Immobilizer/EFI relay bypass issue (3 Viewers)

[Caimbeul]

So when I first got my truck it left me stranded and I racked up a $300 tow bill. I went through everything trying to figure out what caused it to not start but after the truck was towed back to my house it started up fine. 2 weeks starting great and then randomly leaves me stranded again. That’s when I found medtro’s immobilizer fix. So I quickly built my own modeled off of his that day in an attempt to avoid more towing costs but the truck started again. Well… fast forward to this past weekend and it left me stranded again so I took the relay bypass I had made and tried to line up the wiring to match his photos. The truck immediately started up and ran great BUT it drained my battery completely over night so I clearly did something wrong. Here’s a photo of the harness I fashioned. Any guidance is appreciated.

 

[Goslow]

You have two wires spiced together into the single relay contact. One goes to your fuse, but I’m not sure where the other one will go to. Doesn’t look right. Here’s how mine is constructed. Many thanks to Medtro for creating this fix. I’ve had two no start occurrences With this set up, but it starts when I slightly wiggle the spade lug that goes into the 20 amp fuse. New fuse box on order.
This is my observation.

 

[BullElk]

I don't remember the configuration by heart but it is well explained in Medtro My immobilized fix thread.

However, the way you did it that drained your battery is good to use just to get it cranked and driven until the proper fix. But take it out when not driving. It is better than a tow bill

 

[medtro]

So when I first got my truck it left me stranded and I racked up a $300 tow bill. I went through everything trying to figure out what caused it to not start but after the truck was towed back to my house it started up fine. 2 weeks starting great and then randomly leaves me stranded again. That’s when I found medtro’s immobilizer fix. So I quickly built my own modeled off of his that day in an attempt to avoid more towing costs but the truck started again. Well… fast forward to this past weekend and it left me stranded again so I took the relay bypass I had made and tried to line up the wiring to match his photos. The truck immediately started up and ran great BUT it drained my battery completely over night so I clearly did something wrong. Here’s a photo of the harness I fashioned. Any guidance is appreciated.
View attachment 3950579View attachment 3950580

As mention in PM, please show how it is connected to the vehicle. It is either wrong connection or bad relay.

 

[medtro]

I’ve had two no start occurrences With this set up, but it starts when I slightly wiggle the spade lug that goes into the 20 amp fuse. New fuse box on order.

I would connect the fuse holder to the battery "+" post with a ring terminal and return the new fuse box.

 

[BamaHoo]

The post linked below may help sort yours out, I agree with the comment regarding the two wires you have running from one relay terminal. Not sure what the unfused wire is meant to do in your setup, although I suppose it could be connected to the EFI fuse holder on the "truck" side (non-technical term--the side that's not the power/battery side of the fuse) to feed the ECM with always-on power per the wiring diagram in my post below.

If you are tapping the fuse holder for the power to your relay, you might instead wire the power directly to the battery (with inline fuse, of course). I feel like it's better to ensure the power supply to the relay isn't affected by the wonky fuse box, but maybe that's just me.

Need help with P1600 Code

I need some guidance on troubleshooting a P1600 code on my 2000 LC. Saturday morning I replaced the PCV valve, grommet, ventilation hoses, vacuum hoses, and most of the vapor hoses at the charcoal canister. Was feeling good about it, especially since I was able to retrieve the PCV grommet in...

forum.ih8mud.com

Medtro's original post is where to start.

 

[Caimbeul]

As mention in PM, please show how it is connected to the vehicle. It is either wrong connection or bad relay.

I'll snap a picture today and post it but...
Relay pin 87 goes to fuse box E slot and branches off to either one side of the fuse port for power (A or B) OR extended to be directly connected to the positive battery terminal.
Relay pin 85 goes to fuse box C slot
30 to F
86 to D

I connected it this way yesterday and it started once, died, and now just cranks. Perhaps this isn't actually the starting issue I'm having but if it isn't I'm at a loss. The truck has 74k miles. Brand new battery, starter, knock sensor, cam seals, fluids, performance plugs, Walbro fuel pump, performance injectors, and more... The only other thing I can come up with is the GReddy E-Manage that it is tuned with is failing somehow. It had a Viper alarm with remote start and it's own immobilizer that I thought was the problem so I had a shop completely remove that.

 

[Caimbeul]

You have two wires spiced together into the single relay contact. One goes to your fuse, but I’m not sure where the other one will go to. Doesn’t look right. Here’s how mine is constructed. Many thanks to Medtro for creating this fix. I’ve had two no start occurrences With this set up, but it starts when I slightly wiggle the spade lug that goes into the 20 amp fuse. New fuse box on order.
This is my observation.

View attachment 3951067

Your 87 wire is only going to the fuse pin for power?

 

[blatant]

Plus a few stars for @medtro Fixed me up 8yrs ago or so. 100 Never missed a beat after that. He is a good, well versed dude.

an oldie but a possible goodie thread.

100 series cranks but won't turn over / start

I just had this problem tonight, 1st time, ever. 2001 lc. 205k. Wouldn't start but cranked strong as could be. Tried it a couple time and it started fine and good to go. Really stunk though. Meant awful situation being stuck! So I've searched and read all the threads I could find. In...

forum.ih8mud.com

 

[medtro]

I connected it this way yesterday and it started once, died, and now just cranks.

Do you have flashing security light while cranking?

If it drained your battery with this connection, then you have a sticky relay.

 

[Goslow]

Your 87 wire is only going to the fuse pin for power?

Correct. Others in this thread have suggested that this wire be run to the battery positive terminal for a more secure fix. I ordered a new fuse box from Partsouq because I want to repair this permanently. If there is such a thing. Partsouq is half the cost of Dealer price.
I picked up a complete fuse box from a 99 Land Cruiser at my local salvage yard for practically nothing so that I could see how it is constructed and so that I could get a complete set of spare relays. After I install my new fuse box, I plan to tear down my failing fuse box to see if I can do a failure analysis. There is a fundamental failure mode in these fuse boxes and I’d like to see what it is, if I can. I don’t have access to a ring magnifier or microscope currently but I’ll see what I can do and if I can find an assignable cause, I will report it back to the forum.

 

[Caimbeul]

Do you have flashing security light while cranking?

If it drained your battery with this connection, then you have a sticky relay.

No security light I can see. I went and got a new relay today to test that out. I also put a 30a fuse in the fuse slot and connected the 87 wire split directly to the positive battery terminal. Still… just cranking. The time the battery drained completely I may have had the wires mixed up a bit but I’m unsure.

I have no clue what is causing this starting issue.