ECM Malfunction

Hello everyone,

After I swapped my l98TPi 1991 for a new 383 custom SBC and modified some parameters in the bin file accordingly I've noticed there is a problem with the ECM. Recently I wrote an S-AUJP v4 bin file but the same symptoms. I've been tuning the VE and spark advance and the car runs relatively well, a few minor adjustments are needed but that's a different story. The problems since I've swapped the engine are:

• Radiator Fans won't turn on (I have manual switches that ground the ECM wires to turn them on -manual switch turns them on) when requested by the processor (I see that in Tuner Pro),
• they don't turn on in case of a SYS error either (I had a bad EPROM that caused that, before the swap the ECM worked fine after replacing this same EPROM, so I don;t think this caused the failure; there were random SYS errors, initially I thought it was a bad connection of the pins)
• digital coolant temperature reading on HVAC does not go higher than 91C although in the Tuner Pro I see it rising and about 10C lower
• MPG on the dash is pegged at 2l/100km
• RPM vs idle speed seems to follow HVAC CTS information, basically it goes to set temp for 91C instead of a different RMP in relation to the TUNER PRO data.

Possible cause: The battery went dead while connected to the car, it read 0.9V when I checked it, so maybe the voltage stayed too much at a critical low voltage.
My plan was to buy a spare ECM and see how that works, but it hasn't arrived yet.
Has anyone gone through such problem?

If you do determine the ecm is bad I have 1227727 and 1227730 ecms wasn’t sure what ecm you were using.

it’s the 1227727 but already bought 1
the MPG and hvac temperature seem to work now but it still doesn’t turn on the fans.

Is TunerPro showing commanded on ?
is the fan switch flag correct for a c4 ?

yes, when it’s cold they fans are commanded off then I can seen in TPro when the ecm commands them on but nothing happens. I’m currently using s-aujp xdf but it did the same thing with the normal xdf and stock settings except for VE tables, spark, injectors flow and a few other parameters.

I've recently replaced the ECM and the new one is able to start both fans. So clearly if the relays were good and wiring was fine the only thing left was the ECM. Fair enough, one of the integrated circuits that are connected to the Fan pins has a smell of burned electronics, I suppose it's a MOSFET. Should be replaceable. The other things are ok, like the MPG was actualy ok, and the Coolant temperature on HVAC display has the same behaviour with the new ECM, I belive it's has some special code to it and maybe a hysteresis.