Syvecs Forums

I have a Subaru Hatch STi and I recently got the S6GP PnP for the car.
From my understanding, to get the cruise control to work, I need a cruise control button and an input to a brake pressure.
I tried to get the Cruise control working by doing the following:
a) Fabricated a button (I'm using an aftermarket steering wheel) for the cruise control and connected it to the roll connector. (Cruise and Cancel wires)
b) From the ECU Harness (lets call it connecter B) I wired the cruise and cancel wires to the pins 4 and 10 of the 12 pin molex
c) Since I'm already using the Lam V, I wired pin 28 (B28) of connector B (Brake switch input) to AN4 via the 12 pin molex and set Brake Pressure (Front) input to AN4
d) In Sensors, I set up Brake Pressure (Front) in a way that if I step on the brakes, it should exceed the max brake pressure set in cruise control and it'll cut out.
Monitoring the input V values, I verified that the inputs are wired properly and proceeded to test to see if I can get cruise control to work.
Then I noticed something:
i) When I pressed the cruise control button, cruiseActive is still Idle and cruiseDisableCause is Lateral Acceleration (?!)
ii) I keep getting Voltage Limit and Voltage Range Errors for the Brake Pressure (Front). Then I realised that B28 is a 12 V output and AN4 is only a bipolar 5V input.
So at this point I presume that my problem is mainly (ii). So may I know if there's any PROPER way to convert the 12V input to 5V?
My current idea is this:
A) Get a 12V to 5V convertor (for USB chargers)
Brake input -> 12V in
ECU/Power gnd -> 12V gnd
5V out -> AN4
5V gnd -> sensor gnd ?!? (aka pin 10 of 12 pin molex)

I hope what I'm saying makes sense. If there's a better idea of getting the cruise control to work (e.g. carry a brick in the car), do let me know.

I can't comment on the finer details of the cruise setup but if I've understood you right....

...why not re-wire the brake switch so that rather switching to +12V it switches to 5V? It will be easy to modify the wiring to the switch to pick up +5V from that 12 way connector.

I can save you both a lot of grief.

Front brake pressure comes in on canbus through the can bridge. There is no need to put any further sensor or switch on the car.

The rest of the control can be done with a single ecu input, 3 switches (up/set, down and cancel) and a resistor network.

You should confirm that you are getting 4x wheelspeeds and brake pressure with NO sensors configured in the IO config. If you configure a physical sensor in the IO config it will override anything that's coming in on CANBUS.

Do you have any ABS lights present on the car? The latest JDM hatches will require a different code in the CAN bridge, something that was only sorted in the past few weeks. If you have a problem the ABS light will remain on, although the wheelspeed and brake pressure inputs will still work.

Hi Tim,

According to the Service Manual, I have to snip something to "inject" the +5V inside, which is something I'll like to avoid. But I've to admit it is a a simpler way of getting things done.

Hi Pavlo,

I just tried what you advised:
No sensors in IO config for wheel speeds and brake pressure.
No ABS lights on the car, but ever since Syvecs was installed I noticed that the hill hold assist doesn't work anymore and frankly I don't miss it.
I brought up the gauges for bpf, bpr, and the 4x wheel speeds, all at 1 Hz.
The 4x wheel spds are there.
BPR is forever 0.
BPF acts very strange. I assumed that if I stepped on the brake pedal, I'll get some readings. What I've got doesn't match what I'm doing with the brake pedals. It's 0 most of the time, and displays only 2 other values -> 3.93 and 7.87
I turned on Cruise Control and set off to try if ANYTHING works once again and is immediately greeted with the message saying "blah blah is advised you have at least one brake pressure blah blah"
To me it ain't a sign of good things to come.
I tried to activate cruise control and once again I got lateral acceleration as the disableCause.
I brought up the LatG gauge and it's showing -1.001 permanently. Is there a way to IGNORE the lateral acceleration? I've tried setting to 0 or some weird values in the Cruise control settings.
Or am I still missing something?

The brake pressure warning is basically advising that you use 2 sensors (ie front and rear, or front and brake light switch) to ensure that there is some redundancy in brake sensing so the ECU can be sure that the cruise control is disabled in the event of the brakes being used.

I assume you've read the extensive help on the cruise control that is shown in Scal? This should answer all your questions. It should be possible to ensure that the threshold is always higher than the LatG but it would probably be looking at an absolute value so I would set it to at least +/- 1.002

I would recommend you up the frequency of gauges for most diagnostics, 1hz is actually very slow and it would be easy to miss a lot of what is going on, 5 or 10 hz if text is used, up to 100 can be helpful if using trace displays. Without knowing what you did exactly it may be that you just captured two Bpf readings 1 second apart but it's more likely to me that there is a CANbus glitch in there.

I honestly can't remember if the Lat and long G comes in over can on the hatch, I can check when I'm back in the workshop as I have a hatch there right now.

I've tried again this morning.
BPF set to 5 Hz. The readings don't make sense to me. It shows 7 bar while I'm going at 60km/h on the road. That surely cannot be the case?
I've also set the Cruise Control threshold to -2.000 and -1.002, the cruiseDisableCause is still Lateral Acceleration.
Something doesn't seem to be working right.

Have you tried setting the threshold to +2?

I would imagine that for lat G it uses (or should do) and absolute figure otherwise it would ignore corners in one direction only, so I would go with a positive number.