Fried ECU

[roytarolla]

I have a 4AGE ke70 running a standard loom with a few minor modifications lengthed wire here and there etc.

Any way I got a flat battery so attempted to jump start it but battery was to flat and wouldnt crank fast enough to start. I then connected a charged battery and attempted to start and car filled with smoke.

pulling back the carpet revealed that wire that supplys the main "ON" power to the ecu had fried and on inspection of the ECU i found a diode had blown apart. The rest of the loom is fine. Terminals on battery were all corect way round etc

Has anyone experienced this before? Its easy to fix but i just want to prevent it happening again.

[Asphaltcowboy]

sounds like someones powered your ecu directly from the battery unfused, your probly gona want to replaced ne fired wiring and put a fuse link on the postive batt feed, we see stuff like this every day ae,lucky ur wiring didnt catch on fire cos then it gets messy lol having things unfused of a battery is a big no no not worth frying a whole loom for the want of a 5 dolla fuse link

[RunningRich]

Sounds like you jumped it with the leads backwards.

AA did this to a friend's father's Sylvia once with similar results. Winners.

[MAGN1T]

Sounds like you jumped it with the leads backwards.

AA did this to a friend's father's Sylvia once with similar results. Winners.

The diode is there for reverse protection.


It's done it's job....easy fixed.

Steve

[sergei]

If it was crossed the polarity, the diode would not blown (I assume it is in series, as in not clamping). The diode would blow if the current that going through it would exceed it's rating, this possible if the ECU would draw too much current (injector driving transistor connected to +12V, or other drives shorted to +12V) or over voltage (faulty regulator on alternator).

[DeeCee]

yeah.. mate did it in his suby with a microtech. Tried to jump start the car and it fried something in the ECU.

[ChaosAD]

The 4age ecu's have a large diode between +B/+B1 and E1.

+b and +b1 are connected to the battery all the time, even if the key is off.

Should the battery get connected in reverse, the diode will provide a low impedance path between +b/+b1 and e1, more than enough to blow the ecu fuse (if there is one). Otherwise your loom etc will act as the fuse lol.

[sergei]

The 4age ecu's have a large diode between +B/+B1 and E1.

+b and +b1 are connected to the battery all the time, even if the key is off.

Should the battery get connected in reverse, the diode will provide a low impedance path between +b/+b1 and e1, more than enough to blow the ecu fuse (if there is one). Otherwise your loom etc will act as the fuse lol.

Oh I see, never bothered to check it which way it is. So in this case definitely reverse polarity with no fuse will cause this as the diode seems to be able to handle tens of amp of peak current.

[RomanV]

The pin from the plug end to the circuit board burns out before the diode blows.

[NZ_AE86]

Reverse jumped, fuse may not have saved you, sometimes the ecu can be repaired but not always. You should check your Alt main fuse too and if you don't have one then you may have killed you Alt too.

[roytarolla]

Finally got around to fixing the car. Looks like a random spike has caused diode to blow. I am sure leads were not around the wrong way. The only protection was a 60A fusalbe link, as fuse box had been removed and bypassed, which wouldnt save the 30A diode. So I have added some fuses, replaced burnt out wire and blown diode in ecu and now runs mint again. Cheers for the help.