Help needed installing new AHC pump

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dwh13

dwh13

Joined
Nov 26, 2017
Threads
35
Messages
465
Location
Charleston, SC
Evening all, I’ve got a bad AHC pump (the one under the hood) and have been unable to find a clear write-up on how to replace it. It *sounds* easy enough, but I’m concerned on getting air into the system, and whether I’ll have to mess with shorting DLC1 circuits (I think that’s the term I’ve seen in my searches), as that’s out of my wheelhouse. Can anyone point me to a step by step guide, or write out the steps? I’d much rather buy a used pump from one of y’all to install myself than pay $700 for my shop to replace it. Cheers!
 
Sorry to hear that, especially after the Pleiades install! Wish I could help you but I have no clue on that one... Keep us posted on how it goes. Good luck!
 
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ChuckB said:
Sorry to hear that, especially after the Pleiades install! Wish I could help you but I have not clue on that one... Keep us posted on how it goes. Good luck!
Click to expand...
Yeah I’m just hoping that the spheres weren’t somehow the cause, and just exposed a weakness in the AHC system. My mechanic told me it wasn’t anything I did to cause the pump to fail, it just happened. Good man :p
 
Immediately after plugging in my Carsoft TYT, it refused to move from Lo to N, and has done so since. The pump runs constantly (and is throwing the DTC code saying that) and with a loud whining noise. I was already taking it to my local indy for an unrelated problem and had them check it out too - they recommended replacing the pump. My first question was whether the height sensor could be malfunctioning, making the pump run continuously to achieve the right height, but they said when they moved it up and down on the lift, they saw correct values populating for height on Techstream. FWIW, globes and fluid were changed a month ago.
 
Certainly possible you’ve got an internal blockage in the pump intake, there’s a TSB applicable to pre 03 systems on the issue. It was related to debris from the premature wearing of the height accumulator’s main seal.
Are they planning on fitting a takeoff replacement reservoir/pump/motor/pressure switch assembly or just replacing the actual gear pump? Either way it’s an invasive procedure that will require bleeding and possibly forcing the system to run via the active test.
 
PADDO said:
Certainly possible you’ve got an internal blockage in the pump intake, there’s a TSB applicable to pre 03 systems on the issue. It was related to debris from the premature wearing of the height accumulator’s main seal.
Are they planning on fitting a takeoff replacement reservoir/pump/motor/pressure switch assembly or just replacing the actual gear pump? Either way it’s an invasive procedure that will require bleeding and possibly forcing the system to run via the active test.
Click to expand...
I was going to just replace the entire assembly with a takeoff. I'm fine with bleeding since I've changed the fluid twice, but I'm not sure how to run the active test - I know it involves shorting some wires but I don't understand how to actually do it.
 
This is how you initiate the active test to force the pump to run.
1. Engine OFF, hood open and locate sockets Ts and E1 in the data link connector (DLC1) on the inner PS fender. Jump out Ts and E1 with a wire jumper or paper clip. Hint. There is a pin out diagram printed on the inside of DLC1’s connector cap to help locate Ts & E1.
2. Set damping control comfort switch to position 2, now start the vehicle and immediately push the DOWN rocker switch (as if to go to Low) 5 times in less then 5 seconds after starting. You should now be in test mode and the AHC OFF light should be rapidly flashing.
3. Turn the comfort switch to position 1 (softest damping) and now push and hold in the UP rocker switch (as if to raise to H) and after a delay of about 10 seconds the pump should kick in and, as you are holding the UP switch in, you should begin to raise at the front. Don’t hold the switch in too long and try and raise the front beyond its normal H height. Release the switch when satisfied that the pump has primed and is functioning.
4. Turn vehicle OFF, remove jumper from DLC1.
5. On restarting shut doors etc (or hold in door switch) for normal AHC operation and select N or L. Self leveling will sort itself out. Vehicle OFF and now you’re ready to bleed the system.
 
So in a bizarre twist of luck (for me at least), the message never got to the tech that I was going to replace the pump myself after they diagnosed the problem, so when I picked my truck up today, it had a new pump and a fluid flush for no charge! :bounce: I appreciate the info though - they assured me the Carsoft code reader didn't cause the pump to fail, but I'm trying to decide if I want to tempt luck again and pull it back out to try and get my neutral pressures...
 
I need to do this today or tomorrow. Just got a new used AHC pump assembly to replace my bad one (tested bad using the method @PADDO mentioned above). I’m stuck in LO with off flashing and all of that.

I am not having luck finding a step by step for this AHC pump r&r. Can anyone assist? If I had to guess:

1 Extract fluid from old pump assembly
2 remove pump assembly
3 install new pump assembly
4 top off fluid
5 bleed system

I should’ve checked this thread out a few days ago and ordered these seals. I’d rather not wait til Tuesday now for all these seals to ship in. How important do we think this is? The new used AHC pump assembly came with a 6 mo warranty which gives me confidence it’ll probably be fine, but I guess it’d be a major pain to do all of this again if I spring a leak. Also, I’d just as soon not pull the assembly apart at all since it was presumably done at the factory and I’m sure they do a better job than me.

Again, no idea what I’m doing. Anyone who can shed some light or let me know anything I’m missing, please let me know! Thanks!
 
Ugh, the pump I received is slightly different. This bit:

1996915


The part is labeled as being from a 2000 LX. I just had a shop move that piece over from my unit to the new one. Hopefully it works?

Starting to think the reason people rip out the AHC isn’t because the system is too complex, but due to a lack of support. Hopefully when I’m done I’ll be able to make a nice little write-up for the next guy.
 
Das Shtig said:
Starting to think the reason people rip out the AHC isn’t because the system is too complex, but due to a lack of support.
Click to expand...

I think that is the case in many situations. I don't claim to be an expert, but I'm trying to keep AHC alive!
 
Yeah, I’m onboard for becoming an expert! I fixed it, by the way, on Friday. Swapped that sensor from the old pump to the new, bolted it in and filled it up, bleed the lines, and started it up. Ran perfectly and has been working like new since! Great system, I’m hooked!!
 
Just in case it helps anyone else, I had to replace my pump again. Here are the steps - definitely a 1 :banana: at most:

Symptom: AHC stuck in low, OFF light flashing. DTCs of continuous current to pump motor (C1751) and abnormal oil pressure for pump (C1762).

First, decide what all you need to remove - you can take the entire assembly (bracket, pump, and reservoir) all at once, or you can just remove the pump and reservoir. I decided to take the latter route, because it looked like you'd have to pull the fender liner to get access to nuts holding the bracket to the body.

  1. Bleed the accumulator (long cylindrical bit on the DS outer frame rail)
  2. Use a siphon to remove as much fluid as possible from the reservoir
  3. Use a crowfoot 10 mm wrench to remove the fluid line from the pump and unclip the plastic clip holding the fluid line in place
  4. Remove the 3 electrical connectors
  5. Unbolt the pump from the black bracket - there are 3 10 mm bits - two nuts and a bolt. The nuts are on the front and back of the pump - you don't need to remove them completely, just loosen them halfway. The rear one can be a PITA to get to, but can be done with a standard wrench. A ratcheting wrench would help immensely.
  6. Unbolt the bolt - it's hidden as the head is underneath the pump but can be accessed by wrench
  7. Remove the pump and reservoir from the bracket - it lifts straight up.
  8. Swap in the new pump - I also swapped out my original reservoir with the replacement, as mine was cleaner inside. This can be done by removing the two bolts holding the reservoir to the pump.
  9. Reconnect the fluid hard line, then the bolts, nuts, and electrical connections.
  10. Refill with fluid well above the MAX line, start the car, and clear any codes if necessary. The pump should begin to run.
  11. Raise the vehicle to N so that your fluid level can be read accurately. Fill above MAX again.
  12. Turn vehicle off, flush fluid from the accumulator again to remove any air from the system.
  13. Turn the vehicle back on and let it adjust - add fluid to MAX as necessary.
All in all, including spending 30 minutes chasing down an issue that ended up being an improperly seated electrical connector, this job took me 1.5 hours and cost me $100 for the pump and fluid. I hope this helps someone in the future as I've never seen a complete DIY posted on how to replace the pump.
 
During this process do you close the cap for AHC reservoir? I mean when you’re bleeding and also at the end checking air in the system. Do you close the cap or leave it open?
 
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