AHC suspension replacement (1 Viewer)

[AtinLango]

I have LC Amazon 2002 (Diesel). i have driven since 2018, and it is in very good condition. Have had no major issues other than maintenance.

Recently replaced "shocks absorbers" and all four globes since it was driving harshly. Since 2018, graduation test slowly reduced from around ten to around five as of the time of replacement recently. After replacement, the car is now driving so smoothly, but graduation test has remained at five, which is bothering me.

Any advice on whether I should worry about the graduations or not.

 

[AtinLango]

Start with simple.

1. Plug in all the sensors. Leave them all plugged in.
2. It is unlikely that you can open the sensors and assemble them again and fix anything. The sensor internals are very sensitive and the only reliable solution is new Toyota/Lexus sensors.
3. The car might be stuck in L because your torsion bars need adjustment. Crank each bar 5 turns up (clockwise). That should lower your pressures and make the car mroe likely to get to N.
4. You need to read data from the AHC computer. OBD Fusion with an ELM bluetooth OBD bluetooth dongle works. Or a laptop running techstream (available for download free on here). Once you connect you will quickly see what the problem is. Fixing this without reading that data is very, very time consuming and potentially expensive.

Front pressure sensor: 0.0 (individually, L and R each shows negatives)
Rear pressure: 5.9
Accumulator pressure sensor: 0.0

At first, the error codes were C1711, C1712, C1713. But after clearing, the error code changed to C1762 (abnormal oil pressure for pump).

After getting the readings above, we cranked the torsion bars clockwise five times, but it made no positive change. Now the car remains fully in L even if we remove the sensor switches.

I appreciate any help.

 

[suprarx7nut]

If you're still getting that error code, I bet there's air/gas in the line near the pump.

You might need to bleed more.

There's an active test in Techstream that forces the pump to run. You might need to use that to try bleeding more.

 

[AtinLango]

If you're still getting that error code, I bet there's air/gas in the line near the pump.

You might need to bleed more.

There's an active test in Techstream that forces the pump to run. You might need to use that to try bleeding more.

Thankyou. Can we bleed directly from the pump?

 

[suprarx7nut]

Thankyou. Can we bleed directly from the pump?

There's no bleed valve, but you can remove the line at the pump. It's tricky because if you open the line to bleed right at the pump, you still need significant bleeding once you reassemble the line.

 

[AtinLango]

There's no bleed valve, but you can remove the line at the pump. It's tricky because if you open the line to bleed right at the pump, you still need significant bleeding once you reassemble the line.

I have bought another 2.5 liter can of fluid in readiness for any bleeding.

 

[AtinLango]

I have bought another 2.5 liter can of fluid in readiness for any bleeding.

 

[AtinLango]

Meanwhile, I got a rude awakening from the mechanic who helped me to test using the diagnostic machine today. His immediate conclusion was that we should just replace the AHC pump. Well, I am not in a hurry because I understand the circumstances under which the problem has occurred (replaced shocks, globes, but did not flush initially since the original mechanic said it was not required; flushed later and found a lot of air; more air seemingly remaining in fluid; etc).

This particular mechanic (diagnostic) is not an official Toyota mechanic, but he reminded me of one statement I read online recently, and I quote:

"
Many toyota dealers have no idea about the ahc system, so ask around before you give it to somone throwing parts at it, on your cost, without beeing able to see where (and why) they are throwing parts. The fault codes (DTC) for the ahc are not to be trusted, so reading codes and changing parts accordingly becomes very expensive.
The ahc is a simple system, but with many parts.
"

I think I have to use my sense of judgment (plus those that I am getting from this forum) combined with the DTC.

My current inclination is that there is still air around locked around the pump that may be interfering with the pressures. Well, I may be wrong, but time will tell.

Will be updating as necessary.

 

[BullElk]

After bleeding system it is fairly easy to take pump apart to check possible fluid sludge and in reassemble confirming the pump is actual toast or not. I would say it is worth a try before replacing with new pump or new suspension.

 

[Wilsil]

Front pressure sensor: 0.0 (individually, L and R each shows negatives)
Rear pressure: 5.9
Accumulator pressure sensor: 0.0

At first, the error codes were C1711, C1712, C1713. But after clearing, the error code changed to C1762 (abnormal oil pressure for pump).

After getting the readings above, we cranked the torsion bars clockwise five times, but it made no positive change. Now the car remains fully in L even if we remove the sensor switches.

I appreciate any help.

How did you read those values?
You have to bring the system up from N to H before there is any readings.
It looks like you just plugged the laptop in and read off the numbers?

 

[AtinLango]

How did you read those values?
You have to bring the system up from N to H before there is any readings.
It looks like you just plugged the laptop in and read off the numbers?

I get your point. I actually realized later that those readings may be meaningless since the car is completely stuck in L.

How can i take readings in this state, or how can i force the car to move up?

 

[Wilsil]

Can you drop it to Low and move it to Normal?
Assuming you have fluid in the reservoir, sensors connected, all doors closed.

 

[AtinLango]

Can you drop it to Low and move it to Normal?
Assuming you have fluid in the reservoir, sensors connected, all doors closed.

The car is now completely stuck in L. It cannot move from there.

There is enough fluid, all sensors are connected. I close all doors whenever trying out.

 

[suprarx7nut]

Meanwhile, I got a rude awakening from the mechanic who helped me to test using the diagnostic machine today. His immediate conclusion was that we should just replace the AHC pump. Well, I am not in a hurry because I understand the circumstances under which the problem has occurred (replaced shocks, globes, but did not flush initially since the original mechanic said it was not required; flushed later and found a lot of air; more air seemingly remaining in fluid; etc).

This particular mechanic (diagnostic) is not an official Toyota mechanic, but he reminded me of one statement I read online recently, and I quote:

"
Many toyota dealers have no idea about the ahc system, so ask around before you give it to somone throwing parts at it, on your cost, without beeing able to see where (and why) they are throwing parts. The fault codes (DTC) for the ahc are not to be trusted, so reading codes and changing parts accordingly becomes very expensive.
The ahc is a simple system, but with many parts.
"

I think I have to use my sense of judgment (plus those that I am getting from this forum) combined with the DTC.

My current inclination is that there is still air around locked around the pump that may be interfering with the pressures. Well, I may be wrong, but time will tell.

Will be updating as necessary.

A bad pump is rare. Not impossible, but not common. The pump is very simple and very reliable.

Air in the pump is very common and commonly triggers your DTC.

I would not buy a new pump.

You can carefully disassemble the existing pump and check for sludge or gel, or you can continue bleeding (and maybe use the active test to force the pump to run).

 

[AtinLango]

A bad pump is rare. Not impossible, but not common. The pump is very simple and very reliable.

Air in the pump is very common and commonly triggers your DTC.

I would not buy a new pump.

You can carefully disassemble the existing pump and check for sludge or gel, or you can continue bleeding (and maybe use the active test to force the pump to run).

Thank you. Most appreciated.

 

[AtinLango]

The diagnostic mechanic came and promised to raise the car using Active test. He tried in vain. He insisted the pump was dead, and was asking for about 20 dollars for each test done. So far, i have grudgingly paid him about 60 dollars.

My first mechanic who originally changed the parts came after. He was quite confident he was going to resove the issue (and he did!!). He disassembled the pump. Cleaned quite a bit of sludge. A lot of air was inside too. Got rid of it too.

Tested pump direct on car battery.and it was ok.

Put new fluid in pump and installed it back in car. Immediately the car height started adjusting between L, N and H seamlessly like new. I guess it is sorted. The guy knows the pump inside out. But again he insisted that bleeding is not necessary. Well, i gave up.

Car driving like new again. Very comfortable. Comfort button working well too.

After pump was put back, i asked the diagnostic mechanic to check the pressures again. Never mind that means more money.

In Neutral, pressures are reading 0. Quite confusing. Of course the mechanics are not of much help regarding the machine readings. They dont know how to use the machine. Its just a gamble, but he wants his payment.

Graduation test isnt very promising. Seems still reading around 8. I want to drive a bit and do graduation test again.

In all these, it got most scary when i was told by the diagnostic mechanic to buy a new pump. I stood my ground and said NO because i understand the circumstances under which the problem started, and i am also well equipped with info from this forum.

I guess i need to relax a bit as i look to buying my own diagnostic machine so that i can test the pressures.

I owe it all to this wonderful forum.

 

[AtinLango]

The diagnostic mechanic came and promised to raise the car using Active test. He tried in vain. He insisted the pump was dead, and was asking for about 20 dollars for each test done. So far, i have grudgingly paid him about 60 dollars.

My first mechanic who originally changed the parts came after. He was quite confident he was going to resove the issue (and he did!!). He disassembled the pump. Cleaned quite a bit of sludge. A lot of air was inside too. Got rid of it too.

Tested pump direct on car battery.and it was ok.

Put new fluid in pump and installed it back in car. Immediately the car height started adjusting between L, N and H seamlessly like new. I guess it is sorted. The guy knows the pump inside out. But again he insisted that bleeding is not necessary. Well, i gave up.

Car driving like new again. Very comfortable. Comfort button working well too.

After pump was put back, i asked the diagnostic mechanic to check the pressures again. Never mind that means more money.

In Neutral, pressures are reading 0. Quite confusing. Of course the mechanics are not of much help regarding the machine readings. They dont know how to use the machine. Its just a gamble, but he wants his payment.

Graduation test isnt very promising. Seems still reading around 8. I want to drive a bit and do graduation test again.

In all these, it got most scary when i was told by the diagnostic mechanic to buy a new pump. I stood my ground and said NO because i understand the circumstances under which the problem started, and i am also well equipped with info from this forum.

I guess i need to relax a bit as i look to buying my own diagnostic machine so that i can test the pressures.

I owe it all to this wonderful forum.

Some pictures of the work.

 

[AtinLango]

Some bad news. Car is again stuck in L for the second time in as many weeks. Too irritating.

One thing is that the last time the mechanic removed and cleaned the pump, the system worked very well immediately. But he was not willing to bleed the system, and he did not do so. Yet, i fear there is still air inside.

Can one open the pump, clean it, put it back without bleeding afterwards? Is it not obvious that air would be trapped in, and likely cause more problems later?

Now i called him and he is saying we have to replace the pump. He is yet to come and check the system.

Question: is there any way i could try to bleed the system in its current stuck state? I would just get another mechanic to help me do so.

I appreciate your help.

 

[AtinLango]

Some bad news. Car is again stuck in L. Too irritating.

One thing is that the last time the mechanic removed and cleaned the pump, the system worked very well immediately. Bet he was not willing to bleed the system, and he did not do so. Yet, i fear there is still air inside.

Now i called him and he is saying we have to replace the pump. He is yet to come and check the system.

Question: is there any way i could try to bleed the system in its current stuck state? I would just get another mechanic to help me do so.

I appreciate your help.

For the record, for the last 5 years that i drove the car, it never had any single AHC issue. I religiously flushed the fluid on my own (with a mechanic helping) a few times without any issue whatsoever. It is only after the recent shock/globe changes that it started having this issue.

 

[Wilsil]

A reading of 0 pressure when in Neutral doesn't mean anything.
You have to move from N to H and wait tiit's settled, then read the pressure.

 

[AtinLango]

A reading of 0 pressure when in Neutral doesn't mean anything.
You have to move from N to H and wait tiit's settled, then read the pressure.

Oh, so the pressure is read when in H? I thought it is supposed to be read in N.