HVAC problems. 8 codes. HELP (1 Viewer)

[JB2004LC]

I bought my LC knowing the AC was not working. I made a silly assumption that there was most likely a leak in the system or a more basic failed part that would be easy to diagnose. Once I dug into it I found I have 8 separate hvac related codes. They all make reference to the ac amp so I tried replacing the ac amp with one from eBay but that made no change to my problem or codes. Here is the list:
11 room temp sensor circuit
12 ambient temp sensor circuit
13 evaporator temp circuit
21 solar sensor circuit
31 air mix damper position sensor circuit
32 air inlet damper position sensor circuit
41 air mix damper control servo motor circuit (passenger side)
42 air inlet damper control servo motor circuit (passenger side)

Here is what I know that may or may not help diagnose. I replaced the ambient air temp sensor with a new Toyota part so I know it is good but the outside temp still reads as - -. The vents seem to blow hot air regardless of the temp setting but the passenger foot well area blows cool (outside temp) air no matter the settings when it was cold out. All of the fuses have been checked.

Where do I start? What, if any, codes are related or would cause other codes? Any pics of FSM wiring diagrams and diagnostic procedures would be appreciated! Also, I am not sure where all the hvac parts in question are located. I’ve been in the dash behind the nav unit multiple times now. All plugs and wiring there seem ok visually.

Thanks for ANY help!

 

[TXSunDevil]

Here is the EWD from a 2006 but they should be almost identical. Looks like they all share some wiring.

 

[TXSunDevil]

 

[JB2004LC]

View attachment 1690344 View attachment 1690345 View attachment 1690346

Thank you for the FSM info!

 

[JB2004LC]

Are there any Toyota techs on the forum?

 

[JB2004LC]

Update: The LC has been at the dealership for almost 2 weeks and they can’t figure it out. They wanted to replace the AC amp at $700 but I told them I had already tried a used one and that didn’t change any of the codes. They dug around a bit longer and now they say they don’t know anything else they can do other than replace the AC amp.

@flintknapper
You seem knowledgeable on our AC system as i’ve seen you assisting others on AC threads. Any ideas on what direction I should go?

 

[TXSunDevil]

Do you have a good auto electrical shop in your area?

 

[PADDO]

@JB2004LC Have you cleared the codes by pulling the ACC fuse in the LH footwell? AC diagnostics says you need to pull this fuse for 10+ seconds to erase the DTCs in memory.

 

[flintknapper]

@JB2004LC Have you cleared the codes by pulling the ACC fuse in the LH footwell? AC diagnostics says you need to pull this fuse for 10+ seconds to erase the DTCs in memory.

^^^^^ Yep. Start here.

 

[JB2004LC]

I’ve pulled the ACC fuse and unhooked the battery. Each time the same 8 codes come up.

 

[JB2004LC]

Trying to find some time to dig back into this...
@planomateo have you ever seen these 8 codes together at the same time? Any idea where you would start?

Since originally posting I have found out through the Toyota service website that the LC was in the dealer multiple times for AC problems before I purchased it. The AC amp was replaced TWICE! It appears it may have fixed the AC temporarily each time but then failed again at which time the vehicle was most likely traded in.

 

[planomateo]

From 2007 LC manual. I haven't looked through the wiring diagram on this, but I'd look for something that connects all of these together.

There really is no commonality between the below trouble areas across all 8 codes, perhaps it's multiple issues or perhaps it's a central control issue like an ECU or control board.

 

[planomateo]

 

[y5359]

Does anyone have an experience with codes 21 and 41 what needs to be done to fix them? A little background on my 06 LX470. When I got the car the AC worked but it would not switch to heat. I took it to a mechanic and now the heat works but can't get it to switch back to AC.

 

[AstRomroMan]

Did you ever figure this out?

 

[y5359]

Did you ever figure this out?

Not yet I believe it is the servo motor by the passenger foot-well but I have not been able to get the plastic duct piece off to get access to the motor to test it.

 

[JB2004LC]

Does anyone know where or how the AC amplifier is grounded? After spending some time in the FSM it looks like most of my codes share the A46 plug ground at pin 18 at the AC amp. The FSM says A46 - 18 goes to a Body Ground but I can’t find info on where that is? Any ideas? I’ve ordered a EWD but have not got it yet. Maybe that will help me?

 

[BamaHeel]

Not yet I believe it is the servo motor by the passenger foot-well but I have not been able to get the plastic duct piece off to get access to the motor to test it.

Everyone says that servo is a job but in my experience it is a huge PITA to reach the tiny screws.

Had to replace one last year. You can do it without taking the duct off.

 

[y5359]

My mechanic was able to get mine to switch back to AC. He kept cycling the temp control at low speed and got it to switch. He thinks my temp actuator is going bad and needs to be replaced. Does anyone know the part number for it?

He said if I buy the part he would only charge me $80 for the install so I'm going to just let him replace it rather than mess with it myself.

 

[jerryb]

Does anyone know where or how the AC amplifier is grounded? After spending some time in the FSM it looks like most of my codes share the A46 plug ground at pin 18 at the AC amp. The FSM says A46 - 18 goes to a Body Ground but I can’t find info on where that is? Any ideas? I’ve ordered a EWD but have not got it yet. Maybe that will help me?

are you trying to chase a yellow green ground?