Curious Monaro speedo issue

[Capri_Ghia]

Hi all,

The analogue speedo dial on My '04 CV8 is behaving a little strangely. Over the course of a journey it starts to over-read the speed by anything from 5-10 mph to the point that when stationary the needle doesn't return to zero. Even when the ignition is turned off the needle stays high but when you restart the engine it resets to zero and the cycle begins again.

I use the car every day and it's quite random on the commute to work in that some days it doesn't happen at all, some days it's a little and some days it over-reads by a fair bit. The digital speedo on the LCD remains rock solid and close to the indicated speed on my sat nav so I don't think it's a speed sensor issue. All the other instruments in the cluster are 100% ok, it's just the speedo. Weird. Better over reading than under but it's a puzzle.

Has anyone else experienced this? Anyone got a fix for it?

Cheers.

[mfp4073]

I'm not much help I'm afraid, but the 04 cars did have problems with the speedometer doing crazy things. They were fixed with a software update and that sorted the problem out.
It might be worth plugging in a code reader to see if any fault codes have been stored, if that doesn't help I might still look at the speed sensor eventhough the digital reading works OK.
If you don't get any joy on here try Facebook if you can, I believe there are still a few owners on there.

[MarvinTPA]

This is one of those 'They all do that sir' problems. Mine only plays up if not used when the weather is damp. A good run and warm through solves it.

[SturdyHSV]

My Ute had some 'interesting' speedo issues, but this was because a previous owner fitted a bullet connector in the speedo input wire on the back of the dash, the dash wasn't particularly wel screwed down so the jiggling / vibration would cause all sorts of weird behaviour.

It might be worth popping the dash out and cleaning up the connector on the back of the cluster and checking the wiring looks tidy, just as a simple thing to do (it's only a few screws to remove the dash cluster)

[GSE]

My car does this now and again. I seem to recall that it is something to do with the ambient temperature and misbehaves more in cold weather. Possibly because in Australia they weren't able to do much cold weather testing! It's probably a dry solder joint or intermittent connector somewhere, but I've never had the courage to take the dials out and have a look. I just ignore it when it does it and eventually it clears by itself when the car warms up.

[DD3566]

My 55 Plate VXR does something similar, always under reads by 2-3MPH, so indicated 70 is more like 73

[RipGMH]

DD3566 said:

My 55 Plate VXR does something similar, always under reads by 2-3MPH, so indicated 70 is more like 73

Under reading is quite normal in Aus and usually done as we have speed cameras everwhere and you will be fine for doing 5mph over the speed limit in a 60 zone, 3mph on residential roads

Back to OPs issue, does the digital speed display match the analogue indicator? Try driving in diagnostic mode (hold mode + set on start up) with the speed displayed.
If it’s just the analogue dial then it’s wiring on that path.
If it’s both could be a speed sensor needs replacing

[vxr2010]

my 04 cv8 under reads too , again a 2 to 3 of mph , i think it’s after the 3.9 diff being fitted , i wondered why in a 70 mph others were going slower than me lol

[JAMESHSV1]

Capri_Ghia said:

Hi all,

The analogue speedo dial on My '04 CV8 is behaving a little strangely. Over the course of a journey it starts to over-read the speed by anything from 5-10 mph to the point that when stationary the needle doesn't return to zero. Even when the ignition is turned off the needle stays high but when you restart the engine it resets to zero and the cycle begins again.

I use the car every day and it's quite random on the commute to work in that some days it doesn't happen at all, some days it's a little and some days it over-reads by a fair bit. The digital speedo on the LCD remains rock solid and close to the indicated speed on my sat nav so I don't think it's a speed sensor issue. All the other instruments in the cluster are 100% ok, it's just the speedo. Weird. Better over reading than under but it's a puzzle.

Has anyone else experienced this? Anyone got a fix for it?

Cheers.

When in a stationery position turn the ignition on and off a few times to see if the speedo resets back to zero but do not start the car

[notransistors]

You need to take perceived glitches in the gauge pod seriously.
My car used to go in excess of 160 MPH at stoplights.
Engine temperature gauge would sometimes peg at maximum.
So, when the temp gauge and coolant level light tried to tell me that something was going on, I ignored them.
The driver behind purposely cut me off and let me know that I had been trailing antifreeze for blocks.
I had dropped the bottom radiator hose and was quickly running dry.
Second lesson here- never use replacement hose clamps from china.

[Capri_Ghia]

Thanks for all the replies.

This is an intermittent over-reading issue that seems to have no real pattern i.e. not obviously related to ambient temperature or damp. The car is used daily and all other electrics seem ok. Turning the ignition on and off does reset it to "normal" but only temporarily.

The software update suggestion is an interesting one. I'll ask Walkinshaw when it's in for a service in a month or so.

I was hoping to not have to take the dash apart but that'll be the next step.

Cheers.