New user here! If I'm going to keep this thing, I'll need all the help I can get. Recently purchased my '05 LR3 and after about 6-7000 miles, I've started to have issues with multiple warning lights: transmission fault-HDC-suspension lowered. Of course, my suspension has lowered to access height and will not rise because of these warnings. I did my due diligence on the web, mostly here, and came up with some info. To jump ahead just a bit, I finally got the codes read today and the only one thrown was P0504 "brake switch a/b correlation". In addition, this is what i can say for sure. If you depress the brake pedal while starting and hold it, the warnings do not appear. However, as soon as you release the brake pedal, the warning lights come on. I've already replaced the switch and cleaned the crap out of the plug wire connector that snaps into it. I've had the battery and alternator tested and both are good to go. I pulled the four rear bulbs (two brake and two driving) and the results are the same. I did not pull the high brake, but it does work, as do all the other lamps. One of the rear driving bulbs is an 1157 and one is a phillips 21/5, as are both of the brake bulbs. I also tested the voltage on the red wire going to the brake switch and only got about 6.4v, which seems awfully low. When the key is on, the red wire has no power with no brake and power when brake is depressed. When the key is off, it is the opposite. If I did it correctly, this wire is supplied through fuse #66 (the DSC?). I pulled the fuse and tested across it's block and got 12v+. To wrap it up, I'd appreciate any info on how to diagnose the switch and the harness going to it properly, as well as anything else that might be pertinent to my situation. Thanks to all in advance!

 

The link below is to a number of brakeing system related files.

I see you changed out the brake switch so that is good. It apparently did not might solve the problem, but even if not, a new switch will solve future problems.

Also replace all your rear bulbs with genuine, and maybe also the front signal light bulbs as well. For trouble shooting purposes, remove all of them, (seems you did however), or disconnect the headlight and tail light connectors and see if the problems are reduced. Also remove the backup light bulbs as a grounding concern can backfeed thru the backup light bulbs.

Also electrically, a 1157 is very different than a 21/5 per the bulb file within the link. Even if they were factory spec bulbs rather than far east sourced, the mismatch is a problem.

I agree, do not worry about the high mount as it is LED and does not seem to cause problems - for some reason.

DISCO3.CO.UK Photo Gallery - Brake Light Switch Replacement

I expect the fix is a simple one - but finding the problem, typical Land Rover, near impossible.

Note my comment in the files attached where I say the problem is the two pair of contacts within the brake light switch; the low amps contacts to the ABS/DSC and the relatively high amps contacts to the brake lights.

That low voltage number puzzles me by the way - suggests a ground concern or you are measuring the anti skid contacts rather than the brake light contacts.

In the link, there is a brake light wiring diagram you can print that shows the two sets of switch contacts. The antiskid is Normally ON and the brake light Normally OFF. That is power flows thru the antiskid contacts when you are not on the brakes and power stops flowing when on the brakes. The brake light contacts are of course the reverse of that.

 

bbyer, thanks for the reply. You mentioned removing the bulbs from or disconnecting the headlights to eliminate lighting as a cause. Could the headlights indeed cause this problem I'm having? Regardless, I will go through and disconnect all to test again and then replace everything with OEM bulbs. Also, it's worth mentioning that I did pull the battery to access the transfer case module. I pulled the harness' there, as well as all the surrounding ones I could see, and cleaned everything with contact cleaner and a brush. Let it dry and reconnected, but still got same result. Is it possible that this module is the source and needs to be replaced? If so, is there programming involved, or is it plug and go? Lastly, does the absence of the faults when starting with the brake depressed and their immediate return when the pedal is released help narrow the search at all?? Thanks!!

 

Re the headlights, what I was really meaning was just to disconnect the big connector re each assembly. For testing purposes, that is an easy way of getting all the front bubs out of the circuits; same for the rear, except that pulling the bulbs in the rear is alot easier than the front where you have to sort of disassemble the works.

I wonder if you are on to something regarding foot on the brake and all seems well.

When your foot in on the brake, the contacts feeding power to the ABS are open. I see you pulled F66P and tested for power, but have you tried running the engine with F66P removed?

I am not ready to blame the transfer case module yet.

Also when your foot is on the brake with the engine running, and no nasty lights, are you in Park? If so, try shifting into N and D. If still no red/yellow lights, engage the Hill Decent yellow button. If still no lights, the tranny module is probably OK and it is something to do with the ABS wiring - still a problem but ...

In a perfect world, with F66P removed, the only warning lights and messages you would see would be related to the ABS; the air system should function, (at least normal height); cruise control and downhill probably not, but most else would seem fine.

Well we dream!

 

When i start it with the pedal depressed, I get no faults. And yes, I can put it into N or D and still get no faults. I can even go down the road, but the tranny doesn't want to shift with my foot still on the brake, so as soon as i release it, the warnings pop up. I'll try the fuse removal and run today, thanks!!

 

Could this be a simple fix with a transmission capacitor going bad ?

 

I assume you mean what I call the radio noise suppression capacitor per the link below.


It is a good question but normally when the capacitor goes defective, 10 amp fuse F30E blows and while the engine will run, there are no gears at all and your 3 will not move.

This is a real show stopper and the reason I installed a new capacitor as preventive maintenance, but in this case, I do not think it is a problem.

It would sure be a simple fix if it was.

Actually as an experiment, one can get under the 3 and disconnect the wire to it located on the tranny on the passenger side.

The reality is the capacitor is one of those parts that is probably installed to satisfy the FCC; the engine will run just fine without it; the tranny will not shut down due to a blown fuse and no power to the tranny computer plus the radio will continue to work just fine.

DISCO3.CO.UK Photo Gallery - ZF 6HP26 Automatic Transmission in LR3/Mechatronic Replacement Hints plus drains for steel and plastic pans

 

Yes Bruce, I meant radio noise suppression capacitor.I think , he stated , that he can not get transmission to move, but maybe I did not fully pay attention to a explanation of the problem.
I assume , that you let somebody else to change a little radio noise suppressor and have a headache doing that, as I just learned, that replaceing it on the driveway is no picnic .Harness and screws holding the unit lay directly behind gearbox level pivot and it is a royal pain to get to them altogether .I had better access to front air strut nuts on top of each tower, than this little pesky plastic box!

 

I just reread the posts and now I do not know if the 3 is mobile or not. I figured it was but now that I reread them, maybe just the engine works.

You guessed correctly; I had the LR dealer change out the capacitor during one of my routine oil changes.

That sort of explains why an oil change seems to always cost me about two thousand as I add in some other minor item that well, as you explained, is not minor when you go to actually do it.

I think the reason everything is so difficult to replace on the 3 is because LR drops the body on to the frame right at the end of the production line. Normal body on frame vehicles these days have the engine tranny combo slipped in prior to the hood going on, but with LR, everything is mounted except the steering column as it is with the body.

Per below, Ford used to do that with their model T's but the steering column and wheel were attached. All you needed was a wood box to sit on and you could drive the frame around minus the body. It was a good system back in the twenties.

And I think the nuts on the rear struts are even worse - the air lines sure are.

 

Okay, with the pedal depressed and the vehicle started, tried the following. Pushed HDC button and got no response/no indicator of any kind. Not sure what should be happening when trying to engage it. Tried it in gear and out. HI and LO functions worked w/o issue. Special programs selector **** also worked w/o issue.

Pulled the F66 before starting and driving and got no improvements or further complications. Did not affect loss of air suspension??

Still have to do bulb test.

Reviewed switch wiring diagram. What should the two voltages going thru the switch be?