Well I’ve had Steve Martin, Chevy Chase, and Martin Short have been up in my place chillin’ and the partying has been real but it’s last call m frs and I’m tired of their **** so...

I’ve been diagnosing according to Land Rover Troubleshooting - Test Procedure And Instructions for Shuttle Valve Switches
and have found no electrical faults so far...

Here are my scanner screen shots:






Then after all the continuity tests showing good, I got this fault:

Any ideas?

 

 

Option B modification is the way to go
ABS Mod - LAND ROVER CLUB V.I.

 

Perform Option B to bypass the weak link inside the Wabco unit. The internal connector that the shuttle valve switches plug into is a common weak link. If you bypass the internal connector with Option B using a nice external connector (looks similar to a 4 wire trailer plug but it's just 2 wires) you cut the yellow/green striped wire back about 4-6 inches from the original plug, tap one side of the new 2 wire connector to the yellow/green wire going back into the cabin/SLABS unit (do not splice into the yellow/green striped wire heading to the Wabco Unit/Plug), and then you take the remaining wire and ground it (HVAC line tie down bolt is a good ground right by the Wabco unit), then at the Shuttle Valve switch side you chop off the connector and splice in the other side of the new 2 wire connector and BINGO job done and you've successfully bypassed the weak internal connection inside the Wabco Unit.

P1590 is a generic ABS fault code and it's triggered whenever there is an actual stored ABS fault (AKA 3 amigo's/3 musketeer's). I'd inspect the ABS sensors at the connectors, and make sure the Allen bolts that secure them are tight and that none of the internal o-rings are floating around in pieces inside the ABS sensor hole causing bad readings.

You can meter out the original shuttle valve switches and use them, but at $45-55.00 it's a cheap part to replace and be done with any Wabco Unit related failures for a long long time.

 

 

Big thing with the repair is a solid ground. If you get the boys after the repair look at the ground and possibly relocating it. I had to do it twice.

 

Consider this kit as part of your repair:
ABS shuttle valve code solution; brake fluid leaks

 

 

well well, looky here:

 

btw it is near impossible to do this without removing the unit on my truck with 240k miles