NB SE Tacho and Odo stopped working

[Nevyn72]

Not sure if this will help, but may be a starting point...

http://www.mazda-speed.com/forum2/index.php/topic,13896.0.html

Nice find Tony!

Hate to say it Kev, but it looks like an ECU issue of some kind.....
Try these in order;
1) Disconnect battery for a long while and try again.
2) Check wiring around the ECU for splits/fraying/dodgy insulation etc.
3) Borrow another SE factory ECU and see if that works
4) If the factory ECU is cactus, buy an aftermarket ECU and enjoy better performance & drivability!

[KevGoat]

Oh cool ... thanks for that Tony!! Yeah, I disconnected the battery earlier. On a side note, when I did that, I realised too late that I don't have a battery siren key

Yeah Nevyn, there are a few pointers in that direction now. Will check how to get at it and have a look. Not sure when I'll get back to it, busy next few days. Really don't want to go aftermarket if I can help it though.

Just finished testing the continuity of the circuits on the back of the cluster with a multimeter - googling and learning as I go, as I've hardly ever used one before! Continuity seems ok on as many tracks as I could check. Though it's more like a component shutting down after a period of current flowing than a broken circuit, as it works for a short time after I unplug and plug back in that one connector.

Ah well ... time for a few glasses of red me thinks ....

[Roadrunner]

Hmm when my speed sensor died I lost speedo, not tacho. And the odometer stilled showed up on the dash, it just didn't tick over.
You have a connectivity/continuity issue there. Check all the tracks on the cluster circuit, they can wear down where the three plugs clip in.
Good luck

[KevGoat]

Thanks Roadrunner ... yeah have checked all the tracks, even used a magnifying glass to really see them, then later this afternoon used a multimeter.

I've been having a good think about all this tonight, and I reckon this issue may have started right back on our Canberra trip a few months ago! We had damp, icy conditions for much of the trip. On the last couple of days, we stayed in Echuca, and the car was parked out in the open., it didn't get moved at all. There was a lot of rain, especially the night before we left. The morning that we left, I started the car and switched on the lights and the instrument lights all flickered - I commented about it to my wife. They came right and I didn't think anything more about it. Then a while ago, I had a strange issue with my remote not unlocking, locking any of the doors or the boot release. Nothing was responding at all - boot, lock, unlock. It only worked when I put the key in the ignition. It strangely solved itself when I removed the remote battery and then put it back in. And - now this has happened.

From reading some wiring diagrams I found online, the one common between all of these events, is the earths under the headlights.

Unfortunately, I couldn't find these earths today, and further reading shows that I need to remove, or at least loosen, the front bumper and completely remove the headlights to get to the earth points!! Also read one person's thread where he moved both earths to new locations so that he could access them easier if required again - as I'm taking all of that apart, I reckon I'll do the same whether it's the problem or not.

Ah well, good practice for when fitting larger intercooler ...

[davekmoore]

Speedo on my SE became unreliable. When some of the oil leaks from the motor were temporarily repaired it started behaving properly again.

I have a spare SE ECU if you need one.

[Tony]

Did water get in or around the ECU? Maybe some connectivity/earthing issues in that region.

[KevGoat]

Thanks for the offer Davekmoore, hopefully not required

Tony - yeah, I'm still going to check around the ECU, just in case moisture seeped in.

[Okibi]

Wouldn't hurt to give the gauge cluster connections (and plugs) a good clean with non residue contact cleaner, could even rig up a few extra earth-return wires to try and eliminate that from the equation.

[KevGoat]

Rigging some extra earth's - one of those "why didn't I think of that" ideas! Thanks Dave!

[KevGoat]

OK ... this morning went out to Jaycar and purchased some proper contact & circuit board cleaner. Gave the whole thing a good clean, especially the contact points where the plugs go in.

Then made up some earth cables.

First, just plugged the panel in to see if the cleaning had helped. For a while, I thought maybe it was good, but, maybe because of the colder conditions today helping it last longer, it eventually went off again. This particular time, I noticed a slight revs rise, maybe 100/200 revs, when the instruments died - no idea if relative.

Attached the earth leads I'd made following Okibi's idea and attached them to a good earth. Once again, seemed to take a reasonable amount of time, but then happened again.

A couple of times today, after switching off ignition then back on, the odo returned, however when I started up it all died almost instantly.

So ... on to the ECU. When I first lifted the carpet I thought this might just be the culprit. Bits of rust around the bottom of the cover! Time to take it off and see inside. WHAT A B*$T*RD of a job to get to that little gem!!! Rather stupidly, I eventually lost patience with the dremel and thought I'd use a grinder ... umm not a good idea (even with plenty of cover shielding placed everywhere) ... carpet underlay stinks when smoldering So, back to the slow grind and trying different bits in the dremel. Finally got there - and here's some photo results ....

The rust around the base of the cover - looked worse in the car! Looks like some moisture has been running down the outside left edge, then collecting along the base. Not bad considering a convertible though. No rust or corrosion on the floor of the car, only on the lid.


The very clean and dry ECU ... all the contacts and wires looked good.


Decided to spray some KillRust on the cover before it goes back in ...


So ...

I have checked the instrument panel PCB for dry joints (this is a lot what the fault appears like)
I reckon I can now pretty much rule out earthing problems (thanks again for that idea Okibi)
I'm pretty sure I can probably discount the ECU. I unplugged the ECU and plugged it back in and it made no difference to the instruments (unlike unplugging the one connector on the back of the instrument panel).
It appears to be something relative to Plug 1 on the back of the instrument panel. This is the only plug that makes any difference. Unplug this, plug it back in again and things reset and stay on for a little while, especially if wait for a while before doing it (as if something is cooling and re-gaining contact)

When I took the instrument panel out again this morning, I noticed that the area at the back of the panel around the area of the odo was warm - no idea if this is normal? Probably just the microcomputer?

I have checked all the fuses - but am considering going through and just replacing them all to see if by any chance there's a faulty fuse that isn't blown, but is losing contact as it warms up (highly unlikely, but grasping here)

Starting to think I need to source another instrument panel to plug in and see if same happens ...

[thegarts]

Speedo on my SE became unreliable. When some of the oil leaks from the motor were temporarily repaired it started behaving properly again.

I have a spare SE ECU if you need one.

So there's no issues in swapping ecu? i.e immobiliser etc

[KevGoat]

So there's no issues in swapping ecu? i.e immobiliser etc

I was reading up in that last night just in case ... there seems to be a few issues from what I read. Keys & remotes need re-programming to match the ECU, as well as the ignition lock needs to match these. Central locking module is also apparently individually linked to the ECU and the immobilizer is also affected. Not the simple swap I thought it would be, being stock. Not sure if any tricks to doing all this, but if it has to be re-programmed by Mazda, the costs would justify going aftermarket and gain the benefits - although reading the issues that happen as well, I'm not keen on going down that path.

Luckily, I'm pretty certain it's not the ECU. At least I can get to mine easily now

[93_Clubman]

Does that underlay below the ECU extend down far enough to wick away any moisture collecting at the base of the ECU cover? If so, you might want to pull it up a little to avoid any possibility of that happening.

[bruce]

I'd still say ecu.
It would be good if you could swap instrument clusters to rule that out.

[JBT]

I think the instrument cluster is the issue. Seems like something in the circuitry is heating up and causing the failure.