Strange behavior speedometer

[Ganglylamb]

Hi,

Yesterday I was riding my pcx just fine until all of a sudden my speedo was indicating 0 km/h while I was easily going 90 km/h. Next it started going erratically from 0 to 140 back and forth and sometimes just kept sticking at a certain speed.
Has anyone ever had a similar issue and does anyone know what I should be looking for? I think its probably just some dodgy electrical connection which I would have to clean/spray with some electro spray but then again I am not sure where the wires of the speedometer are located exactly and I do not want to go through the hassle of removing all panels just to find out I removed the wrong ones .

For the rest it rides fine but I already have some speeding tickets on my name with the PCX and my butt speedometer is not calibrated good enough - and just keeping up with traffic is what got me the previous speeding tickets so a correctly working speedometer is a nice feature .

Thanks in advance,

Ganglylamb.

[Conelite]

Check battery terminals. Make sure they are tight.

[Ganglylamb]

Check! As tight as they can be.
I should note that after some kms I was able to get off this national road and shut down the engine - restarted; it was there again but after a couple of restarts it seemed to be fine. Rode another 30 kms after the incident and haven't seen it behaving like that again. So maybe it was simply a glitch just like my indicators which sometimes don't work (still need to bring it to a Honda dealer for the free recall on this issue) and after a full restart they magically work again...

It's not like it's a showstopper but it certainly was a distraction while riding - and I'd like to keep focused on the road and environment.

[Conelite]

Could be a loose connector or something. I would give it a once over the dash. Reach in by where the forks go up and make sure everything is secure.

[Ganglylamb]

Well glanced at it, all seems to be secure. Rode home today from work going 0 km/h for the whole time. Never saw the fuel consumption that high as it does sees fuel being consumed but no kms are recorded of course...

I checked the service manual and next thing is to check the VS sensor as its the least amount of work to get to. If that is good I will have to check for continuity between the speedometer 20P connector and the VS sensor 3P connector. But this is where it gets confusing as the manual states a 20P connector while my after 13' model should have a 16P connector going to the so called 'combination meter' which includes the speedometer - at this point I guess a typo in my manual (hopefully).

Anyhow to get access to the 16P (or 20P - will see if I get there) connector I should:
* remove front meter panel
* * remove front cover
* * * remove meter visor
* * * * remove front grille
* * * body cover
* * * * center cover
* * * * * remove seat
* * * * remove grab rail
* * * * * remove grab rail cover
* * * right inner outer cover
* * * * remove left inner outer cover
* * * front center cover
* remove handlebar front cover

A lot to remove to simply get to an electrical connector properly .

[Ganglylamb]

Ok I think I found what was wrong - that is I just rode 50 kms without any issue.

20210824_223223 (1).jpg (229.37 KiB) Viewed 2734 times

This is how my lid cover is now in place. Notice the cable coming out which states lonelec - some years ago I attached this cable in an attempt to be able to connect an ODB thingy to it to connect to my smartphone. After a disastrous failure (read the details here ) I just left it at that and removed the bluetooth obd adapter but left the cable in place and closed the battery lid cover. Obviously as you can see in the picture it was a tight squeeze and the cable got pinched a bit. No problem - until now.

It was when I inspected the battery connections as Conelite suggested and after opening it back up (after reading the service manual and decided to go all electrical) I noticed the cable was quite flattened where the lid was squeezing it. I tried to remove the cable before my previous post but it seems quite difficult to disconnect, so I cut out a small piece of the lid cover so it does not squeeze the cable anymore. And ... well the problem seems to be gone for now - so my assumption is the cable is causing a milli-amp bonfire among the 4 connections inside this cable and messing up my PCX her brain.
So the next thing is to remove the cable entirely again, and put the red cover as seen in the picture back on the other end and be completely done with it.
If this was the issue, then the problem was with its owner and there is nothing I can blame my little PCX .

[Conelite]

If the cable is not connected to an OBD reader, why do you even have the cable connected to the bike? Im so confused. lol

[Ganglylamb]

Because I'm lazy and removing the cable proved quite a bit of hassle as I had to remove the battery to get easy access to the connector . Some say laziness brought the Roman empire down - if all holds up it also brought my PCX down :-D.

[Ganglylamb]

Well the problem returned so it was not that cable.
I got to the VS sensor quite easily (remove air filter cover) and the air filter housing bolts, lift up the air filter a bit and loosen the VS sensor protector cap and give it a good wiggle to get complete off. There was some iron like gritty deposit on the sensor, I never saw this when I changed the final drive gear oil but somehow it sticks to the VS sensor. Anyhow I cleaned that off installed all again but no success.

I also noticed on my test ride afterwards my fuel indicator went from 1 bar to 3 bars while riding on a flat surface (have seen in the past it sometimes adds a bar with in or decline of road)... I inspected the wiring diagram in the service manual and the Green/Blue (G/Bl) cable which goes from the VS sensor is also shared by the fuel indicator system.
The whole G/Bl wiring also goes to the side stand switch so even though it runs fine and starts fine I might inspect and clean the side stand switch as a next possible cause just to be sure.
A new VS sensor is around 85€ here (including shipping) so I hope I can at least determine where it is coming from first before buying a VS sensor which in the end I might not need.

[Ganglylamb]

Just an update; got to the 16P connector (took some shortcuts as I did not remove the front side cover panels) and performed all things stated in the SM (had some help from my wife as I could not connect my multimeter terminals at both the front and end of the bike at the same time) and I have ended up at the end:

speedometerSM.png (82.66 KiB) Viewed 2698 times

I also checked all the other electrical bits there are to check according to the SM at the 16P connector and all turned out fine.

So I guess I'll buy a new VS sensor install it and see how it goes - bummer though the official honda parts dealer for Belgium is on holiday until 31 August so it might take a while before I get my new sensor and post another update on this.

[Ganglylamb]

Quick update: rode to work today without the speed sensor working (again 99.9 l/100km on the display ), MIL light came on.
Stated the DTC code for MAP sensor low voltage somehow... Only happened with strong backwind and probably -as the speed sensor also acts as as rev limiter I got beyond the normal maximum revs as I was going WOT at that time and then the MAP sensor started acting up.
Going back home the wind was still from the same direction so the check engine light never came on as I never reached those high revs.

So untill I get my new speed sensor I'll take it slow and certainly won't go WOT again.

[Ganglylamb]

Update: finally got my new speed sensor - took out the old one and in with the new in about 15 minutes (did not bother following the instructions in the SM and took some shortcuts so I did not have to remove the air filter housing completely).

Did 2 test runs each 50km and so far no issues yet. When inspecting the old sensor up close the middle pin of the connector (which relays the signal) did show some corrosion so the issue might have come from that - I guess that's what you get when riding during rain a lot...

In the end still glad I did all the other checks as stated in the SM to make sure there was no faulty cable or anything because the new sensor was 75€ which I do find a bit steep for such a simple component and else it would have been another shelf decoration in my garage .

[Ganglylamb]

I know it's an old topic but still - update: speedometer died again 8 months ago with the same symptoms (needle going to all places and finally it simply died). Replaced the sensor as before - should have checked continuity for the cables as the SM says before replacing but hey simply replacing worked before right?
No luck this time.

As I just got a new 2023 PCX and now have a backup I decided to tackle this problem so I stripped the bike of all the panels and finally found the culprit:

sensor cable.jpg (115.51 KiB) Viewed 2003 times

This is where the three cables going to the sensor are located in - if you look closely you can see a bit of copper sticking out. This part of the cable runs behind the air filter box. When cutting the sleeve I saw 2 of the 3 cables being broken at that spot.

sensor cable2.jpg (95.06 KiB) Viewed 2003 times

I stripped all 3 of them (the one which was still working only had half of the insulation left), soldered them back together and now the speedometer is working fine again.

I also noticed closer to the engine that the sleeve in which these 3 cables run was halfway gone (probably due to friction etc.) so I wrapped the whole thing in some duct tape to prevent further chafing.

So for those who have a broken speedometer - first perform continuity test as described in SM. If those fail look behind the air box first , the rest of the cable goes into the main wire loom and seems to be holding up fine with no chafing present.

[mymitzi]

Good job..........Thanks for sharing. Just might help someone else.