LX470 AHC issues - pressure sensor 1998 Vs. 2002

Joined
Jan 18, 2012
Messages
76
Good morning all,

2002 LX470 CDN Spec 335000km. Rig is stuck in low, stiff as a board and has the flashing "off" . The system went from fully functional to dead over a period of a couple days, slowly going down to the Low position (or lower)

Vehicle was in for AC repairs at the local Toyota dealership and I asked them to look into some codes I pulled from the AHC system. 1718, 1732, 1763 are the 3 codes. I cannot get it into test mode to manually raise the vehicle.

Essentially they pulled the same codes I did and told me they needed to replace the $600 pressure sensor before anything else could be done.

After probing the sensor and testing per the FSM excerpts I found on some threads here myself, the voltage is out of range (5 volts from ground to one pin and .5 volts on ground to the other pin when pressing the raise button to neutral position. It is likely the sensor is in fact failed. The pump runs with 12 volts applied to it and the AHC Fuse is intact, Relay is functional. when the pump runs it sounds smooth for a few seconds then it sounds like it is dead heading which I would assume is due to the levelling valves being closed.

I have extensively read the AHC threads on the forum, some people say to unplug the pressure sensor and you should be able to raise the vehicle up if that is the problem. This does not work.

I found a complete used pump, pressure sensor, temp sensor and reservoir assembly a couple hours from where I live from a fellow that converted his rig to conventional suspension (1998 LX) purchased this and 3 the three level sensors for $200.00. Only problem is the pressure sensor is a "flat" connector 3 pin Vs the one only my '02 LX is the triangular one.

My first question: Are there any other things I can do to test out the system to get it out of fail-safe/lockout

Second : Can I use the 1998 pressure sensor if I use the old harness from the 98 truck and splice to the 3 wire harness on my truck. If so are the wire colors the same, if not does anyone have a pinout for the 2 sensors.



Thanks in advance


-Mitch
 

suprarx7nut

The YotaMD Guy
Supporting Vendor
Joined
Sep 28, 2010
Messages
4,473
Location
Colorado
Website
www.YotaMD.com
Good morning all,

2002 LX470 CDN Spec 335000km. Rig is stuck in low, stiff as a board and has the flashing "off" . The system went from fully functional to dead over a period of a couple days, slowly going down to the Low position (or lower)

Vehicle was in for AC repairs at the local Toyota dealership and I asked them to look into some codes I pulled from the AHC system. 1718, 1732, 1763 are the 3 codes. I cannot get it into test mode to manually raise the vehicle.

Essentially they pulled the same codes I did and told me they needed to replace the $600 pressure sensor before anything else could be done.

After probing the sensor and testing per the FSM excerpts I found on some threads here myself, the voltage is out of range (5 volts from ground to one pin and .5 volts on ground to the other pin when pressing the raise button to neutral position. It is likely the sensor is in fact failed. The pump runs with 12 volts applied to it and the AHC Fuse is intact, Relay is functional. when the pump runs it sounds smooth for a few seconds then it sounds like it is dead heading which I would assume is due to the levelling valves being closed.

I have extensively read the AHC threads on the forum, some people say to unplug the pressure sensor and you should be able to raise the vehicle up if that is the problem. This does not work.

I found a complete used pump, pressure sensor, temp sensor and reservoir assembly a couple hours from where I live from a fellow that converted his rig to conventional suspension (1998 LX) purchased this and 3 the three level sensors for $200.00. Only problem is the pressure sensor is a "flat" connector 3 pin Vs the one only my '02 LX is the triangular one.

My first question: Are there any other things I can do to test out the system to get it out of fail-safe/lockout

Second : Can I use the 1998 pressure sensor if I use the old harness from the 98 truck and splice to the 3 wire harness on my truck. If so are the wire colors the same, if not does anyone have a pinout for the 2 sensors.



Thanks in advance


-Mitch

Pressure sensor appears to be <$250 from Partsouq if you want a new one.


I would start your work at the ECU. Wiring harness faults are more likely than component failures, IMO. If you have a DMM and skinny probes, you can measure the pins and see if the ECU sees the same component resistance as the component itself. If not, the harness is probably your fault. I like starting with this because it can avoid a lot of parts swapping work. Taking the trim off is a little annoying, but much better than electrical connector surgery.
 
Joined
Jan 18, 2012
Messages
76
Pressure sensor appears to be <$250 from Partsouq if you want a new one.


I would start your work at the ECU. Wiring harness faults are more likely than component failures, IMO. If you have a DMM and skinny probes, you can measure the pins and see if the ECU sees the same component resistance as the component itself. If not, the harness is probably your fault. I like starting with this because it can avoid a lot of parts swapping work. Taking the trim off is a little annoying, but much better than electrical connector surgery.
Nice find on the pressure sensor. I have always been hesitant to purchase parts from overseas and from sites I am not familiar with however would be happy to with a referral like this.

I will buy a new one if I can confirm the sensor is shot, just didn't want to spend big bucks throwing parts at it. Are you aware of if the 98 and 02 sensors are the same in terms of electrical values?
 

suprarx7nut

The YotaMD Guy
Supporting Vendor
Joined
Sep 28, 2010
Messages
4,473
Location
Colorado
Website
www.YotaMD.com
Nice find on the pressure sensor. I have always been hesitant to purchase parts from overseas and from sites I am not familiar with however would be happy to with a referral like this.

I will buy a new one if I can confirm the sensor is shot, just didn't want to spend big bucks throwing parts at it. Are you aware of if the 98 and 02 sensors are the same in terms of electrical values?

Partsouq is pretty well loved here. Legit parts from a mega-seller that supplies the globe. They often ship faster than domestic dealers.

Sensor electrical values. Let me go check my manuals. I have an electrical wiring manual from an 06 and 99 and can compare the two.
 

suprarx7nut

The YotaMD Guy
Supporting Vendor
Joined
Sep 28, 2010
Messages
4,473
Location
Colorado
Website
www.YotaMD.com
Alright, so in these more recent manuals the electrical values aren't all published in the wiring manual (most values were published in the early 90's ones). Anyways, here's the connector comparison. The wiring diagrams of the pressure circuits look identical between the 98 and 06. 06 has the triangle. 98 has the flat connector. Both F1 and both pinouts used for the same conductors.

For the 06, here's what the manual says:
Approx 5V at pin 1 of the pressure sensor to ground (pin 3).
1.48 to 1.85V signal from the pressure sensor (pins 2 and 3).

I assume you should get those ballpark values across all years for the 100, but don't have the FSM for anything but the 06 to verify.

p-Icsk4BMKJk-m3oeKK5SsBZKI88_g74pbaBsgaJMdEcA8Dwh9r3IISOJ9NVVYJK_kedAjd8GJvuvXVY8L5qOrpolOEaASrAAWGgFIQHDi3YAwDSi24kIDOZuv2Qr4DlouA5qk1vj3Y4S4FEBH_5fvF-_LMEw-s0WBHXUanjMY1GkXjX4pmQRasz7ELFWY3KdahX2dwXlIma4CvG4eMPXFNGpTG3NCGZSgK-tTRzpfwyP8XwGXrtgvRD0NQNjGr9g6PUTMHRskWWXWqtvuqvBmvbb3Zid6QAxuaLlztmhAjopXSsIGQ7QuSqsBEwjw_Yw7gbg1SQSjzKY4waMZ8x7VODFkGXJ-BPhAd3oYJVbjgnJFrB4yB-fEeLT0O2YZQmoDvT6PsgpBQ4VpPBtcMkd_5lux1F4hsM4oVWcpubj5PAzj1SNmlcRpSRSV4rch_6eB2tuE3HVBiZxbf28FgyNxqUuD02qFuJpuKzHcSVn9-EYRkuwGySVeiyLK-bvnezcm0lPpT3UWeXAN-z26qR-i5rxSzgimfNhmpPMWmQsHfyRkDCCXEetRCdbvwMpQUXUHvDbcUiQ3FY5zjHbntyLlxvyxEefd-3cBJiecpXidc51_HtbzZpMqSbcgwO0ndFsKvFVInW66bQ_gb2hFrIfN2s5BdDJBf_jm33WhBGdLQH2hYO7dX20Phm7GCGpiXf7NXjGNtkLPnVBfhhz9OdcwrhOA=w703-h937-no
 
Joined
Jan 18, 2012
Messages
76
Damn you're good.

I was getting .5v on the pin 2 and 3 when running without the jumper installed on the diagnostics plug with or without pressing the raise button...

Im going to try changing the sensor with the users 98 sensor and make a quick harness adapter for it for testing...


Any idea how difficult it will be to bleed the air out when I change the sensor? will I be able to just crack the flare nut on the discharge of the pump?

-M
 

suprarx7nut

The YotaMD Guy
Supporting Vendor
Joined
Sep 28, 2010
Messages
4,473
Location
Colorado
Website
www.YotaMD.com
Damn you're good.

I was getting .5v on the pin 2 and 3 when running without the jumper installed on the diagnostics plug with or without pressing the raise button...

Im going to try changing the sensor with the users 98 sensor and make a quick harness adapter for it for testing...


Any idea how difficult it will be to bleed the air out when I change the sensor? will I be able to just crack the flare nut on the discharge of the pump?

-M
No idea honestly. I've never had an issue with air in any part of the system, but plenty have. Bleeding *should* be simple, albeit tedious. There are multiple ways to run the pump during the bleed process to make it go quickly. Most folks just cycle the system over and over and over.
Last question,

how does one clear the codes from the AHC ECU?
I've always cleared via Techstream. I think there's a way to manually do it with jumpers and or pulling fuses. I don't have the fsm for the early year LX, so can't look up the manual process, sorry!
 
Joined
Jan 18, 2012
Messages
76
I replaced the sensor with the 98 one. hooked it up per the pinout and the AHC lights would not illuminate at all. I reversed pin 1 and 3 as those are the only one that could be screwed up and I had the same problem as before.

There is no way to get the pump to run when it is in fail safe mode.

Anyone out there know how to clear the codes on the 02 lx AHC computer?
 
Joined
Jan 18, 2012
Messages
76
Can you link a reputable source for the cable and software? is the software free and you just need to pay for the cable or is it a kit?


I just ordered a new sensor from Partsouq hope to see it within a couple weeks. $320 bucks with shipping in our worthless CAD.


Techstream. If you're gonna mess with AHC, get it.
 

suprarx7nut

The YotaMD Guy
Supporting Vendor
Joined
Sep 28, 2010
Messages
4,473
Location
Colorado
Website
www.YotaMD.com
Can you link a reputable source for the cable and software? is the software free and you just need to pay for the cable or is it a kit?


I just ordered a new sensor from Partsouq hope to see it within a couple weeks. $320 bucks with shipping in our worthless CAD.
So here's the deal with Techstream.

The "reputable source" is Toyota and the software and hardware is $1600 for one year. $1300 each year after that to keep the license active. See below.

OR if you're not a professional shop:

Any number of ebay/amazon offers where the cable is $30-$100 and the software is included or available via many sources in the enthusiast community.


There's a massive gap in this market because Toyota never meant for you (a normal car owner that doesn't own a full garage shop) to purchase Techstream. Toyota then completely failed their customers when they failed to properly train and equip technicians for the most basic AHC upkeep success thereby making authorized dealers a non-viable option for AHC.

1638162996837.png
 

Users who are viewing this thread

Top Bottom