ECU problem

[DaveHMS]

Hi chaps, a question for the KZN130 sparkies.
No preheat. I have no glowplug warning light & the glowplug relay is not getting an energising voltage. Relay function is ok on bench test. 12V glowplug supply is reaching the relay plug. Does anyone have an ideas for checking the ECU, from what I've gathered using the 'Search' tab, the relay gets its energising voltage direct from the ECU - no fuses in circuit.
I haven't found any electrical drawings that help.
Many thanks
Cheers
Dave

[Paul1566]

If you get no engine or pre heat light i do believe from experience your 5v circuit in the ecu is fubar........

[surfenstein]

im afraid to say your ecu is fried,this happened on a truck that was in the workshop recently.

[DaveHMS]

Thanks chaps, I feared the ECU being AFU.
I'd had both bats disconnected for obvious reasons, for close on 2 hours by the time I'd put the electrics back together. When I came to move the truck, I turned the key & lo, the glowplug light had returned & guessing by the easy start so had the plugs.
So, is it possible that the ECU, when powered down for a while, then powered up again, does some kind of 'cold' re-boot? Some of the marine navigation kit I deal with can be made to do this to get rid of otherwise 'fatal' software errors.
I'll see if it's still behaving in the morning.

[gwh200]

Couldn't say for toyo ecu's, but particular GM ecu's tend to store codes, but then throw them out again randomly, unless you clear them with an obd reader. The one I can think of, stored a throttle actuator motor fault and wouldn't allow the vehicle to start in anything except safe mode( no throttle). I couldn't clear the codes as my reader hadn't arrived. I disconnected the internal bats for 8 hours. When it went back together all was well. Along the same lines, there was a thread about disconnecting your +ve battery lead, and leaving headlamps on overnight. This gave the ecu somewhere for it's internal capacitance to drain down. Some reported a huge improvement in engine performance, as the original timing setpoints had been restored,. Perhaps it is possible, certainly sounds so.( I can't think why your 5v circuit would stop working then start again).

[DaveHMS]

Thanks Graham. I'm an ECU virgin, not even had one off, so to speak, so forgive potentially stoopid questions.
Are ECUs serviceable. Do the units have lithium back-up cells in them?

[Albannach]

They are servicable, they don't have backup batteries, they do store codes.

[Albannach]

( I can't think why your 5v circuit would stop working then start again).

Heat? Dislodging a joint somewhere?

[DaveHMS]

Non volatile memory? The ECU that is, not me. My memory is shot.
Thankyou gentlemen, as ever this forum is an invaluable resource!

[gwh200]

Heat? Dislodging a joint somewhere?

Dry joints definitely. I'm erring on the side of ECU confusion though. They dont have a battery but can store codes.
It seems they may require the main 12v battery to maintain this though.
Where's the goddam electronic geeks when you need them

APACHE !!!!!!!

[Paul1566]

Hasn't apache still got an ecu in bits on his bench....
He was investigating the spate of suicidal ecu's.

They have been known to just die.....
Could be yours is just dry joint or as you said leaving the batteries off caused the ecu to reset. If so what caused it to shut down.....

When mine went there was no engine check light on so it would not flash the stored codes that tell you the problem anyway... think if i remember right the 5v circuit runs that part of the ecu, so no 5v, no codes to check, or store......

If it is dry joint and not fixed you could be out and about and all of a sudden find the ecu shuts down on you, so be prepared..... join the AA

[Apache]

I have yes.

What makes it difficult is Toyota, in their wisdom (and good marketing sense) have chosen to use unmarked components in some areas, so its nigh on impossible to work out what they are - particularly without a circuit diagram. I think I'd have to start with a working one, and do comparative measurements.

Worth looking for dry joints as others have said. Usually recognisable by being grey rather than silver and shiny, but will do no harm to run an iron over all that look suspect. It's easy to get in. Pay particular attention to the parts that bolt to the case. I suspect some of those are the regulators, though some are probably gearbox solenoid drivers in a combined ECU.

Here's a thought, see if yours have any markings / identification on them and make a note for me?

[DaveHMS]

For now, I'm working on the assumption that the unit has re-set itself, prepared for that fact that my assumption may well be wrong.
Andy, if I do need to put it on the slab, I will let you know if there are any component ID's to be seen.
My brother is a pretty hot electronics design/development engineer who also writes code for much of the stuff he develops. If anyone has a busted ECU that they would like to donate for the general Surfers cause, I can get him to dissect it & see if he can glean some more detailed insight into the things & their repairablity.
Anyone know if the manual & auto transmission versions are different, or is it all in the proggies.
Cheers
Dave

[BUSHWHACKER]

Yes, they are different.