My immobilizer fix (2 Viewers)

[medtro]

I got the famous crank but not start immobilizer problem. I replaced the 20A EFI fuse with a 30A fuse and it started right away. However, it was a temporary fix. I had the same problem again 4 days later. This is what I did to get the engine started. It has been working with no problem for close to 4 weeks now, I thought I would share this with the group.

Fuse terminals: A, B
EFI relay terminals: C, D, E, F

With the EFI fuse in place and relay removed, I ran a wire from the battery positive terminal to terminal F, engine started with no problem. This tells me problem was at upstream or bad relay.

PS: This is a good wire to have in the car for emergency fix.

Factory EFI relay tested good. Next, I shorted terminals E and F, engine cranked but not started. This tells me the power from terminal E was not good enough to start the engine. With the help of voltmeter, I found out there was 0.44V voltage drop between the battery and terminal E with factory 20A fuse in place. Voltage drop was 0.14V with 30A fuse. The engine wouldn't start even with 0.14V voltage drop. I came up with the following to bypass the internal circuit between terminals B & E in order to reduce the voltage drop between the battery and terminal F.

I used a Tyco V23234-A1001-X043 Mini Relay 12V. Make sure the relay you use has suppression protection if you are going to do this, otherwise this could cause damage to your ECM.

Wiring diagram:
Terminal A to 20A inline fuse to terminal 87 of Bosch relay
Terminal F to terminal 30 of Bosch relay
Terminal C to terminal 85 of Bosch relay
Terminal D to terminal 86 of Bosch relay
No connection for terminals B and E

Factory EFI relay can be used in this setup. I used Bosch relay because I want the relay to sit flat in the fuse box. I also put a piece of high density foam between the fuse box cover and Bosch relay to "secure" it better in place.

 

[Saddletramp]

Well done Jackson

 

[sean2202]

Great job! Interesting that the engine would not start even on a 0.14 voltage drop. How could the original problem be fixed without the new system?

 

[medtro]

Great job! Interesting that the engine would not start even on a 0.14 voltage drop. How could the original problem be fixed without the new system?

A new fuse box will fix the problem.

 

[wildsmith]

The internal connection on terminal B is bad, looks like a production fault. Having seen inside the fuse box and what the problem is, a bypass like this should be reliable and a new fuse box will just look neater but not work any better.

 

[elk]

This is another example of the amazing knowledge base here on Mud. I hope to never have to use it, but I now have this thread filed away among the other useful minutea.

 

[Bomar]

@medtro clean setup. I bet you could make a little money making these. Very clean work. It is something I would keep as a spare incase it happens.

 

[Ninja Cruiser100]

@medtro clean setup. I bet you could make a little money making these. Very clean work. It is something I would keep as a spare incase it happens.

I agree - Depending on cost I would buy one.

 

[medtro]

The internal connection on terminal B is bad, looks like a production fault. Having seen inside the fuse box and what the problem is, a bypass like this should be reliable and a new fuse box will just look neater but not work any better.

I agree that terminal B is bad. I was able to reduce the voltage drop by poking terminal B with sharp object.

 

[medtro]

Great job! Interesting that the engine would not start even on a 0.14 voltage drop. How could the original problem be fixed without the new system?

It may start with 0.14 voltage drop if the battery is healthier. I believe the immobilizer has a minimum voltage threshold.

 

[medtro]

@medtro clean setup. I bet you could make a little money making these. Very clean work. It is something I would keep as a spare incase it happens.

I agree - Depending on cost I would buy one.

I would be happy to help. Please PM me if you would like to have one.

 

[drjman]

I would be happy to help. Please PM me if you would like to have one.

Is there another similar relay that could be purchased at a local auto parts store? I currently have a non-starting cruiser after experiencing the issue for a while. None of the tricks work now.

 

[medtro]

Is there another similar relay that could be purchased at a local auto parts store? I currently have a non-starting cruiser after experiencing the issue for a while. None of the tricks work now.

Remove EFI relay, run a wire from the battery positive terminal to terminal F as shown in the 2nd picture above, then try to start the engine. If the engine doesn't start then this bypass trick will not help you, your problem is somewhere else. I was not able to find a similar relay from local parts store. You could use your factory relay as well if it is still good. A few people has asked me to make this, I have an extra set for sale now. Please PM me if you are interested.

 

[drjman]

Remove EFI relay, run a wire from the battery positive terminal to terminal F as shown in the 2nd picture above, then try to start the engine. If the engine doesn't start then this bypass trick will not help you, your problem is somewhere else. I was not able to find a similar relay from local parts store. You could use your factory relay as well if it is still good. A few people has asked me to make this, I have an extra set for sale now. Please PM me if you are interested.

I don't see any voltage drop between the 20a and relay. Now I'm wondering if my relay is bad. I don't have a way of jumping from the battery to F yet, but i'll try that next.

For a few weeks now my wife has been reseting the 20a fuse and that would get the immobilizer light off and the engine to start. Yesterday, however, that trick no longer worked.

Is there a special electronics tool needed to test the relay itself?

 

[reznunt]

Subscribed and bookmarked for future use, but hopefully not! Thanks!

 

[medtro]

 

[Ninja Cruiser100]

Great vid, thanks.

 

[drjman]

Ok, so I jumped from battery to F and it started. I tested the relay and it engages and has continuity. Voltage at A is good, but D is about 11.5v with ignition to ON. I assume that is not enough to fire the relay and why the EFI isn't getting the needed power. I have some wiring diagrams through AllDataDIY, but it looks like a lot of relays share that same power source as D. I'm going to keep trying to find the real source. In the meantime, if anyone has any ideas, I appreciate the input.

It seems my issue is slightly different from most immobilizer issues. Probably still a bad fuse block.

 

[ponytl]

Pretty sure I posted the exact fix 2 years ago even made about 8 of them and sent em out for free to those who asked ( all the parts i had) the relay is a $2 part off ebay but it is common to your aux. light light relay most of you use... also the same relay for the tilt trim for my outboard (which is why i had one with me) I build my first one in a parking garage where my wifes lx470 was stuck built with parts and wire in the bottom of my tool bag... yours is much cleaner than my first one...

 

[medtro]

Ok, so I jumped from battery to F and it started. I tested the relay and it engages and has continuity. Voltage at A is good, but D is about 11.5v with ignition to ON. I assume that is not enough to fire the relay and why the EFI isn't getting the needed power. I have some wiring diagrams through AllDataDIY, but it looks like a lot of relays share that same power source as D. I'm going to keep trying to find the real source. In the meantime, if anyone has any ideas, I appreciate the input.

It seems my issue is slightly different from most immobilizer issues. Probably still a bad fuse block.

What is the voltage:

• Between +ve and -ve of the battery terminals?
• Between E and -ve battery terminal?

Short terminals E and F and see if you can have the engine started. My wild guess is engine won't start and your problem is between B and E since your relay tested good.