Hi all,

I performed the Option B bypass on my 2003 Discovery II last weekend hoping to resolve the Three Amigos, but unfortunately, all three lights are still illuminated.

My mechanic friend connected his professional scanner (a capable unit, but not Land Rover specific like a Hawkeye or ABS Amigo). It reads the ABS shuttle valve fault code, but despite multiple attempts, the code absolutely refuses to clear.

This leaves me wondering:

* Is it likely I made an error in the Option B wiring or soldering?

* Or, is it essential to use a specific tool like the ABS Amigo or Hawkeye to clear these particular faults, even if a generic pro-scanner can read them but fails to clear?

I ask because the code's refusal to clear makes me unsure if my bypass was successful. I've gone ahead and ordered a replacement ABS shuttle valve module, thinking I might need to install that instead. However, before I go through with the replacement, I wanted to confirm: Does this inability to clear the code strongly point to a bad bypass, or could it simply be that I must use one of the LR-specific tools for the reset to take effect?

Any insights or similar experiences would be greatly appreciated!

Thanks.

 

I would use a multi meter to check the wiring. Definitely possible some connections are not that great. Check the ground, and then I think there is some resistance measurement you need to have which changes when one of the valves is pressed and its a different number when both are pressed. Otherwise try unplugging the battery. This might clear the code. When I did option B I didn't have to clear anything and it worked first try.

 

Yeah, sounds like you did not get it fixed. Option B is a circuit through two switches, pressing the switches changes the resistance. Probably some good threads on it.

 

Thanks @evil_goat and @Extinct – you are likely right that my Option B wiring is the culprit.

Thinking back, the ohm readings were unstable when I tested the switches after soldering, which should have been my clue. I suspect using a small torch lighter instead of a proper soldering iron resulted in a poor solder joint.

That explains why the code won't clear – the electrical fix isn't actually correct. It looks like I definitely need to redo the wiring properly, either on the original part or the new module I ordered.

On a related note, when removing the electrical module attached to the modulator block (the part is held by 3x small hex head screws (size 4mm if I remember correctly)), I had trouble with my own hex bits potentially stripping the screws. My friend had a set where the bit ends seemed sharper or less rounded, fitting more precisely. Can anyone recommend a specific brand or type of high-quality hex bit set known for having sharp, precise tips that work well on these small, easily damaged screws?

Thanks again for all your insights so far!

 

When you perform Option B it is critical to get a good ground. If the ground is no good = Option B will not work Also did you cut the old lead off the shuttle valve switches? Cut that off, attach your 2 wires, one goes to ground, and the other goes to the vehicle side of the harness on the Yellow/Green wire. If the scantool cleared the codes properly upon startup you should just get a single ABS fault light. Then once you move and the ECU detects the wheel sensors that light goes out.

 

I remember using a hex bit meant for a screwdriver and putting it in a 1/4 socket. Worked way better than the hex keys I was trying to use. But its very easy to lose the bit. I used crimp connectors instead of soldering. To test, connect one wire of the multi meter to the ground wire (or even better a grounding point on the car to ensure that your ground is good) and the other lead on that one yellow/green wire. Take the shuttle switch out, and with both valves pressed, you should get 1k ohms, one pressed 2k ohms, and none pressed 3k ohms. If you are certain your wiring is correct it is possible that the shuttle valve switch has failed.

 

Thanks for your observations.

1. Point taken on the ground importance. I used the steering reservoir holder bolt ground point shown in the Option B step-by-step guides. Checked continuity, but I guess I will have to sand it to bare metal and check resistance to ensure it's solid, as suggested? or is there another suggestion to obtain a better ground contact there? Should i treat it after to avoid rust in that area?

2. Yes, the old connector was cut off and those two wires went to those two places (ground and that yellow/green wire).

I will try to see if after trying to get better ground this does not get resolved and if not I will use the newly delivered replacement switch assembly and will install it, I have tested it without the mod and the Ohms check to spec.

Will revert with outcome.




Thx for the suggestion, since i have the new part and it comes with screws i will try to see if any of my screwdriver hex bits fits in those tighter before i attempt to use the bits on the installed part.


Thanks for the hex bit tip (using a driver bit in a socket) - sounds much easier.

Good idea to test fit the bit size on the new screws before tackling the old ones.

Also, thanks for confirming the ohm test procedure. The new switch passed that test, confirming the old one likely failed.



Will try to tackle this during the weekend and revert.

 

** SOLVED **


Hi all. First, a big thank you to everyone who offered comments and suggestions


I'm happy to report the Three Amigos are gone! The issue turned out to be the shuttle valve switch assembly I had previously used for the Option B bypass.


This weekend, I installed a new replacement shuttle valve switch assembly, setting it up for Option B after confirming its resistance readings (~1k, ~2k, ~3k ohms) were correct per the procedure before installation. I swapped out my previous Option B wiring/switch with this new one, cleared the codes, and it worked perfectly.


Upon testing the old switch assembly I removed, I found the resistance readings were indeed inconsistent and incorrect.


KEY TAKEAWAY: If you are doing Option B, definitely test the resistance of the shuttle valve switch assembly thoroughly before wiring it in. If the readings don't match the specifications precisely, the switch itself is faulty, and the bypass won't work.


Happy to be driving without that trio of lights!

 

Thanks for posting the resolution!