New King Springs - AHC issue - ECU reset?

[Clunky]

I installed new King Springs and now I'm getting pogo stick bounce with the rear, particularly noticeable at low speeds. In hunting through some AHC threads I came across this:

"Note that ‘rough ride’ can have several other causes – commonly, problematic or wrongly adjusted Height Control Sensors. Sensor problems may cause the AHC Electronic Control Unit (ECU) to put the system into ‘fail safe mode’ in which variable damping rates are prohibited and ride feels rough, particularly at low speeds."

I'm disconnecting the battery now in an attempt to reset the ECU to get out of fail safe mode.

Any other advice from AHC gurus?

I have new globes and pressures aren't too out of whack.

Also, does anyone have any advice for how to remove the AHC temperature sensor? Mine doesn't want to budge and I don't want to break anything by forcing it with tools.

 

[Clunky]

I adjusted the rear hight sensor a little higher and tried the AHC reset short process (Tc and E1 in dlc1), still bouncing

It doesn't bounce in high mode.

 

[Clunky]

@suprarx7nut any ideas?

 

[suprarx7nut]

Can you share a couple screenshots from Techstream? I'm curious to see readings at all three heights, starting in L.

 

[Clunky]

Can you share a couple screenshots from Techstream? I'm curious to see readings at all three heights, starting in L.

All taken with Temperature sensor still in...

Low:

Front Right: -50 mm
Front Left: -48.60 mm
Rear: -38 mm
Front Pressure: 0 Mpa-g
Rear Pressure: 0 Mpa-g
Accumulator Pressure 0 Mpa-g

Normal:

Front Right: -4.4 mm
Front Left: 0 mm
Rear: 2.20 mm
Front Pressure: 6.60 Mpa-g
Rear Pressure: 6.90 Mpa-g
Accumulator Pressure 10 Mpa-g

High:

Front Right: 35.40 mm
Front Left: 41.20 mm
Rear: 47.40 mm
Front Pressure: 9 Mpa-g
Rear Pressure: 3.2 Mpa-g
Accumulator Pressure 10 Mpa-g

 

[suprarx7nut]

All taken with Temperature sensor still in...

Low:

Front Right: -50 mm
Front Left: -48.60 mm
Rear: -38 mm
Front Pressure: 0 Mpa-g
Rear Pressure: 0 Mpa-g
Accumulator Pressure 0 Mpa-g

Normal:

Front Right: -4.4 mm
Front Left: 0 mm
Rear: 2.20 mm
Front Pressure: 6.60 Mpa-g
Rear Pressure: 6.90 Mpa-g
Accumulator Pressure 10 Mpa-g

High:

Front Right: 35.40 mm
Front Left: 41.20 mm
Rear: 47.40 mm
Front Pressure: 9 Mpa-g
Rear Pressure: 3.2 Mpa-g
Accumulator Pressure 10 Mpa-g

Any dtc active or stored? Should say at bottom right of Techstream AHC data list.

Do the damping levels (I forget what they're called) vary, centered around 8?

If you bounce the corners from the outside of the vehicle while running do they all behave the same?

 

[Clunky]

Any dtc active or stored? Should say at bottom right of Techstream AHC data list.

Do the damping levels (I forget what they're called) vary, centered around 8?

If you bounce the corners from the outside of the vehicle while running do they all behave the same?

No dtc

I'm using TYT II , not techstream, so I don't have access to damping levels.

The rear corners have the same bounce, the fronts don't seem to have any issues (and they are the same at both corners).

 

[suprarx7nut]

No dtc

I'm using TYT II , not techstream, so I don't have access to damping levels.

The rear corners have the same bounce, the fronts don't seem to have any issues (and they are the same at both corners).

Ok. Do front and rear bounce the same from the outside?

 

[OEMGUY0720]

May need to bleed rear ahc. That’ll be my first step. Symptom looks like AHC hydraulic fluid not moving/flowing as it’s supposed to. Static pressures are okay, movement isn’t.

 

[suprarx7nut]

May need to bleed rear ahc. That’ll be my first step. Symptom looks like AHC hydraulic fluid not moving/flowing as it’s supposed to. Static pressures are okay, movement isn’t.

Agreed. Recent globe replacement makes air in the lines a likely culprit.

 

[bentonrover]

You switched to heavier rear springs. Is there weight in the back? Like heavier bumper, tire carrier, draw system as such? It will definitely ride a little rough on stock setup.

 

[Beto Cruiser]

Point of reference, I put in King springs and have almost no weight in back (no 3rd row, armor, etc) and have no bounce. Hopefully air in the system after globe swap is the culprit. I still have my old globes, but all pressures in spec.

 

[suprarx7nut]

You switched to heavier rear springs. Is there weight in the back? Like heavier bumper, tire carrier, draw system as such? It will definitely ride a little rough on stock setup.

Point of reference, I put in King springs and have almost no weight in back (no 3rd row, armor, etc) and have no bounce. Hopefully air in the system after globe swap is the culprit. I still have my old globes, but all pressures in spec.

I also changed to King springs before I added most my weight goodies. Ride was barely different, IMO. Sounds like @Clunky is experiencing more than the spring characteristic change.

AHC is somewhat beneficial in this sense. Far as I can work out the physics of it, AHC will maintain a somewhat self-regulated spring rate for your given mechanical spring and load. If the mechanical spring gets swapped for something stronger, neutral pressures from AHC will drop and the effective spring rate of the AHC portion of the system drops. I believe that yields a net effective spring rate that's not necessarily much more than it was with the weaker springs. Maybe I'm over-simplifying the system's dynamics, but that's what makes sense to me.

This all said, the harsh bounce phenomenon tells me the damping is not working correctly. If there's not a DTC and pressures and sensor heights appear normal I think trapped air/gas in one or more of the actuator/shocks makes a lot of sense. A few rounds of flushing are a good idea.

 

[medtro]

Agreed. Recent globe replacement makes air in the lines a likely culprit.

No globe replacement recently. It was done many months ago.

 

[Hokie LX]

Whenever this has happened to me, it was caused by a bad rear sensor. Replaced the sensor and it went back to normal.

One thing to check…did you rear sensor mount get bent when you were changing springs? The rear slide mount that is used to adjust the rear sensor height can get bent if not detached before lowering the rear axle. This will cause the back to jack all the way up and ride harshly.

 

[Clunky]

Thanks for the ideas everyone. I'll check for air in the system and the rear sensor. The sensor mount is not bent.

 

[Clunky]

Whenever this has happened to me, it was caused by a bad rear sensor. Replaced the sensor and it went back to normal.

One thing to check…did you rear sensor mount get bent when you were changing springs? The rear slide mount that is used to adjust the rear sensor height can get bent if not detached before lowering the rear axle. This will cause the back to jack all the way up and ride harshly.

What part number did you use for rear sensor replacement?

 

[Hokie LX]

What part number did you use for rear sensor replacement?

The Toyota PN is: 89407-60010

I replaced all of my sensors years ago and RockAuto had the best price on the Aisin/OEM ones.

More Information for AISIN HST026

www.rockauto.com

I tried the cheap Dorman ones initially and they were trash. All failed within 3 months.

 

[suprarx7nut]

The Toyota PN is: 89407-60010

I replaced all of my sensors years ago and RockAuto had the best price on the Aisin/OEM ones.

More Information for AISIN HST026

www.rockauto.com

I tried the cheap Dorman ones initially and they were trash. All failed within 3 months.

That's been such a reliably bad experience I feel like we need a PSA stickied or something. The Dorman AHC sensors seem to be completely worthless.

 

[Hokie LX]

That's been such a reliably bad experience I feel like we need a PSA stickied or something. The Dorman AHC sensors seem to be completely worthless.

Agreed...one of the only times I have ventured away from OEM Toyota parts for a repair and it bit me. Immediately ordered the Aisin ones from RA and they've been going strong for 3-4 years now.