Could it be the key

Hey Folks:

This is really a starting question but I am out of ideas as to where else to look. My 07 Tacoma has 120,000 miles with an automatic transmission. Sometimes the truck starts and sometimes it doesn't. The battery is strong, I put in a new ignition switch, starter relay, brake switch, transmission range sensor, and a very expensive new starter (that I didn't need) that my local Toyota dealership put in. The truck still is will not start on occasion. All of the lights, horn, radio, etc work but the starter will not attempt to turn. Sometimes when I turn the key there is a delay of a few seconds before the starter turns over. I'm out of ideas. Can the key be defective in that it can't tell the computer that IT is the proper key for this truck? Can the key code be off? It is not a Smart Key, but I did have to have it mated to the computer by my local lock smith a few years ago. Any ideas?

 

I believe the security system cuts fuel so you'll get a crank but no start with the wrong or a damaged key. The security light will also be flashing.
I'm thinking you have a loose or corroded battery connection somewhere.

 

That is correct.
The security system cuts fuel and spark.
But it doesn’t stop the starter from spinning.
You can crank the starter until the battery goes dead.

I’d suggest taking a look at this post.
https://www.tacomaworld.com/threads/2nd-gen-information-diagnostics.784008/#post-28042155

 

Hey Guys:

Thanks for the prompt replies. I forgot to mention that the truck SEEMS to start more reliably when the engine is at the ambient temperature but, most of the time I turn the key and ....no starter. Everything else works that I know of but.....no starter.

 

I’d start by checking the chassis grounds first.

 

Hey Guys:

Just found out that I can start the truck when the truck is in P or N , my foot is on the brake and my wife manually operates the contacts on the starter relay. I guess that power is not making it to the relay. I can't find a wiring diagram for the starter circuit but does anybody know what is upstream of the relay that might be the trouble?

Thanks, Bob

 

Try this one. I hope it helps

 

Upstream is the ignition switch.
Upstream of the ignition switch is the 30A AM2 fuse.
But you really need to diagnose what is missing.
Jumping the relay doesn’t diagnose the problem.
It just bypasses the problem.

You need to test the appropriate relay contacts in the fuse box.

I still think you should see the link I posted above.
Under the starting system diag section, click the spoiler button.
All the information is in there.
Should you have any questions after reading it, @Dm93 and myself would be happy to help.
After all Dm93 did an excellent job in the link above.

 

Here's the Starting System Diagram for 07.
You have 2 separate inputs from the Ignition Switch, one goes direct to Pin 5 of the Starter Relay and the other goes through the Park/Neutral switch and then to Pin 1 of the Starter Relay.
Pin 2 of the Starter Relay is constant Ground and Pin 3 of the relay goes to the starter S terminal.

 

Hey DM:

Thank you for passing along the ignition wiring diagram for my 07 Tacoma. I have referred to it countless times trying to figure out my starting problem. I believe that I have narrowed my problem down to the fact that it seems as tho the G/Black wire coming from the ignition switch is not always powered. The diagram does not show something in the line from the IG switch to the relay but, something is blocking the IG from sending voltage to the relay. Do you know if there is something fuel line related that could be doing it? I think that I hear the rubber fuel line at the engine being charged when the truck won't start.
This problem has been exasperating. At times the truck starts right up.........a minute later....nothing. The fuses are good, the battery strong, I've put in a new ignition switch, starter, relay, and P/N switch. I can always start the truck by manually operating the relay, but at times, the truck will not do that itself. Any revelations?

Bob

 

So your saying Pin 5 of the STA Relay doesn't have power when cranking sometimes?
There isn't anything in the factory wiring between Pin 7 of the ignition switch and Pin 5 of the starter relay, have you checked power at Pin 7 of the ignition switch and at Pin 5 of the starter relay when it won't start?

Anything aftermarket (remote start/alarm/car lot kill switch) tapped in that you can see?

 

Hey Deegoe:

I read with some interest a post from Oldeguido back in April about a starter situation very similar to mine. I'm still struggling with my own problem and will do some more testing once the rain stops ( 6 days straight now). In the meantime, I do not think that my truck has any aftermarket security features but, I bought the truck used 12 years ago and maybe there IS something there. If so, where should I start looking for it? Also, you asked me to find any voltage at pin 7 of the Ignition Switch. Any diagrams to tell me how to locate it?

With much thanks, Bob

 

It's the Green/Black wire at the ignition switch, if you don't have power there while cranking you need to check Pin 3 (White/Red). If you do have power on Pin 7 (Green/Black) then you need to find where it is broken between the switch and starter relay.

 

Hey Guys:

The saga of my starting woes continues BUT, with a few surprises. The green/black wire at the ignition switch has power but does not make it to pin 5 of the starter relay. Something is interrupting the flow of voltage. It turns out that upon close scrutiny my 07 indeed has an aftermarket security system in place. It seems as tho that system gets its power from the outside mirror circuit. I also found the after market wires going to the horn and several lights.
I would like to disable that system but it would help if I knew what I was looking for to do it. There has to be a sending unit of sorts in there and I expect it to be linked in to the green/black wire between the Ignition Switch and the Starter Relay. I am not, nor have I ever been, a contortionist but I will do whatever I have to. Would the ?Sending Unit? be a module of some sort, how big and possibly ...where.


Bob

Post Scribum: You'll have been invaluable thru this endeavor. I'll add my two cents to other members concerns when I feel competent to do so.

 

Just follow the aftermarket wiring until you find the alarm unit, they are usually a black box about the size of a deck of cards or slightly bigger. Most of the ones I've seen aren't very far from the steering column or are stashed behind the kick panel.
Most are pretty easy to remove, just take out all the T-Taps, remove all the aftermarket wiring, and repair any wires they cut or spliced into.

 

I'm still wrestling with my starting troubles but in searching for the alarm module I found a few unconnected male clips that are just part of the wiring harness behind the cover by the driver's left foot. Question is: Does Toyota use the same wiring harness on all models of the Tacoma? Are those unconnected clips there for options that my Base Model does not have?
I absolutely cannot find the alarm module for the security system on my truck. I have torn apart the wires at the driver's side kick plate but there isn't anything large enough to qualify. I suspect that the alarm system is an "after market" but if it was installed at the factory or the dealership would the parts say Toyota on them?

Bob