Electronic Fault? Can Anyone Advise

[Futuramic]

Today I got into my Toyota Corolla (1998 4A-FE Liftback, manual) to drive home from the station. I put the key in and turned it. Nothing. Tried again. The dashboard went haywire, needles pulsing as if to silent drum and bass. Then nothing. Again, same needle issue; the engine turned sluggishly and burst into life. After that everything seemed to work. Everything except the tachometer. I tried turning the car off, but the same result. It seemed as if the tach wasn't receiving an input signal from the ECU. The dashboard is fully electronic on this model.

I got home and performed an ECU reset AKA disconnecting the battery for five minutes. All is now fixed and I have revs! The counter works as normal.

I have checked the manual and it mentions having two ignition keys on the same ring is a bad idea. I was doing exactly this. It can cause transponder issues, in that the ignition barrel picks up conflicting signals.

I have removed the other key from the ring. Is my problem really that simple? Or could it be a sign of a weak battery. I think the failure to start was caused by the immobiliser not disarming.

[jmcc500]

Have had similar symptoms when battery low on juice. Had it been left un-run for a while? Try key thing, try giving it a good run out. Good luck!

[Futuramic]

I drive the car every day, which is why it is surprising. I know the battery charges as it would have gone flat a long time ago. Perhaps it is just weak?

[mwcr85]

I had something similar on a Clio when an earth strap had broke. Check yours aren't loose or corroded.

[Fish981]

Sounds like not enough battery juice is getting to the car electrical system. Now this could be 'cos your battery is low on juice or you could have a high resistance in the starter circuit.

[Ray Luxury-Yacht]

I'd also add a to the dodgy battery syndrome.

I've seen weak batteries cause similar symptoms on cars. Porsches seem to be especially sensitive to it - the owner often doesn't believe it because they say 'it always starts first time and the battery's never gone flat'.

But a battery can have enough to fire the car up seemingly ok but after the start has drawn the reserve current, then be a little weak. The nominal voltage potential on a good battery is somewhere around 12.6 - 12.7 volts, but it only needs to drop to around 12.2 - 12.3 to cause some weird issues with the car. You can only really test for this with a multimeter - anecdotal assumptions based on how the car starts are not good enough.

Do a voltage test. Test the battery (without the engine running) then apply a load for five minutes - headlights on will do. Then switch the headlights off, and wait a few minutes for the voltage to stabilise. Then test again. Anything below 12.3 volts is not good news. (I bet a new battery in that case would sort your symptoms.)

Then while you're there, might as well test the alternator too. Start the car and test again - you need to see between 13.8 and 14.5 volts to be sure the alternator is charging properly.

[Roadrunner23]

My Jag S Type used to do weird things when the battery was on its way out so more than likely a duff battery.

[*Al*]

Poor earthing, either at the battery or an earthing strap.

[Fastdruid]

Or just dodgy battery connection. Fixed by removing it and replacing it!

[Ozzie Osmond]

1. Check battery. Unless it's new I always feel it's worth buying a new one as soon as you get a fail-to-start or crazy electronics. A knackered battery may be low on voltage due to a failed cell (which will send your electronics crazy) while still being able to deliver enough current to turn the starter.

2. Check earths.