danthemanx

Greetings. Very happy to be the new owner of a 2005 GX. I have only owned it for a few weeks, but I am in love with the power of the 4.7l and the quiet interior. I am Tacoma and 4Runner fanboy, but the GX is just in a whole different world as far as comfort.

All the love aside, I am having a problem with the rear suspension that I would like to get figured out ASAP. The rear air bags seem to deflate at random. The indicator remains at "N," and I can't change the setting without turning the vehicle off and on again. I pulled the codes with Techstream and got a C1761 code for a malfunctioning Suspension Control ECU. According the FSM procedure, if the suspension "OFF" light does not come on the procedure is to just replace the ECU.

Anyone else dealt with this code before? I hate to just throw money at parts, but the FSM seems to suggest that that is the only troubleshooting step.

Thanks.
Daniel

co4wheel

Many just ditch the rear bags once they start acting up. You could have just a simple leak in one of the bigs. Or any number of other things. Cost of items add up quickly. If you want just to get some coil springs back there call Metal Tech. Talk to them. They have FJ springs and a conversion kit you can buy. If it was just a leaking bag you could then put some leveling air bags inside those springs to allow the vehicle to self level under load and even raise up to the higher level. You would loose the lower level entirely. Not a huge loss IMHO.

danthemanx

Very true. I don't really care about the adjustable suspension at all. I was really just hoping not to convert to springs until I was ready to lift a little. I realize people have had many different issues with the rear suspension. I was hoping to find someone that had specifically diagnosed the C1761 code to see if an ECU replacement fixed the issue.

chitown40

See the attached file from the FSM. This is the ECU Malfunction diagnostic flowchart.

danthemanx

Thanks man. The FSM pages I have seen did not include that ECU power source testing. I will check on that.

It really does seem as though the ECU is opening up the exhaust valve at its leisure as the air bags stay filled overnight.

Anyone ever disconnected the power to the exhaust valve solenoid? I am a little hesitant to do so as I am not sure what other effects this might have, but if the bags are filled to the "N" level and remain so after disconnecting the exhaust valve, then might eliminate the bags as a leak source.

chitown40

Definitely go through the FSM and test the wiring/ECM as decribed. The areas in the rear tend to corrode and cause issues for almost all owners unless the truck spent it's entire life in a dry desert. You may find an easy fix if you're lucky. If you need to replace an ECM, ask around on here and on IH8MUD.com in the 120 series section as many owners have already torn out their RAS and replaced it with springs. There has to be one of them with no use for the RAS ECM - most likely someone doing a more extreme build than the typical coil replacement.

danthemanx

Strangely, the FSM that I was looking at was for the 2005 model year and did not include the testing for the ECU that was included in the pages you sent.

I've looked at the RAS stuff under the rear. No notable corrosion. I did unplug the exhaust valve and let it sit over night. Unless there is another air relief outlet, I figured this would eliminate any air releases from the system by a faulty height sensor or a faulty ECU. It sat for 24 hours. I came in from work the following evening, and the bags were deflated. I assume that I have a leak somewhere else as well unless my thinking on the exhaust valve is wrong.

I may just go ahead and scrap the system for coil springs. I was ok replacing the ECU or a air coil. I don't want to replace both and learn later that a height sensor has gone bad as well. I hope to have some time this weekend to pull out the air bags and take a look at them.