AHC Please for the love of god. (1 Viewer)

[lx470camperman]

Hello all my peoples. I have a 97 lx470. AHC off is flashing. It wont move and ride is stiff. I do not have a computer that i can download tech stream to and cant afford one. Looking to see if there is anyone in the area that can help a brother out. I'm not savvy with electronics but am more than willing to throw someone a few bucks to help me out. Thanks in advance.

 

[Escape Artist]

Hey buddy, what part of the world are you in? This something that just started? How long have you had the car? Couple of things you can do ... check that the fluid level is correct between the low and high marks in the tank. Will the car move into high mode? Or is it stuck in "low" ... if you can get it to go into high or low modes (Door have to be closed, engine running) than you wanna look to see how many "graduation" marks on that reservoir bottle the fluid covers. If you drop the truck from high all the way to low and count the little tick marks, 14 would be like new, 7 marks would be the lower limit of passing really. 6 And you likely need new globes. You can find them much cheaper than the dealership, just make sure they are OEM. Looking at maybe 200 bucks a pop or a little more.

You can flush the fluid, drain each accumulator etc ... please read up and watch some YouTube on how to do this. There is a great thread here The ABCs of AHC - How to Measure, Flush, and Adjust all in one place - https://forum.ih8mud.com/threads/the-abcs-of-ahc-how-to-measure-flush-and-adjust-all-in-one-place.1211999/

You may have the pressures out of spec ... you will need some kind of code reader (Even the OBDMX+ will work) to check the pressures. They should be 6.9 in front and about 6 in the rear give or take 0.5 Mpa. But I would imagine it is your globes ... they do wear out eventually. Did you peak underneath the truck? Any signs of hydraulic fluid leaks? There is a manifold I think under the passenger side, inside of the frame rail ... square box with maybe four or so hydraulic lines coming out of it. There is an accumulator pump etc ... does it make any noise ever?

There, if I remember correctly, are a few fuses/relays that you can check as well. I think I paid like 50 bucks for this Bluetooth scanner OBDLink MX+ from Amazon. Will get the job done for ya and is able to access the AHC computer, check pressures and read codes. I also have TechStream ... see "How to tech stream in five minutes" on this forum ... it is more fickle but also can be used. *REMEMBER that there is a temperature sensor closest to the firewall on the pump assembly beneath the reservoir on the passenger side of the engine compartment, it has two wires. My field service manual says to disconnect that one when checking the rear pressure. The Center connector with 3 wires is the pressure sensor. Forward of that with two heavier wires is the pump motor power. Check the connection of all of these.

What year is your car? Give us more info ... you just get it and it is doing this?

 

[lx470camperman]

Hey buddy, what part of the world are you in? This something that just started? How long have you had the car? Couple of things you can do ... check that the fluid level is correct between the low and high marks in the tank. Will the car move into high mode? Or is it stuck in "low" ... if you can get it to go into high or low modes (Door have to be closed, engine running) than you wanna look to see how many "graduation" marks on that reservoir bottle the fluid covers. If you drop the truck from high all the way to low and count the little tick marks, 14 would be like new, 7 marks would be the lower limit of passing really. 6 And you likely need new globes. You can find them much cheaper than the dealership, just make sure they are OEM. Looking at maybe 200 bucks a pop or a little more.

You can flush the fluid, drain each accumulator etc ... please read up and watch some YouTube on how to do this. There is a great thread here The ABCs of AHC - How to Measure, Flush, and Adjust all in one place - https://forum.ih8mud.com/threads/the-abcs-of-ahc-how-to-measure-flush-and-adjust-all-in-one-place.1211999/

You may have the pressures out of spec ... you will need some kind of code reader (Even the OBDMX+ will work) to check the pressures. They should be 6.9 in front and about 6 in the rear give or take 0.5 Mpa. But I would imagine it is your globes ... they do wear out eventually. Did you peak underneath the truck? Any signs of hydraulic fluid leaks? There is a manifold I think under the passenger side, inside of the frame rail ... square box with maybe four or so hydraulic lines coming out of it. There is an accumulator pump etc ... does it make any noise ever?

There, if I remember correctly, are a few fuses/relays that you can check as well. I think I paid like 50 bucks for this Bluetooth scanner OBDLink MX+ from Amazon. Will get the job done for ya and is able to access the AHC computer, check pressures and read codes. I also have TechStream ... see "How to tech stream in five minutes" on this forum ... it is more fickle but also can be used. *REMEMBER that there is a temperature sensor closest to the firewall on the pump assembly beneath the reservoir on the passenger side of the engine compartment, it has two wires. My field service manual says to disconnect that one when checking the rear pressure. The Center connector with 3 wires is the pressure sensor. Forward of that with two heavier wires is the pump motor power. Check the connection of all of these.

What year is your car? Give us more info ... you just get it and it is doing this?

Thank. I have peaked underneath my truck. I had a sensor link in the front break and i replaced it and now nothing works. no codes are being thrown on my obxll. the light is flashing. it is stuck in N but says it is in low. No noises from the pump. All fuses are in proper working order. I will read your thread. Looking for an old laptop on fb marketplace right now. ordered a cable for tech stream. will look into a different scanner. What type do you have. Also when it happen i adjusted it to high at an intersection then went around a corner now nothing. Electronics are silly and maddening. Thanks in advance.

 

[uHu]

Re TechStream: I got my old laptop from a primary school that was throwing away 10-20 years old laptops, with Win XP. Perfect - even managed to get a working battery for it.
Re front sensor link: If the AHC ECU get signals saying that the two front sensors are at very different heights, it will just turn off the AHC system. You really need TechStream, but it is possible to measure voltages on the sensors (or resistance if they are disconnected), to find out approximately which height they report to the ECU.

 

[lx470camperman]

Re TechStream: I got my old laptop from a primary school that was throwing away 10-20 years old laptops, with Win XP. Perfect - even managed to get a working battery for it.
Re front sensor link: If the AHC ECU get signals saying that the two front sensors are at very different heights, it will just turn off the AHC system. You really need TechStream, but it is possible to measure voltages on the sensors (or resistance if they are disconnected), to find out approximately which height they report to the ECU.

Silly question but how would you measure volts. I have a volt meter
Thanks in advance

 

[suprarx7nut]

Silly question but how would you measure volts. I have a volt meter
Thanks in advance

You'll be looking for Volts - DC.



It's worth learning how to use the multimeter for lots of things in life. The world isn't getting any less "electric" and this is a fundamental tool of most any electrical project. Enjoy!

 

[Escape Artist]

Just to chime back in … these guys are right about the sensor. Make sure you’re using Toyota OEM sensor parts. There’s a couple threads on here where people of used aftermarket sensors and couldn’t quite get the system to work.

 

[uHu]

Read the FSM. Lotsa tips, also for voltmeter readings.

 

[lx470camperman]

Hey buddy, what part of the world are you in? This something that just started? How long have you had the car? Couple of things you can do ... check that the fluid level is correct between the low and high marks in the tank. Will the car move into high mode? Or is it stuck in "low" ... if you can get it to go into high or low modes (Door have to be closed, engine running) than you wanna look to see how many "graduation" marks on that reservoir bottle the fluid covers. If you drop the truck from high all the way to low and count the little tick marks, 14 would be like new, 7 marks would be the lower limit of passing really. 6 And you likely need new globes. You can find them much cheaper than the dealership, just make sure they are OEM. Looking at maybe 200 bucks a pop or a little more.

You can flush the fluid, drain each accumulator etc ... please read up and watch some YouTube on how to do this. There is a great thread here The ABCs of AHC - How to Measure, Flush, and Adjust all in one place - https://forum.ih8mud.com/threads/the-abcs-of-ahc-how-to-measure-flush-and-adjust-all-in-one-place.1211999/

You may have the pressures out of spec ... you will need some kind of code reader (Even the OBDMX+ will work) to check the pressures. They should be 6.9 in front and about 6 in the rear give or take 0.5 Mpa. But I would imagine it is your globes ... they do wear out eventually. Did you peak underneath the truck? Any signs of hydraulic fluid leaks? There is a manifold I think under the passenger side, inside of the frame rail ... square box with maybe four or so hydraulic lines coming out of it. There is an accumulator pump etc ... does it make any noise ever?

There, if I remember correctly, are a few fuses/relays that you can check as well. I think I paid like 50 bucks for this Bluetooth scanner OBDLink MX+ from Amazon. Will get the job done for ya and is able to access the AHC computer, check pressures and read codes. I also have TechStream ... see "How to tech stream in five minutes" on this forum ... it is more fickle but also can be used. *REMEMBER that there is a temperature sensor closest to the firewall on the pump assembly beneath the reservoir on the passenger side of the engine compartment, it has two wires. My field service manual says to disconnect that one when checking the rear pressure. The Center connector with 3 wires is the pressure sensor. Forward of that with two heavier wires is the pump motor power. Check the connection of all of these.

What year is your car? Give us more info ... you just get it and it is doing this?

Also in michigan. Have been looking for a solid cruiser tech around me as well. Need a timing belt done and cant do it myself. Its beyond me but have all the parts.

 

[lx470camperman]

Thank. I have peaked underneath my truck. I had a sensor link in the front break and i replaced it and now nothing works. no codes are being thrown on my obxll. the light is flashing. it is stuck in N but says it is in low. No noises from the pump. All fuses are in proper working order. I will read your thread. Looking for an old laptop on fb marketplace right now. ordered a cable for tech stream. will look into a different scanner. What type do you have. Also when it happen i adjusted it to high at an intersection then went around a corner now nothing. Electronics are silly and maddening. Thanks in advance.

ok so

Hey buddy, what part of the world are you in? This something that just started? How long have you had the car? Couple of things you can do ... check that the fluid level is correct between the low and high marks in the tank. Will the car move into high mode? Or is it stuck in "low" ... if you can get it to go into high or low modes (Door have to be closed, engine running) than you wanna look to see how many "graduation" marks on that reservoir bottle the fluid covers. If you drop the truck from high all the way to low and count the little tick marks, 14 would be like new, 7 marks would be the lower limit of passing really. 6 And you likely need new globes. You can find them much cheaper than the dealership, just make sure they are OEM. Looking at maybe 200 bucks a pop or a little more.

You can flush the fluid, drain each accumulator etc ... please read up and watch some YouTube on how to do this. There is a great thread here The ABCs of AHC - How to Measure, Flush, and Adjust all in one place - https://forum.ih8mud.com/threads/the-abcs-of-ahc-how-to-measure-flush-and-adjust-all-in-one-place.1211999/

You may have the pressures out of spec ... you will need some kind of code reader (Even the OBDMX+ will work) to check the pressures. They should be 6.9 in front and about 6 in the rear give or take 0.5 Mpa. But I would imagine it is your globes ... they do wear out eventually. Did you peak underneath the truck? Any signs of hydraulic fluid leaks? There is a manifold I think under the passenger side, inside of the frame rail ... square box with maybe four or so hydraulic lines coming out of it. There is an accumulator pump etc ... does it make any noise ever?

There, if I remember correctly, are a few fuses/relays that you can check as well. I think I paid like 50 bucks for this Bluetooth scanner OBDLink MX+ from Amazon. Will get the job done for ya and is able to access the AHC computer, check pressures and read codes. I also have TechStream ... see "How to tech stream in five minutes" on this forum ... it is more fickle but also can be used. *REMEMBER that there is a temperature sensor closest to the firewall on the pump assembly beneath the reservoir on the passenger side of the engine compartment, it has two wires. My field service manual says to disconnect that one when checking the rear pressure. The Center connector with 3 wires is the pressure sensor. Forward of that with two heavier wires is the pump motor power. Check the connection of all of these.

What year is your car? Give us more info ... you just get it and it is doing this?

ok so I have learned that upon turning my car into the on position my vehicle self levels but the off light is still blinking and it says it is in low but is in neutral. so the pump works and the car levels but the ahce is just not working. I will check the switches next but I believe I already checked them. Scanned as well with an OBX2 with no luck. Not seeing any codes.

 

[usedname]

You sure you have enough fluid in the reservoir? Mine did that once when fluid was low.

 

[jLB]

Hello all my peoples. I have a 97 lx470. AHC off is flashing. It wont move and ride is stiff. I do not have a computer that i can download tech stream to and cant afford one. Looking to see if there is anyone in the area that can help a brother out. I'm not savvy with electronics but am more than willing to throw someone a few bucks to help me out. Thanks in advance.

I assume that the “97” is a typo?

 

[lx470camperman]

I assume that the “97” is a ty

Read the FSM. Lotsa tips, also for voltmeter readings.

what is th FSM

 

[uHu]

Search results for query: fsm download - https://forum.ih8mud.com/search/7381831/?q=fsm+download&t=post&c[child_nodes]=1&c[nodes][0]=26&o=date

 

[jLB]

what is th FSM

Factory Service Manual.

 

[Escape Artist]

I got ten bucks that says it's a sensor. Aftermarket sensor, I'm guessing, maybe was installed at some point and the ECU is very fickle about any voltage drop. Cheap fix ... replace with OEM. Thirty minute job ... YouTube it. Don't even have to remove the tire. Two in the front, one in the back. Buy one, plug it in and see, no fix, return it and get the other one and try again ... etc.

 

[lx470camperman]

ok so i finally figured out tech stream. I am currently throwing the following ahc codes.
c1736 accumulator solinoid circuit
c1762 abnormal oil pressure for pump
and
c1764 pressure abnormality by not opening accumulator valve.
Any thoughts my intelligent folks?????

 

[suprarx7nut]

ok so i finally figured out tech stream. I am currently throwing the following ahc codes.
c1736 accumulator solinoid circuit
c1762 abnormal oil pressure for pump
and
c1764 pressure abnormality by not opening accumulator valve.
Any thoughts my intelligent folks?????

Wire harness fault is my guess. 1736 will cause the 1762 code as well. Perhaps the 1764 too.

Likely along the length of wire from the B1 connector in the driver rear corner of the car up to the Height Accumulator midway along the frame. The wire is mostly hidden so you cannot just do a simple visual inspection (unless you get real lucky and it's damaged where you can see it). Generally, you have to use a DMM to test each circuit at that B1 connector and follow the faulty circuit.

Easy problem to detect if you have a wiring diagram and know how to use it. Quite difficult if you don't.

 

[lx470camperman]

Wire harness fault is my guess. 1736 will cause the 1762 code as well. Perhaps the 1764 too.

Likely along the length of wire from the B1 connector in the driver rear corner of the car up to the Height Accumulator midway along the frame. The wire is mostly hidden so you cannot just do a simple visual inspection (unless you get real lucky and it's damaged where you can see it). Generally, you have to use a DMM to test each circuit at that B1 connector and follow the faulty circuit.

Easy problem to detect if you have a wiring diagram and know how to use it. Quite difficult if you don't.

Thank for the response it will be my lead investigation this afternoon. lol whats a DMM

 

[lx470camperman]

Wire harness fault is my guess. 1736 will cause the 1762 code as well. Perhaps the 1764 too.

Likely along the length of wire from the B1 connector in the driver rear corner of the car up to the Height Accumulator midway along the frame. The wire is mostly hidden so you cannot just do a simple visual inspection (unless you get real lucky and it's damaged where you can see it). Generally, you have to use a DMM to test each circuit at that B1 connector and follow the faulty circuit.

Easy problem to detect if you have a wiring diagram and know how to use it. Quite difficult if you don't.

digital multimeter haha check i got one