100 Series Intermittent Start (Key Related?)

[AdamKFarmer]

All-
One of my friends inherited a 100 series and I have been helping him get it back on the road a bit. Currently there is a strange issue with it starting. I have looked around mud and here, not really finding what I'm looking for. The situation is this, the truck ran and started fine, but all of a sudden it didn't want to start a few weeks ago. I swung by this morning to grab the valet key so that I could do some trouble shooting and low and behold it fires right up with the valet key. I grab the normal key (with buttons) and it cranks but won't turn over, switch back to valet an it starts right back up. I am thinking something to do with the immobilizer? I know you can reprogram keys, but this one started it just a few weeks ago. Could it be a weak battery? Thanks!

 

[cbmontgo]

Ih8mud has some really good threads about this. It can be the key (look for the red blinking "key" on the dash), fuel filter, EFI fuse, fuse block, weak battery, or dirty throttle body butterfly. When my wife's 100 did this, it was the little EFI fuse that needed to be replaced, even though the old one looked fine.

 

[AdamKFarmer]

Ih8mud has some really good threads about this. It can be the key (look for the red blinking "key" on the dash), fuel filter, EFI fuse, fuse block, weak battery, or dirty throttle body butterfly. When my wife's 100 did this, it was the little EFI fuse that needed to be replaced, even though the old one looked fine.

I have been looking at these! I was heading that direction with the EFI fuse actually until the valet key worked. I think that would preclude the EFI fuse issue, no?

 

[DaveInDenver]

@AxleIke I think went through an issue with the engine immobilizer on a 100 series a few years ago. Have you found these threads? As you say since the valet key works it's probably not a fuse box issue but perhaps the troubleshooting steps will give insight.

1999 100 Series Immobilizer: Continuing Issues

My brother has a 99 100 series. We've been battling this issue since he got the thing, and we thought we had it beaten. The immobilizer is going off randomly, though I believe now it may be a moisture issue. For a while it wouldn't start at all, during the major storm we had back in February...

risingsun4x4club.org

Immobilizer issue in a 100 series - Engine Bay fuse box replacement

Developed an issue with my 2000LX not starting and a flashing security light. Found on Mud a fix to bypass the 20amp fuse. Suspicion on the thread is that the EFI fuse shorts out or has a loose connection down inside the fuse box. Doesn't seem any one has tore into it and confirmed root cause...

risingsun4x4club.org

 

[cbmontgo]

I have been looking at these! I was heading that direction with the EFI fuse actually until the valet key worked. I think that would preclude the EFI fuse issue, no?

Most likely.

 

[shellb]

Same issue in my 100...I have not diagnosed yet, just took it out of active duty. Would love a resolution though so please keep us posted.

 

[AdamKFarmer]

Same issue in my 100...I have not diagnosed yet, just took it out of active duty. Would love a resolution though so please keep us posted.

With the valet key as well?

 

[shellb]

With the valet key as well?

I never made the correlation with that key specifically, but yes it did work when I used it in the past.

Most times however I was away from home and I just kept retrying it until the normal key worked. Sometimes that took days...but it always started for whatever reason.

Obviously that process can't be trusted so I changed my DD.

 

[DaveInDenver]

With the valet key as well?

Just thinking more about this. If the gray key works but not a black then I'd think it's maybe the key(s) themselves or that the ECU has lost track of them.

If you search the Interwebz you can find the procedure a locksmith would do to program a key if you still have a black one. That's the one involving all the steps, insert key, remove key, open door, close door, step on accelerator and brake simultaneous, etc. Maybe you can get the ECU to relearn.

But if only a grey key works and no black keys do still then you may be in a security mode.

The electrical difference in the two keys is that a black key is a master and can make more masters or sub keys but a grey is a sub key and copies can't be made from it. That's why Toyota recommends giving only grey keys to shops or valets, so a new key can't be made to defeat the immobilizer.

If no black keys work or can be found you need Tech Stream to make a new master key, the rub your belly, pat your head in the driver's seat procedure can't be used.

I worry about this sometimes when I unthinkingly give a black key to a shop. You can make the immobilizer forget all the keys except the one you're using and make it relearn to only recognize the one(s) you have. But this functionality I bet means there's a way to glitch the firmware and give you nuisances like this sometimes.

 

[AdamKFarmer]

Just thinking more about this. If the gray key works but not a black then I'd think it's maybe the key(s) themselves or that the ECU has lost track of them.

If you search the Interwebz you can find the procedure a locksmith would do to program a key if you still have a black one. That's the one involving all the steps, insert key, remove key, open door, close door, step on accelerator and brake simultaneous, etc. Maybe you can get the ECU to relearn.

But if only a grey key works and no black keys do still then you may be in a security mode.

The electrical difference in the two keys is that a black key is a master and can make more masters or sub keys but a grey is a sub key and copies can't be made from it. That's why Toyota recommends giving only grey keys to shops or valets, so a new key can't be made to defeat the immobilizer.

If no black keys work or can be found you need Tech Stream to make a new master key, the rub your belly, pat your head in the driver's seat procedure can't be used.

I worry about this sometimes when I unthinkingly give a black key to a shop. You can make the immobilizer forget all the keys except the one you're using and make it relearn to only recognize the one(s) you have. But this functionality I bet means there's a way to glitch the firmware and give you nuisances like this sometimes.

The battery did die a few times during the winter oddly enough, which I never could figure out. I suppose I could try and re-link the black key, see where that goes. I haven't looked for the security light while cranking but will check next time.

 

[DanInDenver]

The fuse box EFI immobilizer issue was for me very intermittent.
Does the valet key work when the main key won’t. As in right after each other switching back and forth?
I wired up the bypass 2 years ago and have been trouble free since.

 

[AdamKFarmer]

The fuse box EFI immobilizer issue was for me very intermittent.
Does the valet key work when the main key won’t. As in right after each other switching back and forth?
I wired up the bypass 5 years ago and have been trouble free since.

Correct, immediately after. What bypass?

 

[DanInDenver]

Post #4 the second Mud post.
If the valet key works consistently then it’s probably not that fix.
You could try a new key off Amazon and then program that as a master. I think Ace cut the key for me.

 

[AlpineAccess]

Just a note on the Amazon fobs, I went through a few and am now back to Toyota receiver in a YotaMD frame. The toyota one has 3x the range, is much more consistent, and low and behold is actually waterproof (what killed the others I believe). I wasn't negligent, but keep a car key on me when running and sweat was enough to kill the Amazon ones.

 

[AdamKFarmer]

Just a note on the Amazon fobs, I went through a few and am now back to Toyota receiver in a YotaMD frame. The toyota one has 3x the range, is much more consistent, and low and behold is actually waterproof (what killed the others I believe). I wasn't negligent, but keep a car key on me when running and sweat was enough to kill the Amazon ones

Jack-
Did you buy a new receiver from Toyota? I see they are quite pricey.

 

[AlpineAccess]

Jack-
Did you buy a new receiver from Toyota? I see they are quite pricey.

I did, it was a tough decision just because the knock off's DO work and are so cheap. I waited for a sale and landed one for about $110 from McGeorge Toyota.

That being said, the quality is dramatically better IMO, and it was one of those things that I figured was used multiple times a day so was worth it. It unlocks more consistently, has truly been waterproof, and I can lock the car from a distance (around 30 feet) whereas sometimes my knockoffs I was having to walk back to within about 5-10 feet of the car and have direct line of sight. Even with fresh batteries.

The range really matters to me, as does being able to lock the car from inside my house, for example.

 

[2wheelbob]

Been through the intermittent no-start issue on my wife’s 2000 model year hundy a few times. Each time, replacing the main fuse block fixed the issue. We tried the different key fix to no avail. The fuses all checked out fine as well. It seems at some point, the voltage out of the fuse block was reduced to the bare minimum needed for the ecu to ‘unlock’ the security feature. If the voltage dipped below the required minimum, (I can’t recall the exact value) the truck wouldn’t start. If it rose to the threshold, it would start. I found a thread on mud about a jumper setup as a field fix to get you home. I printed it out and keep a copy in the glove box as a ‘just in case’ thing.

 

[DaveInDenver]

I'm still struggling to understand why the immobilzer getting marginal voltage would still work with the grey key but not the black key. AFAIK there's no difference in them electronically. It's what the immobilizer does when an particular transponder comes into range of it, so it's what's contained in the stored cryptographic key.

Perhaps someone can clarify a couple of things. When your immobilizer doesn't work with a black key but does with a grey key what is the security light doing?

It's supposed to flash constantly about once per second whenever it does NOT see a key, it'll go off completely in the presence of a master and it will illuminate for 2 seconds and then go off when it see a sub key.

When they are made originally it's really just the order they're made. The first two the ECU is given are masters and the third is a sub as I understand the protocol. Keys made is where I get more fuzzy. I think they may be subs regardless of their color since I think the ECU may only recognize 2 master keys. In newer vehicles I think there may be a hard limit of keys but I think older junk like a 100 series or my Tacoma can hold more.

If replacing the fuse fixes it then I'm curious why. I'm still supposing it's that the transponder in the key itself is compromised, be that due to water, exposure to something like a strong EM field, etc. A weakening immobilizer might be masking another problem, although it takes two to tango so it is itself something that was in need of repair eventually.