Is This the End for My AHC Pump? (1 Viewer)

Joined
Apr 18, 2020
Messages
27
Location
Little Rock, Arkansas
Good evening friendly AHC wizards,

I think it's time for a new AHC pump (motor) but I'm still finding my way around the system and wanted some confirmation before pulling the trigger. Here's the situation:

Background-My wife and I replaced all 4 AHC "shocks" with new OEM ones (and some other things, post to come once we are back to normal). Before this our AHC was completely functional with about 8 gradations of movement between high and low and good pressures (can provide specifics if helpful). I flushed the system about 8 months ago with no complications or concerns at the time or since.

Problem-now that we have everything hooked back up the truck is stuck in "neutral" even though its actually riding close to if not below what normally measures as low height. It won't cycle up or down.

When doing the short in the diagnostic port the motor runs and makes an *awful* screeching/grinding noise. It runs continuously, but it's only able to lift the vehicle up to something approximating neutral (the interior display always reads neutral) before it loses pressure and falls back down again.

Codes:
-C1761 AHC ECU Malfunction (this might be old. The off light has been blinking since we got it but not once has it affected functionality).
-C1762 Abnormal Oil Pressure for Pump

Data- front and rear pressures are reading 0.0, accumulator reading 0.3. This actually was the case before in neutral position sometimes, so I don't know how trustworthy these numbers are, but the pressure is definitely low (see next section).

Remedies attempted:
1) draining all 5 points- pressures were much lower than previously, even after running motor. No noticeable vehicle drop on draining.
2) manual operation of motor via short method- hoped maybe there was air trapped and this/bleeding the accumulator would fix/improve things. No such luck.


Thank you very much for all help in advance!
 
Joined
Dec 11, 2018
Messages
244
Location
EU
Air in system? - completely functional before, bad pressure and awful sound now points to this. The pump hates air and hates you after running on air.
 

suprarx7nut

The YotaMD Guy
Supporting Vendor
Joined
Sep 28, 2010
Messages
3,886
Location
Colorado
I would replace the pump. Relatively cheap and easy and it's a wear item at some point. Might as well knock it out!
 
Joined
Sep 24, 2018
Messages
496
Location
Central Virginia
So yours was the same situation and this fixed it?
Simmilar, I blead my system but botched it on the height accumulator when the house fell off and it ran dry letting air into the system. Took a lot of bleeding but eventually came around. As mentioned above the system is very sensitive to even a little air.
 
Joined
Dec 6, 2016
Messages
316
Location
Brisbane, Australia
Good evening friendly AHC wizards,

I think it's time for a new AHC pump (motor) but I'm still finding my way around the system and wanted some confirmation before pulling the trigger. Here's the situation:

Background-My wife and I replaced all 4 AHC "shocks" with new OEM ones (and some other things, post to come once we are back to normal). Before this our AHC was completely functional with about 8 gradations of movement between high and low and good pressures (can provide specifics if helpful). I flushed the system about 8 months ago with no complications or concerns at the time or since.

Problem-now that we have everything hooked back up the truck is stuck in "neutral" even though its actually riding close to if not below what normally measures as low height. It won't cycle up or down.

When doing the short in the diagnostic port the motor runs and makes an *awful* screeching/grinding noise. It runs continuously, but it's only able to lift the vehicle up to something approximating neutral (the interior display always reads neutral) before it loses pressure and falls back down again.

Codes:
-C1761 AHC ECU Malfunction (this might be old. The off light has been blinking since we got it but not once has it affected functionality).
-C1762 Abnormal Oil Pressure for Pump

Data- front and rear pressures are reading 0.0, accumulator reading 0.3. This actually was the case before in neutral position sometimes, so I don't know how trustworthy these numbers are, but the pressure is definitely low (see next section).

Remedies attempted:
1) draining all 5 points- pressures were much lower than previously, even after running motor. No noticeable vehicle drop on draining.
2) manual operation of motor via short method- hoped maybe there was air trapped and this/bleeding the accumulator would fix/improve things. No such luck.


Thank you very much for all help in advance!
I agree with the suggestions in earlier posts in this thread. In particular:

Clear all Diagnostic Trouble Codes (DTC’s) so that you know you are not dealing with old information. DTC’s will re-establish themselves if faults still exist.

Be aware that air in system can be hard to eliminate and may require multiple efforts. The thread leading up to Post #243 by @aharlan001 shows how frustrating this can be and the persistence which may be required:

AHC Inop after fluid change 2007 lx C1751 and C1762 - https://forum.ih8mud.com/threads/ahc-inop-after-fluid-change-2007-lx-c1751-and-c1762.1233088/page-13#post-13517321

When confident that air in the system is not a problem and if you are inclined to repair or replace the AHC Pump, then as mentioned by @BullElk it is not a big job.

To understand the AHC Pump, it is worth looking at the description and diagrams in

https://lc100e.github.io/manual/
Look for the index tabs starting at top left hand side of the opening page and choose these tabs in order to reach the General Description document:
New Car Features > CHASSIS > Suspension > Active Height Control Suspension.

Then suggest also review these well-illustrated posts:

Post #67 by @BullElk at AHC pump out? - https://forum.ih8mud.com/threads/ahc-pump-out.1226629/page-4#post-13401098 for pictures of a clogged pump.

Posts #69 and #70 by @IndroCruise at AHC pump out? - https://forum.ih8mud.com/threads/ahc-pump-out.1226629/page-4#post-13407297 and onwards shows pictures of AHC Pump disassembly and also show the tiny filters (strainers) within the Pump. Pump disassembly, cleanup of the pump and backwashing the filters (strainers) are all straightforward and is made easy by removing the motor/pump/tank assembly from the vehicle. Even if the decision is to replace the pump, disassembly of the existing pump is still recommended. It is better to know how much 'gloop' is in the system before installing a new pump and risking another blockage.

Toyota/Lexus and the various resellers do not offer internal pump parts for sale and instead offer the AHC pump unit in various combinations:

48910-60012 whole pump and motor assembly including pressure sensor, temperature sensor and AHC tank (Price example: USD1,204.04 on Partsouq)

48901-60010 pump only sub-assembly (Price example: USD160.79 on Partsouq)

Obviously repair/replacement of the AHC Pump involves first depressurising the system to allow the Pump to be removed. Reinstallation and reconnection requires repressurising the system, possibly using the “Active Test” to get the Pump running, and certainly involving the usual persistence and all-points bleed to clear air from the system.

The above notes assume that the AHC Pump motor is in good condition. It would make good sense to check the AHC Pump Motor by applying 12 volts to its power supply and briefly running to check no strange noises from bearings or brushes, or, remove end-cover from the motor and inspect. Probably it is OK -- pump motor problems are rarely reported. Some pics of the motor can be seen at Post #11 at AHC help ... yeah another one. - https://forum.ih8mud.com/threads/ahc-help-yeah-another-one.985078/#post-10980693.

Notes on pump removal and reinstallation can be found in the "Repair Manual" section of the FSM -- which was the source of the diagrams below:

AHC Pump and Motor Layout.jpg
 
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