UZJ100 immobiliser fault

[Jon Wildsmith]

We suddenly had an immobiliser issue this week and no amount of fiddling with the fuse, jumping it, hitting it etc would make it work even briefly. There's a lot about this on ih8mud but I can't find any threads with an immobiliser fault where the fuse box isn't implicated so I figured I'd take it apart and see if there was anything to fix in there. It didn't fix our problem but here's what I found in case it helps someone else to know what's in their fuse box


Fusebox with the suspect fuse and relay circled in red

I removed the fusebox from the truck. If you undo the clips holding wires to the casing you can tip the fusebox up enough to get at the connectors underneath and disconnect them. With the fusebox on the bench I removed the bottom cover but I forgot to take a photo of that. That cover is held on by clips around the sides and 2 plastic rivets towards the middle that I had to drill the tops off to release it. Under that cover this is what you've got.

The tracks are laid out on another layer of plastic and lift off. Some of them have male spade connectors that go through to layers underneath and some form the connections for the plugs on the wiring loom. I put the parts in a pile (on the cover I forgot to photo) to get the next layer of plastic off thinking I'd be seeing the back of the fuses!

Turns out there are a few layers, I didn't count but 5 I think:

With all the layers removed the back of the fuse and relay connectors are revealed. They are like double ended connectors pushed into the holes, fuses or relays push into the top side and these tracks push into the underside. The 2 connectors for the EFI fuse circled in red were very loose and barely making contact but no sign of carbon or corrosion.

I didn't feel the connectors were repairable and doubt I'd be able to get replacements so I removed them, drilled out the holes, put the tails of an inline fuse holder through the holes and soldered to the tracks that would go into those holes:

Then I put the rest of it back together. The connectors under the fuse box all only fit in one place.

 

[frank rabbets]

Did it work?

 

[Jon Wildsmith]

No it didn't work, I said that in the intro text

 

[frank rabbets]

I wonder if you have solved the fault but the system needs resetting? My 80 will not start sometimes after I have disconnected the batteries. If it does not work I have to disconnect the batteries again then connect them with the ign on.

 

[Jon Wildsmith]

It was worth a try but that didn't work.

 

[frank rabbets]

I still reckon that joint was the start of your problem.

 

[CANEX]

Do you have the flashing red light on your dash Jon? I'm not sure what year they changed (or if they did) but mine has a sensor built into the ignition key & when the key is inserted the red flashing 'security' light stops flashing - showing the immobiliser is off.
If you have that it shows if the sensor ring & key fob are talking to each other.

cheers
Chris

 

[Jon Wildsmith]

The fault is that the little red security light doesn't stop flashing when valid keys are inserted and the engine remains immobilised. I've changed the transponder coil and amplifier so it's not those and is looking like being the ECU so I'll look for an ECU now.

 

[CANEX]

Just wondering because I changed my ignition barrel & forgot to put the transponder ring back in & it wouldn't start!

 

[Xetabur]

I've had this same issue 3 times (the 3rd time being today). I eventually get it started but it's getting old fast. My LC is a 2000.

Edit-it looks like if I don't turn the key all the way it will start fine. Any further than half way I just get a click somewhere in the engine compartment.

 

[frank rabbets]

I saw my brother yesterday who specialises in Renaults. The 2000 year cars were plagued with immobiliser/ECU faults. It was a transponder system and the ECU used to fail. There was a process whereby the immobiliser part of the ECU was bypassed to get the car to start but you then did not have a functioning immobiliser.

Were transponders unreliable? Don't seem to see them anymore.

 

[Jon Wildsmith]

I'm awaiting delivery of some low ESR capacitors to change the ones in the ECU, they can go faulty without visible signs so it's worth a shot. If that doesn't work it's booked into an ECU repair place for testing and they may be able to bypass the immobiliser. Also looking for a second hand ECU with keys but no luck so far, seems they are in demand so may be a common fault.

 

[frank rabbets]

Is it worth giving Toyota a ring. Some of their prices are all over the place. I just bought 4 discs together with pad sets for £290 for the 80. They were in dusty Toyota boxes. Perhaps they are getting rid of old stuff or trying to raise some short term money. Japanese economy is a bit desperate for quick money.