AHC Replacement (1 Viewer)

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Joined
Jan 14, 2004
Threads
30
Messages
137
Hi, I have recently had my AHC replaced with standard suspension. The 'H' light, on the cluster is lit up and the 'OFF' light is constantly flashing. Does anyone know if there are fuses which I need to remove? Thanks, all.
 
You need to unplug the three plugs to the AHC computer under your steering column and remove the AHC fuse under the hood.
 
You need to unplug the three plugs to the AHC computer under your steering column and remove the AHC fuse under the hood.
Thanks, Josh. Not being mechanically minded, how would I know which plugs to detach. Are they marked? Thanks, Josh
 
If you use the "Search" on this forum, there is a thread with pictures I believe.
 
Hi, I have recently had my AHC replaced with standard suspension. The 'H' light, on the cluster is lit up and the 'OFF' light is constantly flashing. Does anyone know if there are fuses which I need to remove? Thanks, all.

The location of the Suspension Control ECU on a Right Hand Drive vehicle is shown on the diagram below -- it is a bit of struggle to reach it and pull the three plugs but it can be done.

The role of each of the terminals is explained in the attachment -- these all can be disconnected (by pulling the three plugs) when AHC/TEMS is removed and replaced with a conventional suspension.

You could remove completely the ECU and the attached AHC Main Relay -- but suggest leave them in place, test drive after pulling plugs, just to be sure that there are no ''side effects' -- none are expected.

AHC - RHD ECU and Main Relay Location.jpg
 

Attachments

  • AHC - Terminals of ECU.pdf
    58.4 KB · Views: 50
The location of the Suspension Control ECU on a Right Hand Drive vehicle is shown on the diagram below -- it is a bit of struggle to reach it and pull the three plugs but it can be done.

The role of each of the terminals is explained in the attachment -- these all can be disconnected (by pulling the three plugs) when AHC/TEMS is removed and replaced with a conventional suspension.

You could remove completely the ECU and the attached AHC Main Relay -- but suggest leave them in place, test drive after pulling plugs, just to be sure that there are no ''side effects' -- none are expected.

View attachment 3011769
Really helpful! Thank you so much!
 
The location of the Suspension Control ECU on a Right Hand Drive vehicle is shown on the diagram below -- it is a bit of struggle to reach it and pull the three plugs but it can be done.

The role of each of the terminals is explained in the attachment -- these all can be disconnected (by pulling the three plugs) when AHC/TEMS is removed and replaced with a conventional suspension.

You could remove completely the ECU and the attached AHC Main Relay -- but suggest leave them in place, test drive after pulling plugs, just to be sure that there are no ''side effects' -- none are expected.

View attachment 3011769
Hi, again, Indocruise. If I could impose on your knowledge, one more time, please. Re the plugs etc., to be removed. I came across instructions on the site where I bought the Pedders kit from. They included instructions on removal of plugs, etc. The instructions seem to place the plugs just under the reservoir, which would be really convenient. I looked under it and there does seem to be three plugs there. I'm enclosing attachments of their instructions. Could this be correct?

Screenshot_2022-05-20-08-26-00-991_com.adobe.reader.jpg


Screenshot_2022-05-20-08-26-26-971_com.adobe.reader.jpg
 
Hi, again, Indocruise. If I could impose on your knowledge, one more time, please. Re the plugs etc., to be removed. I came across instructions on the site where I bought the Pedders kit from. They included instructions on removal of plugs, etc. The instructions seem to place the plugs just under the reservoir, which would be really convenient. I looked under it and there does seem to be three plugs there. I'm enclosing attachments of their instructions. Could this be correct?

View attachment 3013641

View attachment 3013642

The reply from @JOSHD at Post #2 and my Post #6 in this thread aims to disconnect completely the Suspension Control ECU (sometimes called the AHC ECU or the AHC computer). This is located in your Right Hand Drive vehicle as depicted in Post #6, high up under the dashboard, above and to the left of your left foot.

You can see what this ECU looks like at the link below (this is the 2006 RHD version, might be slightly different on your model year, 1998?) but in any case, even in 1998, it will have the same receptacles which receive three plugs from the main wiring harness under the dash:
Toyota 89290-60031 (8929060031) COMPUTER, SUSPENSION CONTROL - https://www.amayama.com/en/part/toyota/8929060031

For AHC/TEMS removal purposes, the idea in these earlier Posts is to disconnect completely and de-power the AHC ECU by pulling all three three plugs from the receptacles in the ECU, and also pulling the 50 Amp AHC fuse in the Junction Box in the engine bay. The aim is to allow removal of the AHC ECU and its attached AHC Main Relay, and also allow removal of the complete AHC Pump & Motor Unit from the engine bay, after removing all three electrical connections at the AHC Pump & Motor Unit and the hydraulic connection.

The alternative in your Post #8 above appears to involve leaving in place the complete AHC Pump & Motor Unit in the engine bay and disconnecting two of the three connectors to this unit – see illustrated attachment below to see which connectors are being described. This method appears to involve leaving the connection to the Pressure Sensor in place, even though there is no pressure to measure. Removal of the AHC Relay and the AHC 50 Amp fuse also is described.

Presumably this alternative works – but I cannot attest to that because I have never tried it. Without studying the Electrical Wiring Diagram (EWD) for your model year, I am not sure why the connection to the Pressure Sensor is left in place – presumably it means that there still is an electrical feed going to the AHC indicator lights.

Whatever, there is no downside to trying the alternative described in your Post #8. It will either work as desired, or not. There is no downside. No damage will be caused.

Hope this helps! This is some irony in this thread for me – mostly I advise on how to keep the excellent AHC/TEMS systems on LC100 and LX470 alive and working as designed – but it appears that your circumstances are beyond that point ….
 

Attachments

  • AHC Pump and Sensor Connections.pdf
    180.4 KB · Views: 37
You have been so helpful! Really appreciate it. Thank you!
 

Users who are viewing this thread

Back
Top Bottom