point EB on a 1999 4-cylinder Taco.
 

Attachments

·
Registered
Joined
·
3,710 Posts
Anybody know if the powdercoating on the intake would affect the groudability...(if thats a word)
yes, im pretty sure powder coat is not a good conductor...either scrape it off for the ground, or find another ground source
 

·
Mambeau / Admin
Joined
·
47,553 Posts
If you're going to have to go to the trouble of establishing a new ground point, you might as well make it a solid one.

I'd put it on the block or run a line directly to the frame.
 

·
Registered
Joined
·
3,710 Posts
If you're going to have to go to the trouble of establishing a new ground point, you might as well make it a solid one.

I'd put it on the block or run a line directly to the frame.
i was going to say that those were the two best options
 

·
Premium Member
Joined
·
2,662 Posts
Discussion Starter #13
Ok my truck still won't start without my scanner plugged in!
I checked the grounds in the engine bay, and I added a new ground from the block to the frame.

Any other ideas?
Are there other ground points for the ecu that aren't in the engine bay?
Thanks
 

·
Mambeau / Admin
Joined
·
47,553 Posts
Josh:

I've emailed you the 1999 2RZ engine control wiring diagram.

Take a look at the way the circuit opening relay's ground line ties into the ground line from the OBD port to the ground point. The two ground lines connect at connection point 3A, which is somewhere around the Cowl Wire / Junction Block connection behind the left dash.

I can't figure out exactly how such a glitch might work, but ... If the circuit opening relay can't ground until the scanner's plugged in, you shouldn't be able to start the engine at all.
 

·
Premium Member
Joined
·
2,662 Posts
Discussion Starter #15 (Edited)
Josh:

I've emailed you the 1999 2RZ engine control wiring diagram.

Take a look at the way the circuit opening relay's ground line ties into the ground line from the OBD port to the ground point. The two ground lines connect at connection point 3A, which is somewhere around the Cowl Wire / Junction Block connection behind the left dash.

I can't figure out exactly how such a glitch might work, but ... If the circuit opening relay can't ground until the scanner's plugged in, you shouldn't be able to start the engine at all.
I've covered every inch of that circuit and can't find anything wrong. Does anyone have any idea what could possibly be causing this? Is there somewhere I could add a ground wire to possibly help fix the problem?

According to this pic from the FSM the data connector port has a ground (IE), can I just tap into that ground and run a new one? Would that help anything?
 

Attachments

·
Mambeau / Admin
Joined
·
47,553 Posts
Ground point IE is where the DLC3 is supposed to reach ground. The fact that something has to be plugged into the DLC3 connector for the engine to start may or may not mean the line onward to ground point IE is the problem.

It might mean there's a short or fault in the DLC3 connector itself.

I'd run a temporary test wire from the circuit opening relay to ground point IE (or any other good ground point) to see if the engine will start. If it does, that narrows the problem down to the circuit opening relay circuit.
 

·
Premium Member
Joined
·
2,662 Posts
Discussion Starter #17 (Edited)
Ground point IE is where the DLC3 is supposed to reach ground. The fact that something has to be plugged into the DLC3 connector for the engine to start may or may not mean the line onward to ground point IE is the problem.

It might mean there's a short or fault in the DLC3 connector itself.

I'd run a temporary test wire from the circuit opening relay to ground point IE (or any other good ground point) to see if the engine will start. If it does, that narrows the problem down to the circuit opening relay circuit.
could any of this be affected from when I had my head unit and security system put in?

Also wondering if one of the ground wire kits would benefit me at all... Ive always had weak electrical problems with this truck. Dim gauges.. dim lights.
 

·
Mambeau / Admin
Joined
·
47,553 Posts
could any of this be affected from when I had my head unit and security system put in?
Yes - it's possible. However, I have no way to address that possibility without knowing exactly how the head unit and security system were installed.


Also wondering if one of the ground wire kits would benefit me at all... Ive always had weak electrical problems with this truck. Dim gauges.. dim lights.
It's conceivable that the current starting issue is related to a more general wiring or electrical problem. However, if the starting problem arose after you were already having issues with dimming, it's unlikely the more general issue is the immediate cause.

Run a temporary ground for the circuit opening relay and see if that helps.
 

·
Premium Member
Joined
·
2,662 Posts
Discussion Starter #19 (Edited)
Yes - it's possible. However, I have no way to address that possibility without knowing exactly how the head unit and security system were installed.




It's conceivable that the current starting issue is related to a more general wiring or electrical problem. However, if the starting problem arose after you were already having issues with dimming, it's unlikely the more general issue is the immediate cause.

Run a temporary ground for the circuit opening relay and see if that helps.
Ya probably true, it only started when I put the turbo on anyways. So its something to do with that I'm guessing.

Forgive my ignorance, but how do I run a temporary circuit. Just run a wire in the same place of the regular wire circuit opening wire (white with black stripe) and run it to ground... Is that correct?
 

·
Premium Member
Joined
·
2,662 Posts
I can't figure out where the Circuit opening relay is... any help?

1st pic is of the OBD hookup, I followed the ground wire the best I could and I ended at this recepticle (picture 2)... did I take a wrong turn somewhere? Is this supposed to be hooked up somewhere? cause it wasnt...





thanks randy... Couldn't do it without ya!
 

Attachments

1 - 20 of 49 Posts
Top