So you have a green flashing light, and dont understand your 4wd system read here
Here we go!
My green light is flashing when in 2WD all the time when driving. No apparent driving effects noticed. My green light is flashing or permanently lit when driving in 2WD I sometimes get a clunking / whining noise when driving my truck doesnt shift into 4WD when I want it to / flashing light only when in 4WD.
This is the most common problem, caused by people not using 4WD regularly / ever, so to quote the old tale "you dont use it-you lose it"
Troubleshooting, you will need:
Begin by switching into 4h and back a few times, this could free the system up enough to put the light out (unlikely)
Second, crawl under, behind the front wheels to the front diff with the truck running. There will be a rubber cover around a rod which pokes out the back of the diff where the prop goes in this is called your actuator. Peel back the rubber boot at one end, there will be a shiny rod. Now get your mate to shift in and out of 4h, when he does, the rod should move (into the diff in 2h) about an inch. It's more than likely it isn't doing this.
If it is, moving slightly, pull the two vacuum pipes off the diaphragm at the end of the actuator, this is where the screwdriver could be handy, with the pipes off, try and wiggly the actuator rod by hand, with some WD40 in there to ease it up. When you think its moving freely, connect the pipes back up, shift a few times and see if the light goes out.
IF YOUR ACTUATOR SEEMS TO MOVE FREELY WITH PIPES OFF, BUT THERE IS NO MOVEMENT WHEN THE STICK IS CHANGED.
To confirm this, put your finger/tongue over then end of the pipes that come down to the diff. The "front" pipe, which is the one closer to the passenger side, should suck in 2WD, and the other blue pipe should do nothing, visa versa when you switch to 4h. If it only ever sucks from one pipe, or no suck or something similar, its most likely your solenoids have had it. If there is only ever suck coming from one solenoid, an you have already changed the solenoids, and the problem continues. Check solenoid feed section.
To test this, pull the pipes off at the solenoids. (located next to brake reservoir/turbo -old shape) and put your finger over the end, conducting the same test, eliminating the possibility of a blockage in the pipes. If they still do not work as they should (swapping suck from one to the other as the stick is changed) then they have had it 9/10, If you have a multimeter handy you can test the feeds to the solenoids, should read 14v, and 0v depending on 2 or 4wd. (14v in 2h) both feeds should read the same. However this is less likely, more likely to be solenoids.
IF YOUR FEEDS TO SOLENOIDS ARE NOT CORRECT
It could be one of two things. The ECU, or the gearbox sensors. If you know another L200, swap you 4WD ecu for theirs, this is located in the passenger footwell. There are two ECU's the lower one is the 4WD ecu, swap this and see if it fixes the issue.
If you cannot do this, or this hasn’t cured the issue. you will need, a mate, 19mm spanner, torch and a 10mm socket.
Remove centre console around gearsticks. Underneath you will see the transfer case, there are two electrical connections held on the passenger side of the box. These are held by a 12mm bolt and screws in just behind the transfer lever. Undo this, pull up the connections and disconnect, then remove the connections from the bracket. These connectors lead to 2 different sensors located further back behind the transfer lever, the one closest to the lever is the one you need to test. Continuity in 2h and none in 4h ( i think its that way round) if its broken you will find it doesn't switch on and off.
Crawl under behind the box, reach up, and find the sensor at the end of each of the wires, one will be in front of the other. The one towards the front of the truck will need replacing, comes out with 19mm spanner.
IF THERE IS NO VACUUM DETECTED AT ANY POINT? WEAK VACUUM.
To test this, follow the vauum pipes around the solenoids. There will be a T-piece, one to each solenoid, one goes down to a accumulator "coke can" on top of the offside chassis rail, behind the rubber flap in the front wheel arch. One of these will be the vacuum feed going towards the alternator. Test the suck from the feed from the alternator. If this is bad, check all the piping back to the alternator for a hole etc. If this feed is good, but there is nothing coming from the solenoids, pull off the feed pipes to the solenoids, and test the vacuum on these. If there is nothing here either, then connect all pipes. Let the truck run for a minute, shut off the engine, leave for 5 minutes, then pull the pipe off that goes to the accumulator. This should release a strong vacuum that you can hear. If you hear nothing, but the feed from front of truck is good, your accumulator is rusted and has a leak. To confirm this, block off the vacuum pipe going to the acummulator and test again.
IF YOUR ACTUATOR HAS GOOD MOVEMENT, 4WD WORKS AND THE SYSTEM PRODUCES NO NOISE, BUT STILL HAS THE FLASHING LIGHT
There is a 19mm on top of where the rod goes into the diff. With a wire coming from it. Undo the wire , (goes to chassis rail, connector there) then undo with a spanner. Re-attach electrical connection. This will have a push switch on the end which should be shiny, when in 2WD, and the switch not pressed, there should be no dash light. If there is still a flashing light, after you have given the button a few presses to losen it up, you need a new switch. The light should flash when you change to 4h until you press the switch in, then it should stay solid.
If all above is correct, the switch works well, and can be re-attached.
If you still have the problem you need to check the 4WD ecu / gearbox switches and post your symptoms.
Replacement parts can be sourced from Milners, do not get solenoids second hand off ebay, they will likely have not been used either and fail soon.
Written by John Halsey.