Trouble in paradise - Active suspension acting up

[No1Dad]

The 95 Q I bought from Jay has been my pride and joy for the brief while I've owned it, and rightfully so! I've been fixing or at least looking into the very minor issues that persist like tie rod ends, an alignment, etc. Kudos to Jay for such an exceptionally well kept vehicle. However I noticed last week that there was a groaning noise near the front left wheel. At the time I even thought that I needed to hit my rotors with the honing tool. However I did just that this weekend and the noise persisted. Obviously this was not your run of the mill brake pad noise.

Now, I'm aware that the active system compensates for the front end dip when you come to a stop. So it didn't occur to me until today that it would be having problems. And boy did those problems begin to snowball as the day went on. It's Easter Sunday so I had a few social events to take care of and driving the 95 is my favorite weekend activity. Needless to say I wasn't going to cut the day's events short over what I thought were noisy brake issues (verified the pads had plenty of meat left).

I am ashamed to admit that no, I haven't done my homework on the active system and my overpriced scanner doesn't even have functionality past the data stream/codes for engine and transmission. This was not an issue for my 90 as it is bare bones but I was bitterly disappointed when I hooked it up to the active and found the same basic functions. I have not looked into the options for other scanners either but I'm curious to know what you guys use.

Back to the issue at hand, later in the day I would take a slight bump or dip in the road (not a pothole) at lower speeds (maybe 20 to 25 mph) and there was the same groaning, almost like a scraping noise that can be heard at the front/mid left of the vehicle nearly underneath the driver. At first I had been scared thinking I bottomed out somehow, but I was going down a road I had taken before without problem so that doesn't make sense.... by the time I got to my destination and eased her into the driveway I heard the groaning noise again, this time at a complete stop immediately after turning off the vehicle. Then I felt/saw her start to lower within seconds of being off. She has never immediately dipped low like that, so obviously that was cause for alarm.

On the way back home just a couple minutes into the drive I see the ACTSUS light go off. Ouch. The ride quality immediately went down the gutter but she made it home alright. Unbeknownst to me she also had this trans code (01).


I had to do a self test and this came up. I read it as code 51. The service manual states that only 1 code (the most serious) will show at a time for self diagnosis. And that about covers it.... I'm in the process of figuring it all out as we speak. Below is a gif I made of the code flashing incase my interpretation is wrong. In the mean time I'll start digging into the service manual and looking up which software is best for the Q. I looked for Consult scanners on ebay, I remember seeing a few listed for $400-$750 a while back but there are none available at the moment.

https://imgur.com/DUI1Ata

[No1Dad]

I've ordered a consult to USB adapter. While that is on its way I decided to check the alternator as I have been told (and read) that the system is finnicky with low voltage. The output starts at 14.2 when cold and slowly drops to an average of 13.1 after about 20 mins of driving. It dipped as low as 12.9 at times. Needless to say that's the first thing that has to get taken care of. I think its strange that the IP never set a low battery message. Hopefully that resolves my issues for the time being

[Q451990]

I've ordered a consult to USB adapter.

Which one did you order? I think mine is dead. Of course, it's getting plugged in to an 18 year old laptop running Windows XP, so we have multiple opportunities for problems.

[Infinitiguy19]

The noise could be air in the system or the main relief valve operating in the multivalve. You can try to bleed the air from multivalve. which is where you are describing the noise is coming from.

Active code 51 means engine stalls during driving.

As far as the abrupt drop when shutting the car off does it raise up quickly when starting as well? You could look at the flow control valve in the multivalve. First check the bypass screw in multivalve and make sure it’s completely loosened out and jam nut is tight.

Or as far as dropping when shutting the car off goes it could be some debris stuck one of the check valves part of the multivalve. You could try the flush procedure listed in the service manual. That basically runs everything through the filters at a greater flow rate than normal.

No filter in my opinion is lifetime like Nissan thought when they built this system. There is one part of the fluid tank and one in the multivalve that has no replacement available. The one in the tank I used a Mercedes Benz active body control filter and housing modified of course to fit in the Nissan tank. There are also metal screens built into the pressure control units.

[No1Dad]

Is there a general consensus on what the alternator output should be? I know the service manual is supposed to be the bible for these vehicles but during my research I've seen numbers across the board.

Just as an example, Q45 tech states 13.2 V @idle is "normal", Jay says 13.8V+ and the FSM (EL -17) states 14.1 minimum


I want to get my voltages right before digging into this any further.
Today I put in a supposed "Hitachi Reman" spare that I had. I was on the very last step of the installation (connecting the battery) when I jiggled the terminals to check for a snug fit and the positive post was loose as a goose. Mind you this was the battery itself, the entire post was spinning it wasn't just the terminal connections. Pretty sure thats not supposed to happen so she also got a brand new battery today. After all that I'm sitting at 13.5-13.6 V hot idle. Obviously this is lower than ideal but I'm wondering if you guys considered it acceptable. I would be open to have the old alt tested to see if the battery was the culprit the whole time.... Not looking forward to swapping it back in but thats what you get for cutting corners/ skipping diag steps.

One thing to note, I did take the time to check out the cables and grounds, shes clean AF

Active code 51 means engine stalls during driving.

Yes, I did see that code 51= engine stalling. I did not perceive any bogging/stalling when the fault occured. I first noticed the ACTSUS light/failsafe mode activating while cruising on the interstate. Hoping it's just an open circuit and not a damaged ECM as the diag tree suggests (FA-80). BTW re-checking ACTSUS codes comes up with 55. This was after 35 miles with the new battery and alt. According to this post by the previous owner that was a known fault. I assume this means I'm back to "regular" operating conditions?


Bingo! It was in fact also rising quickly on startup. It was cold and raining today (low 50s, high 40s), and I did not notice this happening at all. When the failure occurred last weekend the temps were mid 80s. Could this have an effect on the system based off of fluid condition/viscosity? I have not checked the coolers' condition.

The bypass screw and its lock nut were not the issue.

Thank you for the air bleeding and filter suggestions, this system is a lot to take in at once. I appreciate the guidance.... Will report back with findings.


I've decided to use ECUTalk to start and I bought the cable on their website. I believe you can emulate Win XP and other previous versions on Win10 in case you were worried about upgrading and compatibility. I assume you already have the USB drivers configured?

I've ordered a consult to USB adapter.

Which one did you order? I think mine is dead. Of course, it's getting plugged in to an 18 year old laptop running Windows XP, so we have multiple opportunities for problems.

[Infinitiguy19]

13.6 volts or close to it is normal. The problem is that the active computer uses 3-4 small power wires and they go from the battery to the trunk areas through a couple of connectors. Going through connections costs you some voltage due to resistance.

Weight and temperature does affect the suspension but not in a crazy amount.

[No1Dad]

Update:
I received the ECUtalk cable a few weeks ago, BTW the program and cable/drivers work fine on Windows 11. The 90 got wrecked the day I was supposed to pick up the 95 and start diagnostics so I've been hesitant to get her back on the road until this weekend.

The reman alternator failed this morning as I was playing around with the ECUtalk settings! I didn't even get 100 miles out of this thing before it died. I popped the old alt back in and it still has output voltage dropping @ operating temp so I will need to find a suitable replacement......


If you were in my shoes would you:
A. find and try another "Hitachi reman"

OR

B. Roll the dice with a local parts store alt?

BTW shoutout to q45tech, dropping the compressor to get at the alt is way easier than taking it out from the top. ~45 mins is the time to beat (not including AC recharge). I'll check back in after prepping some data logs to share and completing the steps you have outlined. Thanks again for the interest!

[Q451990]

45 Minutes! It took me 45 minutes to just figure out how to get the top bolt on the back of the compressor out. Maybe more than that.

I just replaced my alternator with a Hitachi reman that I bought about a year ago. Also getting about 13.6V at the battery. I hope your experience isn't a bad omen. I'm hopeful that because my battery was fully charged, the alternator ramps back a bit? I topped it off while it was out of the car and let it sit on a float charger for several days before I put it back in.

Where did you buy your alternator? Do you mind posting pictures of it?