Code C1737 on LX570- “Check AHC” light on

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RiDE

RiDE

10 Year
Joined
Mar 24, 2012
Threads
12
Messages
123
Location
Portland, OR
Website
www.tighttacos.com
Anyone know what part needs to be replaced? My AHC is currently disabled because of this code. I’ve tried clearing it and as soon as I drive for about 5 minutes, the light kicks back on and AHC disables. Fluid levels in the AHC reservoir are within spec. Hoping this is something I can figure out before going to Lexus.

It is showing C1737 “FL Gas Spring Switch Valve” in Techstream.

This is on a 2010 LX570.

Thank you in advance for the help

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Front Left Valve

Probably this one on the front left...

FL-valve.webp


You might check all your connections fist.
 
Ain't a great one to have:

C1737​
When either of the following is detected:
  • With the spring rate switch valve LH not activated, an open signal of the spring rate switch valve LH is detected for 1 second or more.
  • With the spring rate switch valve LH activated, a short signal of the spring rate switch valve LH is detected 8 times successively.
  • Harness or connector
  • Front suspension control valve LH (Front spring rate switching valve LH)
  • Suspension control ECU
  • No. 1 height control valve


(a) Turn the engine switch off.
(b) Connect the Techstream to the DLC3.
(c) Start the engine and turn the Techstream on.
(d) Enter the following menus: Chassis / AHC / Active Test.
(e) Check the operation of the front spring rate switching valve solenoid when operating the solenoid with the Techstream.
AHC

Tester Display​
Test Part​
Control Range​
Diagnostic Note​
FR Gas Spring Switch Valve​
Front spring rate switching valve RH
ON or OFF​
When the FR Gas Spring Switch Valve item of the Active Test is operated, the FR Gas Spring Switch Valve item of the Data List changes to ON/OFF.
FL Gas Spring Switch Valve​
Front spring rate switching valve LH
ON or OFF​
When the FL Gas Spring Switch Valve item of the Active Test is operated, the FL Gas Spring Switch Valve item of the Data List changes to ON/OFF.
OK:
The front spring rate switching valve operates.
 
AHC delete recipient!
 
hickuptruck said:
AHC delete recipient!
Click to expand...
Why? Occasionally a part goes wrong, no need to throw out the whole suspension . . . it isn't 'cheaper' to replace with springs, and once you do, you still don't have height adjustability.
 
Awesome @nwfl4runner for posting that debug info. The community here is just awesome.

Best of luck to the OP and let us know what you find. There's so little information on these boards to fixing AHC things as it's been so solidly reliable. I can count on a couple hands the real number of issues reported here. Compared to the endless non-AHC suspension swap this/broken that threads.
 
It ended up being a super simple fix. The plug somehow worked itself loose. All I did was push the plug back in and ahc is now working with no issues. Mind boggling.

I definitely have no plans of ripping the AHC out. I love its features and functions. I actually have brand new OEM spare shocks all around for when the time comes to replace them. Previous owner purchased them and gave it to me when I bought the truck.

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