Thread: HDC

I've come across a post on another forum which had a really easy way to test if hi/lo switch is working correctly. It only works for Auto's however.

Shift to Low range, then push the "Mode" button on the Auto shifter housing. If the Hi/Lo detect switch is working correctly the "M" will light on the dash. If you get "S" the switch or wiring is faulty.

cheers
Paul

Thanks Paul.
The dash light for manual mode comes on in low range when I select low. Everything seems to be doing what it should except for the chimes. We are going to the beach today to have a bit of a play and there is a very steep and loose hill along the way íf I make a bit of a detour so I will have a bit of a muck about there too. Perhaps Im missing something.
Çheers, Rick.

Thinking about it, the mode switch test isn't 100% conclusive. While the mode switch test will verify the hi/lo switch is working and has continuity to the Auto ECU, it doesn't actually verify the connection to the SLABS ECU is ok.

The M & S lights are controlled by the Auto ECU, while HDC is a function of the SLABS ECU. Both of these ECU's are connected to the hi/lo switch, but pass though different connectors and headers along the way.

If you are still having issues with HDC after your trip it would be worth checking the wiring to the SLABS ECU.

Ultimately the easiest way to check is with a Nanocom as this will allow you to check if the SLABS ECU is seeing the change of state of the hi/lo detect switch.

cheers
Paul

Now that I think back I had the same problem/symptoms once. I removed the connector from the high low switch on the transfer case and sprayed it and the spade terminal of the switch with contact cleaner and then with lanotec and then slid it on and off a few times and made sure it was securely on, and no more problem. Because as said above the HDC will only come on in low range (well...except where modded like mine to retrofit CDL and that switch then became the one to illuminate the dash light for CDL and I have a separate dash switch that when pressed tells the SLABS ecu I am in low range...but can do that now in high range which is a nice 'feature' and allows me to cycle the ABS pump much easier using HDC).

You would also notice a lack of aggressiveness in the traction control if the switch was not working because the ETC gets angry when in low range.

Cheers

Well I have to back track on my previous post a little. Before we left this morning I went into the paddock beside the house and went through the motions of selecting low range, mode switch and lo and behold, the manual light failed to light up and the sport mode light was still on.
I checked again to make sure things were where they should be and went through it once again. Still the sport light when there should have been the manual light. So I guess my next step is to check the connections from the switch as Paul suggested and then go on from there.
Looks like a Nanocom is on the shopping list too.
We still went for a bit of a drive to the beach and down one of the feeder creeks. Managed to get the ETC light illuminated a few times on a bit of a step up out of the creek but then went round and did it again with the CDL engaged and it sailed right up.
Cheers, Rick.

Rick,

If the high/low detect switch hasn't been working then you are in for a treat when you get the issue fixed

Check out the switch and connectors under the car first. If the problem doesn't lie there report back and I'll post up some more material that will help you check the cabin wiring.

cheers
Paul

Thanks Paul. I'm at work for a few days now but will first check the switch wiring and then the switch first chance I get. Hopefully I can sort it out relatively easily. My son (a Toyota fanatic) tells me that we are off to the Coffs Harbour hinterland and the VIC high country in April/May (I hate the cold) so I have a bit of time to sort it out. Having said that, a group of off road fiends from work are planning a trip along the CREB track (can be done as an overnight return trip from here) before the wet sets in and they close the track. It would be nice to sort it out before then.
Whatever, I am more than happy with my D2a.
Cheers, Rick.

Hi Paul,
Had to take out the front shaft recently to replace the double cardian joint and as you probably know, that makes it a whole lot easier to get to the high/low detect switch.
I checked the plug first and gave it a clean but nothing changed so I went to check the continuity of the wiring when low and behold one of the wires simply fell out of the switch body.
Sourced a new switch and installed (after rewiring as it had the wrong plug on it) and then reinstalled the front shaft and now we HAVE HDC and no annoying fault chimes.
Pretty simple solution. It would have been done sooner if the switch was easier to get at.
Now I am waiting for a new injector loom to arrive so that I can replace it (first signs of oil in red ECU connector) and will also replace XYZ to stop it dropping into limp mode on the highway.
We have just come back from Fraser and had a great time with a bunch of Toyotas that thought it would be fun to outshine a Disco. None had any success and one 100 series took the time to dig himself out of a sand bog rather than get snatched out by a Landrover. We all enjoyed a beer or two while he sweated with his shovel.
Off to do the CREB, Starcke and Laura/Maytown coach road in a few weeks and I'm sure the HDC will show me what it can do in some of that country.
Cheers, Rick.