 | Home > Td5 > 2000 TD5 Defender - Handbrake/Brake Fluid Light Not Working |
 
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6626   
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The black/white wire provides the ground path to illuminate the LED in the panel.
So grounding the black/white wire by using the handbrake switch, when the fluid level float drops or the ABS system grounds it will cause the lamp to come on. However the lamp is always on by default, and has to be extinguished first - on ABS Defenders this is done by the ABS ECU, on non ABS vehicles there is a wire loop to “pull up” the black/white wire to 12V, which switches off the lamp ready for it to be switched on by the handbrake or fluid float. As the ABS system has been disabled, then you might well find that someone has messed about with the actual warning lamp panel itself and removed the LED or otherwise broken the circuitry to the lamp. If you’re lucky it might have been messed with at the wiring to the warning lamp panel, have you had the instrument binnacle off to have a look?  1988 90 Td5 NAS soft top
2015 D90 XS SW |
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14th Jan 2025 9:43pm |
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| rgh.key Member Since: 14 Jan 2025 Location: Stoke on Trent Posts: 14 
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Thanks for your reply, so I think the ABS ECU was disabled due to the Pump Return Relay base been corroded so badly that the 12V feed had literally detached and was floating around in the underseat box not ideal! Especially when it’s constant 12V off the battery. I’ve repaired this and got the relay all back into place, just need to replace the ABS ECU fuse now to see what happens, a little apprehensive about doing this as I don’t want to break anything further as the Defender drives and stops perfectly well, just has no Brake, ABS or TC light when starting up which I imagine would be an MOT failure even though the seller managed to get a 12 month ticket back in December 2024 (1 month ago!)
Anyway reading through the WABCO manual for the ABS ECU this states: “Brake warning LED: This turns on the brake warning lamp for 20 seconds. The brake or • EBD lamp is a combined warning lamp with the low brake fluid warning and the handbrake warning lamp. The lamp is a red light with an exclamation mark inside a brake symbol. The ABS ECU will illuminate this light if it senses a fault that will affect its ability to control the braking balance of the vehicle. This lamp will be illuminated for 3 seconds when the ignition is switched on, as a bulb check function. It will then extinguish as long as no fault currently exists that may effect the operation of the EBD. The EBD warning lamp will remain illuminated if the ABS ECU is in "new-born" mode. Unlike the ABS warning lamp, the ABS ECU supplies a voltage to illuminate the light, not to turn it off. Modes of operation: ⋅ No lamp and no audible warning indicate that the ABS/EBD/TC and HDC systems are OK. ⋅ The lamp being on could indicate that the ignition has just been turned on (Bulb check for 3 seconds), the handbrake is on, there is a low brake fluid level, the ABS ECU supplied voltage is much too high or much too low‚ there is a new-born ABS ECU fitted, the ABS has a sensor/pump or valve fault logged for this journey. ⋅ Both lamp on and the audible warning indicates that the ABS has detected a sensor/pump or valve fault.” Interestingly in particular is the section “Unlike the ABS warning lamp, the ABS ECU supplies a voltage to illuminate the light, not to turn it off.” which would imply that the ABS ECU does supply the 12V signal into the circuit. What I am struggling with on this circuit is where is the 12V supply coming from into the circuit in order to power the lamp, the lamp itself is references to ground so it needs a 12 V supply to illuminate, when measuring at the Hand Brake Switch and the Brake Fluid switch there is no 12V supply to these devices? Is there something I am missing or is it indeed the ABS ECU been off that’s causing this lack of voltage. Also worth noting the 2002 models actually work differently in the fact that the 12v supply is found in the warning lamp and simply gets switched to earth making the lamp light through the handbrake or brake fluid lamp, the 1999 wiring diagram is completely different. 1999MY Instruments Click image to enlarge 2002MY Instruments Click image to enlarge [/u] |
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14th Jan 2025 10:16pm |
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6626
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1999MY diagrams are incorrect for the instruments. They are wired as per 2002MY diagrams.
1988 90 Td5 NAS soft top
2015 D90 XS SW |
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14th Jan 2025 11:02pm |
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| rgh.key Member Since: 14 Jan 2025 Location: Stoke on Trent Posts: 14
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Hello Martin,
Are you sure? I found the updated version of the 1999MY Instruments on here that was updated some years ago, however, looking at the update which is the version I have been using in my fault finding it would appear that only the second page has been altered, the first page which is where the Brake Warning light is show has not been changed and still has the bulb referencing to Ground, this would also mean that the WABCO documentation was also incorrect in stating that the ECU provides the 12V to turn on the lamp and not switch it off? 1999MY Updated Instrument Drawing Note: Positive 12V feed C0230-1 is only shown feeding from Engine Management bulb onwards, Handbrake and Low fluid are still depicted as referencing earth via C0230-8 Click image to enlarge Are you saying that the updated drawing is also incorrect? I got this information from this source: https://www.web-rover.co.uk/nav.php?p=td5kb/ecderror |
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15th Jan 2025 7:03am |
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6626
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That's my corrected 1999MY drawing (look at top right!)
 
You have spotted something I missed though. 100% the brake warning light is a switched ground, on all Td5s (on all Defenders actually). I'll get a corrected version of the corrected diagram done  1988 90 Td5 NAS soft top
2015 D90 XS SW |
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15th Jan 2025 9:27am |
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6626
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In the meantime, use the 2002MY diagrams as these are 99.9% 80% correct for the warning lights.
The error on the 2002MY is that the Black/White wire to C0230-14 on is labelled as "(ABS)" when it should have no label (that connection is on all Td5s, ABS or not). Edit: revised down 1988 90 Td5 NAS soft top
2015 D90 XS SWLast edited by Martin on 15th Jan 2025 12:42pm. Edited 1 time in total |
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15th Jan 2025 10:16am |
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| rgh.key Member Since: 14 Jan 2025 Location: Stoke on Trent Posts: 14
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Thanks for clearing that up, thats very interesting, I have no 12V signal at either the Brake Fluid Level or at the Handbrake Switch so I wonder if the LEDs are physically dead in the cluster or have been removed, the wiring looks to be untouched, however, if the unit was meant to have ABS and now has this powered down I wonder how I have not got the ABS and TC lights on if the ABS ECU is referencing these to ground. I have checked the connector at the back of the instrument cluster and there is definitely a Green/White cable in Pin 1 of C-2030 which is the 12V signal that is used for all of the lamps of which some are working correctly, for instance the Oil Pressure Light works correctly (J115) which looks like its fed from the 12V feed C0230-1 so I must have 12V present for that to work.
Starting to think it may be an issue in the header 0288 which is where the 12V will be distributed to the ABS ECU, Handbrake and Fluid Level. Going to have to get my Multimeter back out and start testing at some points, still can't understand why the WABCO unit documentation mentions that the bulb is powered on and not turned off, that does actually fit with the current drawing. It would seem this is just a multitude of mistakes in the documentation... |
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15th Jan 2025 11:23am |
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6626
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You *might* be missing the 12V supply into C0230-1 (16 pin warning lamp panel).
If you look at the 2002MY diagram, this claims this supply is for the Brake/ABS/TC/Gear Temp lamps only. The other ignition supply to C0233-16 (20 pin) is apparently used for supply side of low fuel, oil P, alternator and difflock. Check for 12V on the white/green wire to C0230-1. If that is OK, I would start thinking that the internals of the warning panel have been bodged to cover up a removed ABS unit. It would be a huge coincidence to have a fault at the header connector causing this issue, whilst also having a disconnected/disabled ABS system done by a previous owner... 1988 90 Td5 NAS soft top
2015 D90 XS SW |
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15th Jan 2025 12:15pm |
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6626
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You've sent me down a right rabbit hole on this!
Turns out the 2002MY diagrams are wrong AS WELL, but for different lamps - the MIL, Glow and Engine Immob are wrong. MIL and Glow are ground switched, so have a 12V reference not Ground as on the diagram. Engine Immob reference is 12V ignition not 12V permanent from the speedo connector C1060-9 as pictured. 1988 90 Td5 NAS soft top
2015 D90 XS SW |
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15th Jan 2025 12:45pm |
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| rgh.key Member Since: 14 Jan 2025 Location: Stoke on Trent Posts: 14
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Haha! I am sorry for that, been scratching my head on this one for the past 4 days before actually posting anything, so I have measured the Green/White on Pin 1 of C2030 12V present, I then checked to see if I have continuity between the brake level switch and the black and white cable, which I do! so I know the circuit is all okay, however, still no lights on the dashboard!
So I set about dismantling the light unit to see if I could see if any cowboys had been in there and to my surprise look what I find! Click image to enlarge Click image to enlarge Some lovely person has put electrical tape over the Brake Warning Light, ABS Light and TC Light! When I put the ignition on I get the Brake Warning Light and TC Light now on constantly, interestingly I do not get the ABS light which I was expecting although with the ABS ECU having no power this may be caused by that, however, I think I may have rectified the fault the the ABS, so hopefully this will be back in business. I shall start another post about that so not to muddy the waters in this one! |
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15th Jan 2025 3:16pm |
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| 4RF RDS Member Since: 19 Jul 2015 Location: Ottawa Posts: 950  
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🤦🏼♂️. That is one way to fix warning lights being constantly on🙄. The three amigos being lit is due to your ABS module being disconnected and or not working. 2010 Range Rover MkIII Autobiography Super Charged (Idris)
2003 Range Rover Mk III (Desmond FitzWilliam) 2000 Defender 110 CSW TD5 (CTX) 1992 Range Rover Classic (Lizzy) 1972 Series III 300 Tdi (Stanwood) 1967 MGB GT Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin to slit throats. H. L. Mencken (1880 - 1956) |
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15th Jan 2025 5:22pm |
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| rgh.key Member Since: 14 Jan 2025 Location: Stoke on Trent Posts: 14
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Haha it certainly is the bodge it and scarper approach that’s for sure, not exactly sure what I have purchased
The ABS ECU has its fuse removed, I’m detailing that fix in a separate post I’ll be sure to link it to this one so you can see the other gems the previous have left me with
ABS Post for anyone interested: https://www.defender2.net/forum/post1057480.html#1057480 |
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15th Jan 2025 6:02pm |
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