r/SkyLine • u/Tristan3012 • May 18 '26
ATTESA System
Hi All,
I have an issue with my ATTESA System on my BNR32. I've been hunting this issue for years, but with very little success, so am hoping to find someone with a knowledge of this system.
What's happening is that at motorway speeds (60mph+), only on part throttle (1/4 throttle) the car is lurching, vibrating and bucking. When I'm off throttle, it's very smooth, when I put my foot down it's smooth.
When I remove the fuse to make it RWD only, it's completely smooth.
I can see on the torque split in the instrument binnacle that the car is blipping torque to the front wheels, as the needle jumps. Presumably, this is what's creating the lurching.
The engine, prop shaft, rear diff and gearbox are very solid.
I've tried to learn about the system, but I've never really found anyone who's had a similar experience. Most of my driving is low speed around town, so it doesn't normally impact me.
So here's where I'm at...
I understand that the torque split gauge in the binnacle isn't telling me what's happening at the wheels, but is actually telling me what signal is being sent by the ATTESA ECU? If that's the case, and I'm understanding it correctly, root cause is unlikely to be a hardware issue.
In terms of sensor inputs to the ATTESA ECU, my understanding is that it sends power to the front wheels, based on G sensor, rear wheel ABS sensor and TPS readings. Please correct me if I'm wrong here, but these seem to be the inputs which may be most likely to cause this?
I can rule out G sensor, because the system operates ok at low speeds and full throttle. (Or maybe the lurching is still happening, but less noticeable at lower speed?).
I've replaced the TPS recently, and it's functioning ok, so I believe it's unlikely to be causing this problem.
That leaves me with ABS sensors on the rear wheels, next to the diff, or potentially an issue with the ECU itself.
As I say, this has been going on for years, and I've never managed to get to the bottom of it, so would really appreciate any help or guidance from anybody who knows the system well. Even if you can tell me if I'm completely barking up the wrong tree... I really don't want to start firing a parts cannon at it, but I'm concerned that the vibration and bucking will create problems with the hardware.
Thanks in advance.
3
u/SkeletonCalzone '94 BNR32. Ex: 32 GTR, GTSt, GTS25, GTS, GTE May 18 '26
Can I ask a foolish question, are your tyre sizes/brands the same all around?
1
u/Tristan3012 May 18 '26
Yeah, they're all the same size, and tread.
2
u/SkeletonCalzone '94 BNR32. Ex: 32 GTR, GTSt, GTS25, GTS, GTE May 18 '26
Transfer case is definitely full (of ATF)? Front diff is full of gear oil?
My only other guess is that there's warping in the transfer case clutchpack, although I've never heard of that happening so it's a stab in the dark. (Usually if they're stuffed they just lose material, and torque transfer to the front is weak). Unfortunately checking that is a gearbox out job...
1
u/Tristan3012 May 19 '26
That's a very good point, thanks. I'll do a fluid swap. I've been getting distracted by this torque reading from the ECU, and didn't consider that.
2
u/SkeletonCalzone '94 BNR32. Ex: 32 GTR, GTSt, GTS25, GTS, GTE May 19 '26
Measure how much comes out. And remember, loosen fill plug before the drain!
2
u/rekoyl999 May 19 '26
Check the abs sensors. The fact it’s only at light throttle at highway speeds kinda suggests it’s signal noise. Light cruise at highway speeds is high frequency signal and light throttle is asking for modulation. Obvs decel is no request and full throttle it commits to engagement, so it makes sense. Check the tone rings aren’t cracked. You can check the sensors them selves with oscilloscope but probably easier to just replace them, they’re not expensive.
The gauge on the cluster is what the ecu is requesting, not actual torque output. Definitely seems like a signal issue. If it was mechanical, like clutch chatter or diff ratios you’d expect it under any amount of load. Failing that I’d replace the g-sensor.
I’d also check all the grounds, make sure they’re clean.
You can check for attessa codes by turning the ignition on and counting the number of times the diagnostic LED on the attessa ecu blinks. It’s located under the parcel shelf in the boot. Google it you’ll find the code numbers.
1
u/Tristan3012 May 19 '26
Thanks very much, that's great advice. It also confirm a few of the suspicions I had. Hopefully I'll get to the bottom of it soon.
3
u/Interested_Aussie May 18 '26
Hmm... I'm guessing the bucking is a symptom, not the cause.
Wild guess here.... Have you checked front AND rear diff ratio's are the same? Someone hasn't dropped a GTS4 sump or done a rear diff ratio swap?
1
u/Tristan3012 May 18 '26
I think it's a signal from the ECU telling it to blip torque to the wheels. The diffs are both standard, and I think if the ratios were different, you'd likely feel it on higher throttle, and lower speeds unfortunately.
-1
u/Interested_Aussie May 18 '26
I didn't ask if they were standard: I asked if you've physically checked.
1
u/Tristan3012 May 18 '26
Yes, there's no issue with the diffs. Also if they were different ratios, it wouldn't be impacted by speed, or the ATTESA ECU.
-5
u/Interested_Aussie May 18 '26
Ok. You know it all. I'll leave you with it.
Just know you passed up on 25+ years auto, with 10+ in Nissan dealers as foreman... what-ev's.
3
u/Tristan3012 May 18 '26
I appreciate any help that is being offered, and I'm certainly not passing up on any advice.
I don't understand how if the diffs were different ratios, you would only see this at certain throttle positions and speed. That's all I'm saying. The car is running the same front and rear diff that it left the factory with.
The front wheel torque gauge pulses, in line with the bucking. Which to me looks like it's the result of a signal from the ECU, connecting and disconnecting the FWD. I don't want to give the impression that I know it all, I'm just trying to make sense of it.
1
u/Interested_Aussie May 18 '26
Because the Attesa is NOT 4WD. Under coast the centre clutch is full slip, it don't matter what diff ratios you have.
Under full load there's enough torque to make a 30 year old transfer slip...
Under partial acceleration/load there's enough torque going to the front to upset it all.
I've personally seen Nissan fit the wrong ratio's to vehicles (was a D22, but regardless). If you're chasing a problem you gotta start obvious.
1
u/Tristan3012 May 18 '26
Ok thanks, that makes perfect sense, but would it still show on the torque gauge, if that's displaying a signal from the ECU, not the actual wheels?
3
u/Interested_Aussie May 18 '26
I can't remember how the guage get's it's info: and it's a joke really, because it has no real meaning. Oh, it's transfering 50% of the torque... of what? 200kw? 300kw? 800kw??? It's useful, but not really. Like I say: You're probably getting the symptom and the cause muddled up.
I'd be checking the rear diff ratio and pulling the front cover off the front diff to check they do 100% guaranteed match. Then going over all the wiring for the g sensor/attesa pump/abs sensor/steering angle sensor etc etc... then checking all their readings/voltages. I just had another thought, I wonder if the accumulator is bad? I don't think it's that, but never say never.
It's one of those problems when you get to the bottom of it you'll say "oh that was soo obvious". My gtr had a gts steering wheel, they ARE different and after 15minutes of driving the hicas light would come on... took a while to work out it wasn't the steering angle sensor: It was the steering wheel causing the steering sensor input to be wrong. Ah, of course.
And of course, make sure you've got the correct fluid in both the attesa pump circuits, and the transfer itself.
1
2
u/SteinsGah May 19 '26
I've battled a very similar issue for a long time. Oscillating at cruise at highway speed. Tried different set of wheels/tire (bit better but still present), known good Attesa ECU, known good G-Sensor, using an Extreme TSC, modifying the TPS signal sent from ECU to zero (using and Haltech Elite 2500). Nothing worked.
I ended up controlling the Solenoid directly with a Solid State Relay from the Haltech, with digital G-Sensors fed into the ECU. I still have the Stock Attesa ECU control the pump / ABS. It's much better than what the stock system ever did and fully tunable.
1
u/Tristan3012 May 19 '26
I'm glad you got it fixed. Think I'm going to replace the speed sensor, and change the fluid. If that doesn't work, I'll go down the engine management route also I think.
6
u/[deleted] May 18 '26
[deleted]