2005 2.5 Subaru DBW Cruise w/ Vanagon CC stalk

[vwlovr]

Ok, so I recently went subaru in my van and in my haste to get a subi I ended up with a drive-by-wire donor. Although I was a bummed about having the dbw at first, it's turned out great and my favorite thing about it is that it has cruise control built into the ECU, which is great since i REALLY wanted cruise and don't like how kludgy aftermarket cruises look in the engine bay.

I had previously tried to get a vanagon cruise stalk working with my zetec and an aftermarket cruise, but I never had any luck mainly because CV joint based VSS's suck and I managed to fuck up the wiring.

So, once I had my subi up and running my first priority was getting cruise working. The first step to that was getting a reliable VSS since the small car CV joint based sensor was turning out just as finicky as the zetec set up was. For this, i went with the fastforward speedPuls VSS...

https://www.fastforward.ca/vehiclespeedsensors/

--EDIT--
So the fast forward VSS worked, but ran too fast so the ECU thought i was driving at 100mph, which then disabled the cruise. So I ran the VSS signal thru this to allow adjustment to an accurate pulse rate...

https://www.summitracing.com/parts/dak-sgi-5e

That solution isn't cheap, but i still like it more than CV based VSS as I don't have to work about a rock or exploding CV boot ruining my cruise control.

--EDIT--

Once that was working, I set out to wire up cruise. I had the subi cruise control stalk and have seen people use that, but I really wasn't a fan of it. Since I had a vanagon cruise stalk I decided to use it, so I took it apart and clean it (using these excellent photos https://www.thesamba.com/vw/forum/viewtopic.php?t=677602 ) and tested all of it's switches.

So what you need to make subi ECU controlled cruise work is...

- a working VSS
- 2 subaru clutch switches (you don't need the double action brake switch,really any normally off pedal switch will work)
- vw or subi control stalk
- NO check engine lights (dbw cruise is disabled if there are any CELs)
- green LED (optional)
- some wires and patience

First here's a look at the 2005 cruise wiring diagram. NOTE any other year may be wired differently, this is ONLY accurate for a 2005 USDM 2.5 impreza based donor. That said with this, you should be able to find the diagram for your donor's year and use what I've learned to figure yours out....

This is pretty straight forward, but there's a few things to note. You don't need the dual action switch for the brakes as you don't need the 12v battery to switch to c8 connection to make cruise work. What's odd is that from this diagram it would seem like the 12v ignition fed side of the brake switch would work opposite the clutch switch (since one looks normally-closed and the other normally-open), but i found that's not the case. Either the brake pedal switch works opposite the clutch switch in the car or this diagram is wrong. I no longer have my donor car so I couldn't tell if the switches were actuated opposite each other or not. The upside is if you don't have the switches from the donor (like an idiot i didn't keep mine) you can just get two clutch switches which have metal threads and a common nut sizes compared to the brake switch which is plastic and has a wonky 12m super fine left hand thread (and no nut).

Anyway, let's look at the wiring in the van. Since I wasn't sure if my OEM switch would work, I first figured out how to wire the subi controller, so I've included wiring for both subi and van controls.

The van switch has minimal functionality because the van's on/off is a toggle not a momentary switch. So I co-opted the RESUME functionality to work as the ON/OFF leaving me only with ON/OFF and and SET, but that's fine by me since I don't need resume and the limited functionality is a fair trade off for an OEM look. I was tempted to wire an indiscreet momentary switch to work as the ON/OFF, allowing me to keep RESUME, but it just wasn't worth it.

So I won't get too much into mounting the clutch/brake switches but it's not very complicated and i'm sure there's other examples around. Basically, I made an L shaped bracket using some flat stock and made some stops on the pedals for the switch to press on. When the pedals are not in use the switches should be pressed, thus allowing 12v to the ECU to both C9/C10 pinouts.

I also wired an LED in the dash to indicate when the cruise is set. I have the GW foil replacement so this was a breeze since the bottom right slot was already wired up and all I had to do was connect the ECU wire to my cluster. I did add a resistor to the LED to dim it a bit so it's not as bright as the turn signals.

That's all there is to it really. Seems simple once it's figured out.

[[email protected]]

Sweet great writeup. Many thanks. Simple and very clear.

[vwlovr]

ok, so funny update to this thread. I had tested this on a country road near my house and all was well, but this past weekend I took it on a longer trip and soon realized a problem with my set up.

Turns out that fastforward VSS reads a bit too high for the subi ecu cruise. Basically the ECU thought I was trying to cruise at 110mph, when it was really only like 80mph and apparently subi cruise maxes out at 100mph. Since my test were all around 65mph it wasn't an issue, but sadly for my 12 hr round trip drive on 80mph freeways it was an issue

Using a CV mounted VSS or tach based CSS signal generator will probably work better for this set up instead of the speedo driven unit since they are closer to your accurate speed. Since I already have the fastforward VSS and still prefer it over the CV mounted versions I am going to attempt to wire it thru a Dakota Digital Speedometer Signal Interface, which should allow me to adjust the VSS signal to produce an accurate reading in the ECU (which I can verify via the scangauge). It's not cheap, and I'd rather spend it on something else, but at this point a CV based replacement would cost me $50-60 unless i roll my own and I like the Dakota Digital interface since it will allow me to adjust it to be very accurate.

One other lesson I learned was that having the scangauge is pretty handy. Since Subaru ECU controlled cruise craps out if a CEL comes on the scangauge allows me to easily clear them on the road. I had 3 CELs pop up on my trip, but all were glitch conversion related things, 2 for fuel level sensor or something and one for some other thing i'm not actually using. They may just be glitches in the Small Car interface board that suppose to suppress errors like that, but either way, they were not critical and easy to clear while driving with the scangauage.

[wesitarz]

So you have the fastforward 8 pulse version if it reads high? There's a write up about that for Subarus in the product info. If you still have the Smallcar CV ring with magnets you could get a barrel type Hall sensor (looks similar to RMW's proximity sensor) on Ebay (from China) for a few bucks.Some prefer the RMW set-up. Hook it up with a voltage regulator like a 5v (zener) and dial it in for the correct gap to the magnets. 5 pulse 5v. This is what I am going to do.
My early SC interface board was throwing codes for tank pressure and sometimes fuel level. The voltages were off and non-adjustable. I used a couple of potentiometers to dial in the voltages.

[vwlovr]

no it's the 4 pulse version (or should be) but it's on a syncro speedo. i knew i could have goes back to CV mounted, but i just really don't want to.

yeah my SC board is recent so that's annoying. what size potentiometers did you use? i have a handful of little 10k ones.

[wesitarz]

I used 50k maybe too big as a very slight turn makes a huge jump in voltage so maybe 10k are alright.

[vwlovr]

ha, i did the same with my 10k ones, i was trying to add a pot to adjust the temp sensor and should have gotten 1k pots, because 10k was either nothing or too much

i'll have to dig up the pinout specs to figure out which is which and what to aim for voltage wise at least it's not constant and the scan gauge makes it a minor nuisance instead of a huge pita, but would be nice to prevent it so i don't get panic calls from the wife when the CEL trips on her.

[kbeefy]

Thanks for the writeup VW.... I've been wanting to do this for a long time.
2009 DBW 2.5 w/ CV SS
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86 syncro CHC, NorthWesty subbie 2.5, decoupler, locker, custom interior, 225/75r16 Duratrack's on CLK's, Toyo cabin heater, ARB fridge, 300w Zamp Solar, Gowesty bumpers/skid/rails, Fiama awning

'86 Syncro Westy. Stock for now.

2000 F350 7.3 CC LB 11' Northland Cabover

2006 Subbie OBXT

2002 Tacoma DoubleCab 4x4

1969 Mustang Basket Case 351c/FMX/9

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