DF140a Blown ECU??

[Greg Moore]

Scenario, running 3/4 throttle on a 110hr 2013 140 and it flutter briefly and shut down. No beep etc. Try to restart and nothing, no beeps, gauges etc, not able to trim from side of motor. All other electricals on boat working fine.

Pull it out and find the 30A ecu fuse blown and strong burned electronics smell. Replace the fuse, within a couple of seconds ECO gets very hot in one spot and pops the fuse again. Pulled all things driven by the ECU, coils, IAC, injectors and fuel pump. Does the same thing.

Verified the 2 relays, trim relay and motor etc. Extremely expensive part when you don't know why it fried..

Any ideas? (note, 2013 is _not_ a 'white wire" motor)

Thanks!

[Hoosmatroos]

Sounds like your ECU is faulty. Is an expensive part indeed.

[Greg Moore]

Just in case anyone finds this in a search, it has been resolved.. The IAC valve went short circuit. Supposed to be 8-12 ohms, it's 0.2ohms. The stupid ECU on these motors doesn't monitor overload conditions on any of its driven outputs (IAC, ign coils, injectors, starter relay and trim relay)..

It does however drive this circuit at all times when running so a S/C in the IAC causes an overheat in the ECU until it destroys itself.. If it were a coil or injector gone S/C you'd notice something major and probably stop to check but this is only noticble at idle so when running for an hour like we were, you'd never now it wasn't working.

It will now be wired with a 2A fuse on the IAC circuit so if it ever shorts again it will blow the 2A fuse before it melts down the ECU..

Total penalty for this exercise is $2540 cdn for just 3 parts, IAC, gasket and ECU.

[Hoosmatroos]

Very good catch! I thought you said that the burning smell was from the ECU?

And indeed good to use a fuse.

[redlowrey]

Very good catch! I thought you said that the burning smell was from the ECU?

And indeed good to use a fuse.

''''' The reason the ecu fried, when you turn the key on, the main relay will be energized and battery voltage will power up the ecu, injectors, coils, iac, fuel pump, and so on, all these devices are ground side switched, meaning the ecu will apply the ground.

With the iac having a short in the windings, having little resistance, instead of pulling around one amp or more it will pull current till it fries the driver in the ecu and open circuits, or blows the fuse. He should have taken the ecu to an automotive computer repairer for a fraction of the price.

[dlnw98]

Did you not have the six-year Suzuki extended warranty for this?

[Lunchmoney]

I've got an ecu off an 03 I'll sell you cheap.

[dlnw98]

2013 should be a DF140a. If so, a different ECU than a straight DF140...

[Greg Moore]

dlnw98, I correctly called it a DF140a and no, we're second owner and according to the Suzuki rep the original owner elected to not pay the $100 to upgrade to 6yrs which sucked!

Lunchmoney, thanks but has to be from 2013, new one already on and running fine now.

Hoosmatroos, the burning smell was indeed the ECU, this was the first longer trip and I expect while the shorter trips got the ECU hot, it didn't reach melt down until we went for the longer trip.. The IAC was certainly shorted and with the ECU trying to run it it eventually heated the ECU to the point where it internally shorted and went totally.

This to me is a design fault of Suzuki.. I'm quite adept at automotive computers and they will (almost) all have a fault monitor. If you short or open a driven component it will throw a light and code (IE open or shorted IAC) and not fry itself continually trying to power the part. Suzuki doesn't have this function built in. The driven components are IAC, injectors, coils, fuel pump (plus started and trim relays but only on demand). If any but the IAC went S/C you'd know right away something major went wrong, not so much the IAC!

[JohnnyE]

Hi

I want to put a fuse into the IAC valve wiring. Which color wire is the correct one to put the in-line fuse into?

Thanks

Johnny

[Greg Moore]

Either wire is fine, it's not ground fed through the mechanical bolting to the engine. One wire is ground, other is 12v when being triggered. Both wires will see same load and cutting (fuse blown) either wire will drop all current draw going to it from the ECM..

One thing I found funny is the IAC is the exact same part found on some Suzuki cars such as Grand Vitara. Turns out the part from Suzuki Marine is a hair cheaper than from Rock Auto for a Grand Vitara.. Stupid price either way but have to thumbs up Suzuki Marine for not taking advantage of that word "Marine" and charging twice as much as the same car part.

[redlowrey]

Mate the iac valve does not work like that, it is supplied battery voltage via the main relay and the ground side which is inside the ecu is duty cycled, depending on the amount of air bypass required.
The df140 is based on the Suzuki vitara engine, that is why a lot of the components are the same as the automotive engine.

[Hoosmatroos]

The df140 is based on the Suzuki vitara engine, that is why a lot of the components are the same as the automotive engine.

That is interesting. Are any of the other engines based on a car engine as well?

[Greg Moore]

Redlowrey, it is in fact a shorted IAC that melted the ECU, that much has been verified. Suzuki didn't include an over current sensing on the ECU's on these like cars have (which would have disabled powering the IAC and thrown a 'short or open IAC' code).

Cutting either wire will open the circuit to the IAC, it doesn't ground via chassis mount. If you open the circuit then it presents infinate ohms of load (read absolutely no load) to ECU. The IAC will draw about 1.15A of load during normal operation (based on standard ohms on IAC and 13.8V feed). When it goes short circuit all available current in the quad driver in the ECU for it will absorb all the current the ECU is capable of and heat itself to death. Stupid design.. A 3A fuse to the IAC will allow normal current flow to an IAC but pop under a solid short.

Chances of an IAC going solid internal short is beyond imagination, going open is far more typical. That said, a short cost me an additional $1850 so I don't plan on letting that present itself again.

[redlowrey]

I am not disputing the fact that the iac was shorted, indeed it was, that is what fried your ecu as I said on page one, the point I made was the iac doe's not work the way you described, it is ground side switched and duty cycled.

If you had of taken your ecu to an automotive computer repairer it, would have cost a fraction of the price of a new one to repair it.

I don't think that if the same problem occurred in a vitara it would have been alright, I know that heavy current drivers like ignition coils can be open circuited to protect the driver. You were unlucky very rare.