Aftermarket Head Unit - connecting vehicle speed pulse line

I was contacted by Andrew, Technical/Customer Support, Aftermarket Support Co-ordinator, Alpine Electronics of UK Ltd. via e-mail last night with the following:

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I have some information on the speed signal requirement for you, And also some info on where to pick up the speed pulse if it relevant to your vehicle.

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Attachment 151626

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It took them a while to reply (over a week), but far more useful in the actual information provided than either Alpine Australia or Alpine USA were (have to wonder why either of these couldn't access this information?). Still no technical specs for the input (i.e. maximum input voltage) but the fact that there's an Alpine sheet specifying which wire to use for the input is more than enough - I'd therefore suggest this is problem solved and can apply to other aftermarket headunit installations into the D2 too.

I only noticed yesterday that there is a vss input wire on my aerpro harness , everything works as should so I'll leave it as is.

The only problem is that the information from that Alpine sheet is not for D2 but for for a D1(MK1, LJ) as the photo is cropped from a D1 RAVE and IMO the information is not accurate cos that connector(C209) has 20 pins(the two blanks are not pins) and the VSS signal in the Y/K(yellow/pink) wire is in pin 17 not pin 2 while what's pointed as pin 2 it's pin 13, the VSS on the D2 is pink/green wire all the way from the ECU through all tye headers and to all the systems and doesnt go through such connector under the steering wheel.

connector layout from D1 RAVE, VSS (YK wire) in pin 17 is confirmed by the diagram too believe me, only on early D1s YK is present in pins 18 and 19 .... i'm wondering what kind of job are doing those guys there though [bighmmm]

Once upon a time I worked for an Alpine Dealer, I can say that their tech support was top shelf, ring the number, speak to an actual guy on the other end of the phone that knew his ****. Propper techy stuff for the installer.

Tech support asside, WHY would U even need the VSS wire connected, australia has about 2 tunnels where you actually loose GPS signal. Not even worth the hassle.

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Originally Posted by CU55TM Disco

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Tech support asside, WHY would U even need the VSS wire connected, australia has about 2 tunnels where you actually loose GPS signal. Not even worth the hassle.

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First thing I thought too, but the OPs concern is that if not connected, does it continually nag you that it's not connected, and if it does nag, can it be turned off .. etc.

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Originally Posted by CU55TM Disco

WHY would U even need the VSS wire connected, australia has about 2 tunnels where you actually loose GPS signal. Not even worth the hassle.

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It's not necessarily a need at all, but rather for the sake of connecting one additional wire and having full functionality, why not? I don't see the connection itself as much hassle but sadly the tech data required defiantly is.

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Originally Posted by AK83

First thing I thought too, but the OPs concern is that if not connected, does it continually nag you that it's not connected, and if it does nag, can it be turned off .. etc.

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Id hazard a guess at no.

I know that if U remove the VSS wire from factory Toyota Nav units, U can watch movies on the go ;-) with no pitfalls.

Back in the day the OEM Blaupunkt units that we fitted to comodores had a VSS wire, and the sales guy used the same pitch, So the unit knows where U are if your in a tunnel, jesus, back there I think there might have been ONE tunnel in the country, and it only had one entry and one exit LOL

The only other thing the VSS might be used for could be Speed Sensitve Volume Ctrl, which in itself can be a pain in the rectal region.

Wow, you would think Alpine could just manage to say it's tolerant up to X volts (I'd expect X to be up to about 16V) and put it in the damned manual.

Must be some nifty code to be able to take the potential variety of VSS signals and derive actual speed, PWM, Frequency related, Voltage and for full joy current sinked formats spring to mind.

This level of technical support seems pretty common, a mate on here bought a thingy to connect the D2 steering wheel controls up and they sent the most stupid responses for technical questions.

Leave it disconnected, it's not a massive help....

Oh, I'm pretty sure the signal is actually a 50% duty cycle variable frequency, different than PWM which has only a single frequency and varies the duty cycle (that format is used on the SLS signal).

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Originally Posted by sierrafery

The only problem is that the information from that Alpine sheet is not for D2 but for for a D1(MK1, LJ)

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Wow, thanks for pointing that out! I hadn't checked against the car or Rave so wasn't aware, just assumed that they had provided the right information.

I've never heard of a Discovery 1 being called LJ model before. Is that a common reference for it? Is there such a code for the Discovery 2 - I'm aware of L318 for it?


I printed that sheet out and took it into the local Alpine dealer. Had a chat to them, showed it to them and asked if they had access to such information as this was the earlier model Discovery and I wanted to see if I could get a copy of the sheet for the Discovery 2. The guys response was that Alpine doesn't have that sort of information as they don't know all the vehicles and wouldn't provide that incase someone follows it and something goes wrong. I then pointed out that the sheet was from Alpine, and pointed to the 'Alpine' logo at the top which just go an 'o' and 'don't worry about connecting that wire it's just for tunnels anyway'...

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Originally Posted by twr7cx

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I've never heard of a Discovery 1 being called LJ model before. Is that a common reference for it? Is there such a code for the Discovery 2 - I'm aware of L318 for it?


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Yeah, LJ for D1,

LT for the D2.

It's part of the VIN number.

They start off SAL(mostly) then the LJ, or LT
You having a D2, your VIN will be SALLT ... etc, etc.