Inaccurate Speedo Reading Fix

[Snooozy]

Hi all, I got sick of having to mentally adjust my speed for the 8% inaccurate speedo reading.

So I purchased a Jaycar speedo corrector, after it sat in the shed for about 2 months (can't rush these things) I finally got around to assembling it. For anybody that is handy with a soldering iron you will find it a straight forward build-just pay attention to the colour coding & position of the components.

Anyway after it sat finished in the shed for another month I got around to fitting it last weekend.

The hard part was finding the best place to hook it up to the speed sensor. In the end I went for the wire at the rear of the speedo.

To my surprise I found the shroud around the speedo comes off very easily-just give it a firm tug at the top & then the bottom comes out fairly easy. There are no screws holding this in. Unscrew the 3 screws holding in the speedo & there it is.
I would recommend disconnecting the battery by this point. If you remove the plugs from the speedo you may get an airbag light on permanently. (I found this out the hard way ) not sure if this is the cause but play it safe.

There is 4 wires to connect-earth, power signal in & signal out. I took power from the speedo power wire - Black/White (keeps the instrument fuse running the corrector) earth connected to the steel frame under dash & you will need to cut speedo signal/pulse wire - White/Blue & connect corresponding wire to each.

The circuit board was mounted in the recommended case & slides up under the front of the console out of the way.

When finished I grabbed the GPS & headed out the road to calibrate the unit - fairly straight forward. I set the HEX switch to 0 & the DEC switch ended up at 8 = 8% adjustment.

I must say it's nice having an accurate speedo at last. It now is spot on & can be adjusted with change of tyres or even just for wear.

A recommended fix.

I hope this is of use to others.

Photos attached

Regards Ian.

---------------------edit------------------------

my Triton is an ML, I do not know if the colour coding or wiring is the same on the MNs

[Snooozy]

more photos

[Snooozy]

last photos
(can only post 3 at a time )

I used link 1 & link 4 for the setup.

My Tri is an 09 ML 3.2 D manual

should be same for most models.

[ag9111]

How easy is it to put in a switch if you are running different size tyres all the time?

[Snooozy]

its possible but would be a lot of thinking involved.

you could mount the circuit board so you could access the current switches.

the way it is at the moment its only 4 screws to take the lid off & change it.

[NowForThe5th]

Great fix, Ian. Well done. I'm off to Jaycar to get one of these cos' I'm sick of having to do the mental calculation all the time too.

[Greedy]

What did it set you back?

[Snooozy]

current retail is $54.95


http://jaycar.com.au/productView.asp?ID ... BCATID=347

[NowForThe5th]

Greedy,

http://www.jaycar.com.au/productView.asp?ID=KC5435&CATID=25&form=CAT&SUBCATID=347

$55 for one, reducing to $49.45 for 5+ and I have a Jaycar Trade Card which gives me a further discount. These seem like a candidate for a group buy.

[Snooozy]

I work at a Leading Edge Computers store & we are an authorized Jaycar stockist, I got mine at trade.

If enough people are interested I can talk to the boss & see if we can work something out.


If you are going to do this mod please be aware, since I did this I have the airbag light on. I'm not sure of the reason as yet.
I unplugged several connectors in looking for the best place to hook it up. The battery was not disconnected at this point & may be the cause.
It may be that the speedo was removed while the battery was connected.

I also wired my spotlights the same day & unplugged several connectors while looking for the hi-beam signal wire.

I don't want anybody having any surprises.
Ian.

[Greedy]

The airbag light will come on if an open circuit is encountered associated with the "dials" fuse from memory. I had this problem when I removed the wrong fuse looking into dashboard lighting. The symbol for this fuse looks like a clock.

[ultimate]

If you wire the speedo corrector into the wires entering the speed censor at the rear of the transmission (so underneath the car) you won't enounter the problem with the airbag light as you are avoiding all the other wires completely.

[Snooozy]

Greedy,
did you have to go to the stealers to rectify this, or is there another way? I tried leaving battery disconnected for a couple of hours, no luck.

I am hoping that this is the problem. I checked the workshop manual posted on the forum & suspected this may be the cause. Otherwise I'll have to do a rewire as ultimate suggested.

Does the SRS system reset from the scangauge or is it a separate system?
I don't get any faults listed.

[Greedy]

I had a trip to the dealers to fix it. I was there trying to get a new clutch anyway so no hassle. Don't know if scanguage can clear the fault as I don't have one.

[Jitsukablue]

Nice post Ian, my spedo corrector cost over $1000 and isn't adjustable... bigger tyres Nice to know there's a product already out there.

[bendoon]

If you wire the speedo corrector into the wires entering the speed censor at the rear of the transmission (so underneath the car) you won't enounter the problem with the airbag light as you are avoiding all the other wires completely.

Also with wiring it up this way the correct speed is going to the ECU & etc. Should make the economy gauge work more accurate too ?

[Snooozy]

good news

I went for a drive to the stealer today RE the airbag light.

Turns out it was just because I disconnected the speedo connector.
Came up as an open circuit error, just as I was hoping.

Make sure you disconnect the battery at least a few minutes before unplugging connectors.

Or do as others have suggested & connect at the sensor on the transmission. I didn't do this because I didn't want to cut into wires in an area which could get wet & dirty, leading to corrosion.

As I have a GLX with no trip computer I didn't have to worry about adjusting at this point. If you do have a trip meter it may be better to connect at sensor, (just make sure you seal the wiring well)

On a different topic I'm off to the Mighty Murray river tomorrow morning for a week, First time towing the van with the Tri, should be a whole lot easier than the old Ford wagon. My wife will be up after work with the boat - can't wait

[johnnie5]

bigger tyres would solve it or how about just use a gps ??

i found now using bigger tyres and the speedo is spot on that i am now paranoid about speed

when it was always reading a bit over i didnt worry as i knew i was fairly safe

[brunopezz]

Johnnie5, what size tyres are you running to course your speedo to read accurate?

[brunopezz]

The economy gauge (centre dash computer) works independantly to the speedo. I checked this out by pushing the reset button while I was traveling at a steady 100kmh on my GPS. my speedo was off about 6-8% but my average speed after the reset was activated on the computer came in at 102km. so this leeds me to believe that the computer is accurate but the speedo is not. don't know if the odometer is with the speedo or the computer though.
Anyone else notice this?

[snowman]

for those of you contemplating the speedo fix irrespective of what tyre size you have note that the Scanguage II has a facility for speed readout that is fully adjustable from what it is being told.

so i just used a GPS on some nice straight road and adjusted the speed deviation on the scanguage until it was perfectly (within 1klm) of the GPS readout. you could easily work this out for different tyre sizes as well so if you had a weekday and weekend set of larger muddies you could note the different deviations and adjust it in about 10 seconds once you know what it is.

as you can have the speedo as one of the four gauges readouts permanently on display i just use this now and dont even look at the speedo. the other advntages are that it is always backlit so no more turning on parking lights in sydneys plethora of camera riddled tunnels and you get the benefits of the other scangauge outputs including clearing codes.

[RHKTriton]

I've been thinking about the speedo adjuster for a while now and after reading the ease of setting up its moving up on the list. A Scan guage will be first as more use generally.

After reading through this post this morning I did some tests on the Odm. reading over a couple of 10km stretches and the readings were gaining about a 50 - 100m every km. This suggests the sensor is a bit optimistic. This means all your economy tests are actually showing better than real life results.

I wonder what goes on with the speedo errors, as most cars I've had, have always been about 5 - 8% slower than indicated. Does give the manufacturer a bit of bias in favour of fuel economy figures if people rely on the cars instruments. The gov't gets the traffic slower and the country reduces fuel compsumption - what a bunch of crepe'. Has anyone ever noticed how they creep up on other vehicles when they set their cruise to the exact speed limit?

Re cutting the wires at the gearbox end, I have often used heat shrink tube over the solder joint and then a larger tube over this and injected some silicon sealer into this - giving a good seal. Alternatively, squirt some silicon into the heat-shrink and then shrink it and you'll get a good seal as well.

[did3.2]

The economy gauge (centre dash computer) works independantly to the speedo. I checked this out by pushing the reset button while I was traveling at a steady 100kmh on my GPS. my speedo was off about 6-8% but my average speed after the reset was activated on the computer came in at 102km. so this leeds me to believe that the computer is accurate but the speedo is not. don't know if the odometer is with the speedo or the computer though.
Anyone else notice this?

Brunopezz,
I have also noticed this. Set the cruise by the GPS then hit reset on the readout and sure enough exactly the same speed comes up as displayed on the GPS.

[Eelesy]

I installed the Jaycar kit a while ago

i took the speed sense wire from behind the speedo but i routed it all the way over to behind the glovebox.

played with it a lil bit but im still yet to go on a long trip and have the passenger adjust while i drive at a constant speed.

i have never had any issues with the abs light coming on.

[johno]

thanks for the write up on this one Snooozy...

I've been thinking about this for a while, since they recently started talking about the "tolerances" for speeding fines, i thought it was about time i did something about it.
My speedo was out by 8kms, so if i was doing 100kms i was actually doing 108kms (larger tires!!)

I followed your lead and did mine the same, i used the same links (1&4) but i didn't need to adjust anything else both the HEX dials are on 0 and it's 100% accurate with my GPS now.

Thanks again....
Cheers Johno