Finally got my LX back up and running, I'll detail my issues and fixes here in case it helps somebody else, and for my own reference. Sorry for the long post!
In May I acquired a 2010 LX with 140k miles (225k kms) and a full dealer service history. The dealer had flushed the AHC system at 87k miles, and the seller reported he did a DIY fluid flush a couple of months prior to the sale.
In June it threw a C1755 (Rear Gate Valve) code the first time I ever tried to put it into High. I cleared the code in Techstream, and the vehicle went into H as expected. The code sporadically came back and prevented use of AHC until I cleared it. A couple weeks later, while I was driving with the check 4 Wheel AHC light on, a chime rang and the ride quality rapidly deteriorated. I limped it home and found I now had the C1763 Abnormal Pump Pressure code as well.
After doing some basic diagnostic work, lots of reading on MUD, and having a bunch of fluid shoot back out of my pump while fiddling with the Active Tests, I zeroed in on the AHC pump. Turns out the pump wouldn’t operate even when hooked up directly to a charged 12v battery. Additionally, Rear Height Control Tube No. 6 had a seized flare nut, so I ordered the pump from Japan on ebay, and Rear Height Control tubes 4, 5, and 6 from Partsouq. I picked up 3 aluminum cans of AHC fluid from my local Lexus dealer.
All of the hydraulic line fittings were seized except fortunately the terminal end of No. 4, I took the exhaust off of a few hangers and passed a long handle ratchet over the muffler and used a mirror to see the banjo bolt. Also once I disconnected one end of No. 5, which passes over the exhaust, it immediately snapped in the known weak spot by the heat wrap. Glad I ordered all 3 tubes!
I never found a clear answer regarding how to prime the new pump. What I did was I filled the reservoir with new fluid to approximately the Min line on the bench. I hooked it up to a 12v battery with clear tubing attached to the outlet. It took less than a second before I saw fluid being pushed out of the outlet, so I considered it primed. I removed the tubing and plugged the outlet with the rubber plug that the pump shipped with. I bolted up the pump, removed the rubber plug and connected the No. 6 tube and topped up the reservoir to a little above the Max line (new fluid, inline filter in place).
My 6 year old battery was completely dead after sitting for several weeks, so I bought a replacement.
Once everything was installed I started the vehicle with Techstream running. The C1763 code immediately appeared. I cleared the code and it returned within 2-3 seconds, but I heard the new pump run for those 2-3 seconds, which hadn’t happened with the old pump. I cleared the code again, the pump instantly started running, and the code never came back. I hopped out of the vehicle and watched the reservoir to ensure the fluid level was dropping, but not at risk of running dry. After a few seconds I noticed the vehicle beginning to lift to N.
I topped up the reservoir and bled the system. Lots of air in the front left, incrementally less air as I moved through the remaining corners. Topped up the reservoir, took it for a test drive, cycled through L-N-H no problem. Overnight I noticed fluid had dripped from the bleeder screw on the Accumulator which I had loosened while trying to diagnose the problem. Tightened it, considered it bled, topped up the reservoir, and bled all 4 corners again. Still substantial air in the FL corner, but not as much as the first time. Topped up the reservoir, and that’s where I sit today. Everything works, and no codes.
I plan to disassemble the original pump at some point to see if I can at least form a theory regarding what the problem was.
In May I acquired a 2010 LX with 140k miles (225k kms) and a full dealer service history. The dealer had flushed the AHC system at 87k miles, and the seller reported he did a DIY fluid flush a couple of months prior to the sale.
In June it threw a C1755 (Rear Gate Valve) code the first time I ever tried to put it into High. I cleared the code in Techstream, and the vehicle went into H as expected. The code sporadically came back and prevented use of AHC until I cleared it. A couple weeks later, while I was driving with the check 4 Wheel AHC light on, a chime rang and the ride quality rapidly deteriorated. I limped it home and found I now had the C1763 Abnormal Pump Pressure code as well.
After doing some basic diagnostic work, lots of reading on MUD, and having a bunch of fluid shoot back out of my pump while fiddling with the Active Tests, I zeroed in on the AHC pump. Turns out the pump wouldn’t operate even when hooked up directly to a charged 12v battery. Additionally, Rear Height Control Tube No. 6 had a seized flare nut, so I ordered the pump from Japan on ebay, and Rear Height Control tubes 4, 5, and 6 from Partsouq. I picked up 3 aluminum cans of AHC fluid from my local Lexus dealer.
All of the hydraulic line fittings were seized except fortunately the terminal end of No. 4, I took the exhaust off of a few hangers and passed a long handle ratchet over the muffler and used a mirror to see the banjo bolt. Also once I disconnected one end of No. 5, which passes over the exhaust, it immediately snapped in the known weak spot by the heat wrap. Glad I ordered all 3 tubes!
I never found a clear answer regarding how to prime the new pump. What I did was I filled the reservoir with new fluid to approximately the Min line on the bench. I hooked it up to a 12v battery with clear tubing attached to the outlet. It took less than a second before I saw fluid being pushed out of the outlet, so I considered it primed. I removed the tubing and plugged the outlet with the rubber plug that the pump shipped with. I bolted up the pump, removed the rubber plug and connected the No. 6 tube and topped up the reservoir to a little above the Max line (new fluid, inline filter in place).
My 6 year old battery was completely dead after sitting for several weeks, so I bought a replacement.
Once everything was installed I started the vehicle with Techstream running. The C1763 code immediately appeared. I cleared the code and it returned within 2-3 seconds, but I heard the new pump run for those 2-3 seconds, which hadn’t happened with the old pump. I cleared the code again, the pump instantly started running, and the code never came back. I hopped out of the vehicle and watched the reservoir to ensure the fluid level was dropping, but not at risk of running dry. After a few seconds I noticed the vehicle beginning to lift to N.
I topped up the reservoir and bled the system. Lots of air in the front left, incrementally less air as I moved through the remaining corners. Topped up the reservoir, took it for a test drive, cycled through L-N-H no problem. Overnight I noticed fluid had dripped from the bleeder screw on the Accumulator which I had loosened while trying to diagnose the problem. Tightened it, considered it bled, topped up the reservoir, and bled all 4 corners again. Still substantial air in the FL corner, but not as much as the first time. Topped up the reservoir, and that’s where I sit today. Everything works, and no codes.
I plan to disassemble the original pump at some point to see if I can at least form a theory regarding what the problem was.
