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Iwan's lc5

Had abit of a go at this after work... JB1 in particular..

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So how this checks out on this truck.. the wires come out of the pins 7 and 1A 17 not the 8's /18 my mistake when marking up.
Continuity wise on just this line with the red wires... 1A pins 7 and 17 and 1B pin 7 hold continuity between the 3.
Theres a matching wire for t9 1 in 1A pin 17 but as this is connected to 1B 7 and 1A 7 then this bring in two wires into play here... we know that t9 1 is a feed wire to power the system which is red with two silver dashes then a 20mm gap then two silver dashes and so on..

1A pin 7 red black stripe with two silver arrows pointing to the connector then 20mm gap then repeats along the wire... seems to suggest power goin in.

1B pin 7 red black stripe double silver dashes..... I'm wondering if this is the power feed for the security light? Because it's on when the immo is activated..

1C, 1D, 1E all red blue and pin 7 are essentially one wire connected in jb1, so 2 power circuits in this block..

Something to think about.. what is known is that when you turn the ignition off and pull the key out then the immobiliser is activated...t9 1 has constant ignition off power applied to it from the under bonnet constant power fuse box.... Ignition is turned off which stops the ignition on power to t9 pin 2... so feeding t9 pin 1 power full time I dont think will work.... because it has to be known that the key isn't in the ignition. There has to be some kind of switch for the want of a better word which turns on the t9 pin 1 circuit and activates the immobiliser..

Just something I was thinking about today.. Some connection to the ignition barrel in there...:think:
Just doing a bit more investigation. Haynes diagram shows The ECU-B No 2 fuse, and that wire going to the DRIVERS SIDE FUSE BOX (not JB1)..... connector B4.

Then out of the fuse box on L4.

So that 'IB/IL' in some diagrams is actually the drivers side fuse box!

See attached for the fuse box diagram

You should be able to get to B4 without taking the fuse box out. I think L4 (even though its not on that diagram) is on the back side of the unit from what I remember....

Haynes then has it going from fuse box L4 to what its calling 'No 2 junction connector'. I dont know if this is possibly JB2? It enters on B3 and leaves on D4. It might be worth checking the wires on junction box 2 (in the middle of the dashboard I think)?

I've attached JB2 details - maybe those wires will match? I think we're matching together about 20 wiring diagrams from 20 sources, so they might be called different things?

Indeed regarding the diagrams I'd say that different models, manual or auto, age as in the research and development.. but do give a good idea of an area to look in...

But considering there's 33 ecu's on this.... it's a mine field under the dashboard! LOL
Haynes Doc attached... interesting bits circled in red I think

What these show is that wire from ECU -B providing 12 volts also goes to other stuff - door locks, power windows and alarm siren! So that might provide more clues.

Posts crossed - will read your updates now :)


  • Xerox Scan_04092023213646.PDF
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There has to be some kind of switch for the want of a better word which turns on the t9 pin 1 circuit and activates the immobiliser..
There is a key switch in the barrel I think which you tested as part of your initial techstream tests?
Thanks for the Haynes chart... I couldn't at the time locate the back of the barrel as the surround was fitted at the time..

So regarding the key switch.. if you enter the truck and just locate the key but only 1/2" it passes the initial point right at the beginning.. so is it at that point does the security light go out. Or does the key have to be fully inserted.. for the security light to go out?
Ill check that in a minute....

But the keyswitch should report on/off on live data so you can see if its working
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The key doesn't go in all the way, i.e. up to the fob, but allowing for that, mine is the same as Karl's, - about 40 %, just to confirm/double check.
Thanks Guys, handy to know this as testing can fit the key to 40% and a change of continuity will reveal the correct wire..

On the haynes it's good to see ecub no.2 there, so there's a real quest to find ecu b to confirm the begining of the wire feed and of course will reveal the wire to the internal fuse and relay box... also did track down the burning smell from there... @frank rabbets the little dogs nose was pointing to this area so a very good indication!!!

Also to check JB2 as havent been in there yet and possibly t9 1 can be found..

Got some good leads here so roll on after work!!
At the end of the day though, all you need is a working 12 V to T9 pin 1?

I've found out that my test and trace on this location is similar to the covid app! But not expensive at all!

I had got the pin one confused with pin 8 which much earlier on had tested and identified!

I feel like a right prat... because the red wire suggested that it was a power wire and it powers the amplified key reader! Which is here and by the laptop and does indeed smell burnt! :think::laughing-rolling:

But this location with the white red has continuity with many of the the corresponding white red stripe wires in the area..

Because of this mistake and full on work load am going to return to this on Saturday, but as now I have more knowledge of where the wires are and areas to check.

I aim to re go over the wire testing for the wiring for the immobiliser ecu just to confirm what I've done..

Just feel a bit over whelmed by it at the moment, but if the wires check out good.. then it's progress! :thumbup:
Had a successful hit on this yesterday morning.. it's better to restart this work after taking a break from it!


Very scruffy writing but it may help some one who needs to check this t9 wiring circuit.

Have traced and tested continuity on all wires to the immobiliser ecy t9. Thats finding both ends of the wires.. can safely say that this wiring is good.

Have the door switch to check t9 pin 4 but remembered that there is a test with the battery connected so am going to start fitting the loom back in place and connecting up etc as quite a lot is sat disassembled... so aim to follow the 1482 pdf testing with the battery connected. Plus connecting up to techstream.

The problem is getting whittled down to either of these:- immobiliser ecu t9, the key amplifier, the engine ecu which controls t9, door switch needs checking and to just confirm t9 pin 1 has the connection to ecu b fuse..

Pretty good going when you know where the wires are!
A little update on reconnecting the batteries...

Connected up and walking round to the drivers door, security light flashing,, key in light goes out.. too much to expect the engine to start.

Connected to tech stream all ecu's/modules in yellow i.e. main ecu aware of the rest.

Health check's performed and at first noticed that certain items are disconnected and giving codes for immo, cruise control and disconnected airbags.

Then the further checks performed show that there's less and even lesser recognition of the rest of the modules... which results in the ecu only recognising engine, ECD (trans).. then there's as before taking it apart a failure to even connect to the main ecu..

So as reconnecting the batteries after time with the ecu disconnected too on re connection it works ish just for a short while when connecting to tech stream then it it dies to a point where it isn't even noticed by the lap top.. luckily had a saved caption from the first tech stream connection which shows the same thing as in the end result of this ecu has died after a short time 1/2 hr of laptop connection...

When testing the system have been real carefull not to pull the wires on the connectors and the paper clip connection to the wiring plugs haven't been rough on them. Even though at one point was tempted to teach it a lesson by cutting all the wires from the connectors real close to the plugs and smashing up the plastic control modules with a 5lb club hammer! Only kiddin but I really think the ecu is f'd and if proven true will take the 5lb to the f'ker! :thumbup: :laughing-rolling:
Just located a crash damaged 2005 lc5 with the correct ecu numbers..

So thinking what to buy off it..

ECU, immobiliser t9 ecu, the key amplifier and a key to obtain the chip out of and the cruiser control stalk. £350 inc vat and postage..

@karl2000 do you think I need any other modules?
Buy the whole vehicle - you know what these 120's are like, lol.

Who is it from, just out of interest, I've had good and a real bad bastard who sends junk.
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I could create a youtube channel and call it "Will this 120 start this time!" Endless content.... LOL

Its in a breakers yard on ebay, will have to get in contact as haven't heard back, He was looking for the key!
That would make interesting viewing - don't bleep out the swearing !

It was eBay breakers I was talking about with experiences.

Give him time Iwan, there's only a million keys to sort through, lol.
Well well well am struggling to get hold of the kit I need to get this sorted.. been messed around by the ebay 120 breakers.

Am considering to go back and buy the lc4 2006 to convert this from a lc5 and change the heater and loom etc... at expense..

Am going to go back to my 1992 lj71 auto body swap to a 1988 lj70 with a 1kzt project as the spanner work is workable LOL!

Should of. could of, would of bought the lc5 ecu full set at the beginning of the thread.... but no point in crying but an electrical fault is a lot harder to sort than doing a body swap on a lj70!

Will be keeping an eye out for the relevant parts to fix this..... and will get this sorted!! :thumbup: