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 Capacitors also cause tacho and speedo failures

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Hiace Master
Hiace Master

Number of posts : 716
Home City : Cambridge, UK
Model and year : Model: KD-KZH100G-MRPGT
Year: 1996
Colour: 4K1
Trim: FN42

Registration date : 2016-07-16

PostSubject: Capacitors also cause tacho and speedo failures    Wed May 23, 2018 9:47 pm

I'm tracing an issue with my tachometer as it sometimes decides to not work at all. While there is a small chance of a bad connection there is also another issue that has and does affect Toyotas that I have been discovering.

BTW because I had previously changed all the ECU capacitors I did check the tacho signal coming out of the ECU with a scope and it was a good strong signal so the ECU is fine, the fault must be in the contacts or the tacho itself.
Diagrams below for you to save and cherish.

Note there is a mistranslation to 'emission control' that should read 'engine control'.

The electronic gauges in the instrument panel also contain these leaky capacitors, and some are now failing. E.g:

This is just a heads up if you are or do have trouble in the future. I've already changed the caps in the engine ECU, the roof ECU but there are more in the Overdrive/Autobox ECU, the AC amplifier and the instruments too.

Here is a demo of a person repairing an older KZ1 ECU, looks squarer than mine. It makes a good point that catching them early is a good idea as the acid takes time to eat the tracks.
Personally I think he takes the removal of conformal coating too far, it's usually designed to be soldered through so as ling as you take care it's not an issue to simply leave on the board.

Also an in depth blog about ECU fixes and capacitors that claims that from 1996 the capacitors were fixed so it's just a bit of aging, not the old catastrophic failure afflicting pre 1996 ECUs. So if you have a 1996 on ECU I wouldn't worry too much, although I changed my caps there was on cap I removed with any sign of leakage so my sample of 1 agrees with this.
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