Ben’s 2004 HZJ105 STD Spec 1HZ Manual

[Ben Stratford]

Several electrical issues remain since purchase in Summer 2024:
1. Horn not working ( It did a month ago )
2. Oil Pressure Gauge not working
3. Tachometer not working

In trying to trace the faults, connections seem to be via the drivers footwell kick panel junction box:

As you can see there have been connection issues here before as someone has added wiring with a 5A fuse flapping in the breeze.
To add to the enjoyment the stack of manuals I have show totally different diagrams for all 3 fuse boxes.
Looking at the Horn circuit first: the place where the horn relay is supposed to be in the main engine bay fuse box is empty.
There is no continuity between the horn fuse and the horns so there must be a relay somewhere. Does anyone have any ideas as to its location please?
As I said it’s not in either kick panel or the main fuse box or anywhere else in the engine bay.
Does anyone have a picture of the circuit in an Australian vehicle ( where it was imported from ). My manuals may be for European vehicles.
Does the horn have to be activated by the original switch or could a separate circuit be added with a momentary switch installed somewhere handy for the MOT man to look at in two weeks time?
This is the diagram I have

 

[Ben Stratford]

Ok so been working on the horn issue. Thought it may be the clock spring. Changed that but it wasn’t faulty as it turns out. One pin had lost continuity but it was an unused pin! Anyway, the horns both work when connected to the battery. The fuse is ok. There is no relay in this circuit unless it’s one of those invisible ones under the fuse box or something.
Auto electrician now engaged to help.

 

[GeekOKent]

Just keep in mind the OE horn sounds about as loud as a dog farting. While you are at it, maybe worth putting something with a bit more decibels

 

[Grimbo]

I reckon there is a relay somewhere.....
The horn button supplies an earth path for the coil on the horn relay..... and power comes from the horn fuse straight to the horn... on the factory diagram but you're well capable of sussing that so I wonder if a multi plug somewhere has had corrosion issues and matey hasn't wired up an alternative..... if you supply an earth to the correct pin at the clock spring plug does the horn then work ?
Seeing as the horn seems to be a VE - issue could that also be the cause of your tacho and oil pressure gauge not working ? do they share a common VE- source ?

 

[Ben Stratford]

Thanks @Grimbo for the suggestions and insight.
I tried grounding the circuit at the relevant clock spring connection but no joy.
After hours of searching there may be an answer as to where the relay is for the horn.

A clip on the net shows such an integral relay. The pic shows part of the fuse box cut away to reveal a built in relay:

Why???
I won’t get a new fuse box by mot time if available at all so we may have to integrate a stand alone relay and tap into the circuit wiring.
Yes @GeekOKent I was not impressed with the horns when they did work so shall indeed seek something louder
If the sparky succeeds I will then book him again for the tachometer and oil pressure issue.
The previous owner said it may be a comparability issue due to the engine having been replaced with a new 1HZ with different sensors or something but he never got to the bottom of it.
Again if necessary stand alone guages may be the way forward If we can’t get the original ones going.

 

[Jon Wildsmith]

I think you can disassemble the fuse box and either replace the relay directly on the board, or more likely remove it and remote mount it outside the box with fly leads? I took one apart of my old petrol 100 to fix a common ECU fuse problem and documented it on here somewhere.

Found it: https://www.landcruiserclub.net/community/threads/uzj100-immobiliser-fault.143935

 

[Ben Stratford]

I think you can disassemble the fuse box and either replace the relay directly on the board, or more likely remove it and remote mount it outside the box with fly leads? I took one apart of my old petrol 100 to fix a common ECU fuse problem and documented it on here somewhere.

Found it: https://www.landcruiserclub.net/community/threads/uzj100-immobiliser-fault.143935

Your old post is gold dust @Jon Wildsmith thanks very much. I’m confident now that whithin 24 hours the horn will work one way or another

 

[Ben Stratford]

Ok, horn now working via standalone switch. Decided I will order a new fuse box with the integral relay so it will be simple to revert back to standard this way.
Next to investigate the oil pressure gauge!

 

[nick_the_fish]

Glad you got the horn working.

re. Oil pressure gauge - mine went too. It was the sender unit, Roughtrax sell Toyota ones (or at least they did), changed it and it's working fine again. Hopefully that one will be easier.

 

[Ben Stratford]

Glad you got the horn working.

re. Oil pressure gauge - mine went too. It was the sender unit, Roughtrax sell Toyota ones (or at least they did), changed it and it's working fine again. Hopefully that one will be easier.

Thanks @nick_the_fish
Started looking into it and the funny thing is that I can’t find a sender unit. I think the previous owner may have removed it to use the hole for the oil return from the turbo.
Have ordered a 1HZ engine manual to assist with the issue. Once i know where it should be - usually under the oil filter I think then I can confirm what’s happening. If necessary I can get a tee to allow a sender to be added. Hopefully the wire hasn’t been removed

 

[nick_the_fish]

From recollection it is indeed just under the oil filter, but my truck is having a Dynatol treatment done so I can't check until it comes back, but I can take some photos once it is back if you need them.

 

[Ben Stratford]

From recollection it is indeed just under the oil filter, but my truck is having a Dynatol treatment done so I can't check until it comes back, but I can take some photos once it is back if you need them.

That’s very kind thanks @nick_the_fish.
I have just received my 1HZ Engine Manual for the HZJ105 / 100 and it confirms south east from the oil filter but a photo would be very helpful too please.
I believe this is now where my oil feed is for the Turbo and there is a sender for an oil pressure warning light teed off from the same hole. Presumably to shout if the turbo oil feed stops.
So I will look to see if the original sender wiring can be found then order another tee and sender to hopefully get things reinstalled properly.
I’m thinking that I should remove the current sender and install the proper one to see if the gauge works. If so then tee off the first tee to mount both senders and turbo oil return pipe

 

[Ben Stratford]

All I wanted to do was change a bulb for the heater control…..

Had to remove the two central heater vents, the whole centre dash including stereo then separate this ensemble into two halves then remove the back cover and wiring etc.
discovered that the ash tray had a lamp which is also U/S but it’s all good fun.
Will hopefully be able to use these bulbs and transfer the green rubber lamp covers over…

 

[felix2566]

One of the few areas I think Toyota did a less than average design job is the dash assembly. It's such a pain to take apart.

 

[Ben Stratford]

All I wanted to do was change a bulb for the heater control…..View attachment 340217

Had to remove the two central heater vents, the whole centre dash including stereo then separate this ensemble into two halves then remove the back cover and wiring etc.
discovered that the ash tray had a lamp which is also U/S but it’s all good fun.
Will hopefully be able to use these bulbs and transfer the green rubber lamp covers over…
View attachment 340218

Ok so the black lamp holders are not compatible with the blue ones. So removed the lamp from the black one and installed it in the blue one with the green “condom”. Worked a treat. It turns out 3 of the 6 lamps had failed. Now to rebuild from this…

 

[felix2566]

I was wondering when I saw the different colours if they there the same base parts

 

[shane11r]

That’s very kind thanks @nick_the_fish.
I have just received my 1HZ Engine Manual for the HZJ105 / 100 and it confirms south east from the oil filter but a photo would be very helpful too please.
I believe this is now where my oil feed is for the Turbo and there is a sender for an oil pressure warning light teed off from the same hole. Presumably to shout if the turbo oil feed stops.
So I will look to see if the original sender wiring can be found then order another tee and sender to hopefully get things reinstalled properly.
I’m thinking that I should remove the current sender and install the proper one to see if the gauge works. If so then tee off the first tee to mount both senders and turbo oil return pipe

Ben, this may or may not be relevant, late 2002 an environmental mod was made to these vehicles (In Australia) , throwing a lot of the wiring out of whack compared to pre 02 wiring diagrams. There was a exhaust gas recirculation (EGR) installed along with some supporting sensors and a control unit. I believe its called the emission control unit (ECU) not engine control unit. Since this was the only bit of "smarts" the vehicle has and the dash didn't natively have a check engine light the glow plug light was repurposed as the check engine light" Youe glow plug light will act as normal when you first turn on the ignition but also can turn on when the car is running to signal an issue with the ECU.
more importantly many signals were parsed through this ecu. However The vehicle with run without it. (possibly with a glow plug light on) I can tell you with certain if you unplug one of the harnesses of the ECU you will loose your taco and oil pressure gauges however all other gauges will work. The unit is a silver box behind the glovebox.

 

[Ben Stratford]

Ben, this may or may not be relevant, late 2002 an environmental mod was made to these vehicles (In Australia) , throwing a lot of the wiring out of whack compared to pre 02 wiring diagrams. There was a exhaust gas recirculation (EGR) installed along with some supporting sensors and a control unit. I believe its called the emission control unit (ECU) not engine control unit. Since this was the only bit of "smarts" the vehicle has and the dash didn't natively have a check engine light the glow plug light was repurposed as the check engine light" Youe glow plug light will act as normal when you first turn on the ignition but also can turn on when the car is running to signal an issue with the ECU.
more importantly many signals were parsed through this ecu. However The vehicle with run without it. (possibly with a glow plug light on) I can tell you with certain if you unplug one of the harnesses of the ECU you will loose your taco and oil pressure gauges however all other gauges will work. The unit is a silver box behind the glovebox.

Fantastic @shane11r will see if indeed this mod is installed and implicated. Thanks very much for explaining it and sharing.

 

[shane11r]

I amalgamated the most accurate fuse data i could find into one image file
you can see here location of the ECU

 

[Ben Stratford]

That’s great thanks very much