2002 LX470 with Nav- Climate Control unresponsive

[RustyAF]

Hi all!
First post and first 100 series (2002 LX470). I recently have run into a problem where the Climate Control via the touchscreen is unresponsive. All buttons to the left side of the screen work completely fine, and the touchscreen is responsive to prompts that pop up after pressing buttons on the left side. All physical buttons on the top of the screen are unresponsive and do not light up when pressed, however when pressing the Climate button on the top left it takes me to the screen to choose air direction and fan strength but when pressing these buttons they stay highlighted for about a second and then return to their original state. I have read some different threads about this issue however I never received the "Check the connection of the air conditioner"

Symptoms are almost identical to this thread 2002 land cruiser- HVAC controls not responsive-SOLVED but AC fuse is not blown & AC compressor clutch trigger wire is not touching the serpentine belt.

Any pointers or help would be greatly appreciated because I'll be needing the defrosters for NJ weather very soon!

 

[excessive]

do you have any symptoms of water leaks, i.e. wet floorboards ?

 

[RustyAF]

I cleared the sunroof drains with weedwacker line when I bought the car, however during some heavy rain I did notice that the drivers side floorboard was a bit wet. I pulled the drivers side A pillar trim off and poured water from the upper corners of the windshield to replicate the problem. I saw a wet spot on the top part of the Drivers side A pillar trim and put some silicone sealant on the top left corner of the windshield from the inside, after that I've had no wet floorboards.

 

[w0lfgang]

I'm also having this issue despite not having any water incursions. The problem comes and goes, I had a pretty corroded negative battery terminal so I replaced it and that seemed to fix it for a while. Earlier this week the problem came back, so I pulled the fuse (not blown) and put a dab of WD-40 on it and it started working again. Turned the car off and the battery died and would not start without a jump. Car would not crank a second time after idling, so I took the battery to get load tested and they told me it was good.

The controls stopped working again today.

Update #1
I just removed the nav, stereo, & A/C amp assembly to attempt and check the circuit and test the A/C amp wire harness. I reassembled everything and now my controls work again. I would check your negative terminal connection, make sure it's clean and mounted well. After that unplug all of the wire harness at the A/C amp and maybe give each harness a little dielectric grease. Hope this helps!

Update #2 - 2/10/26
A/C is unresponsive again. No blown fuse, unplugging and plugging the A/C amp wire harness did not resolve anything. I have a new to me A/C amplifier on the way. From what I read in FSM, this should alleviate the problem. If not, I'm going to try and replace the Gateway ECU.

Update #3 - 2/18/26
After replacing the a/c amp, and gateway ecu I still had no luck with the controls. In the factory service manual there is a wiring diagram for the amp; the line supplying the am with power passes through the CIGAR fuse (see below). Replaced the fuse and now HVAC controls, as well as some spare parts.

 

[w0lfgang]

 

[w0lfgang]

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[w0lfgang]

This problem has come back yet again except this time it doesn't seem to be the fuse thats the issue. The other day I started it up and the A/C controls on screen were going crazy. The temperature was adjusting up and down then the air was switching between vents. This issue stopped and resolved itself shortly. About a week later I drove in the rain while the A/C was working fine, then I came back out to the car and the controls were unresponsive again. Since then my A/C kicked on randomly on the way home from breakfast w/ the wife. It has been unresponsive since then.

Leading up to this I noticed that the rear A/C wasn't blowing cold and the front started to blow less cold than normal. I know one of my schrader ports is leaking, there is oily residue along the high side.

I would like to add that I have checked volts and continuity at the relevant fuses and have inspected the wiring harness at the A/C amp and did not see anything out of the ordinary.

Question: Is there an issue similar to the PIN 60 problem that occurred on these years with this style of MFD?

Dumb Question: Could my controls be unresponsive due to the low pressure switch on the HVAC system?

 

[2001LC]

Sounds like water intrusion and or issue with aftermarket wiring. Although, can't rule out, a bad NAV unit or possibly a relay. Intermittent issue can be very hard to find. Since condition may not be present, as we test a circuit. These are very often associated with water entry. At first these issues, last until area dry. But over time, they can be persistent even once dry. Due to oxidation inhibit current flow (resistance). Grong fault connect at/to J/B box is one. The wire housing block to J/B, could be another. Also we see J/B fail, where back side has short.

Correcting ground cable at battery, reduce resistance from battery. This is a clue! But it could also have been coincidental of intermittence.

Is/Was anything else not working. Say like OAT reading out?

 

[w0lfgang]

Sounds like water intrusion and or issue with aftermarket wiring. Although, can't rule out, a bad NAV unit or possibly a relay. Intermittent issue can be very hard to find. Since condition may not be present, as we test a circuit. These are very often associated with water entry. At first these issues, last until area dry. But over time, they can be persistent even once dry. Due to oxidation inhibit current flow (resistance). Grong fault connect at/to J/B box is one. The wire housing block to J/B, could be another. Also we see J/B fail, where back side has short.

Correcting ground cable at battery, reduce resistance from battery. This is a clue! But it could also have been coincidental of intermittence.

Is/Was anything else not working. Say like OAT reading out?

Ok, I think I finally have this resolved for good. I followed a similar process to your other post and low and behold I've got a/c again. I actually took the entire JB out of the kick panel and removed all relays & fuses and gave them a good spray with contact cleaners and compressed air. Did the same thing to all the wiring harness as well. Also replaced all of fuses while I had it out.

There wasn't really any indication of water intrusion from what I could tell. All of the ports and pins seemed fairly clean. The only corrosion was around the circled harness connector which I think serves the overhead lights and sunroof.

Thanks for putting in your two cents. It's been a hot spring down here in Texas.

 

[2001LC]

You're more than welcome, for the 2 cents!