1G ECMLink loses program

[bh4000]

1g AWD with ECMLink. My ECMLink randomly reverts to some default state. I have completely rewired the car and disconnect the battery everytime I park it with a 150a circuit breaker.

I have verified there is always battery voltage at pin 103 for the battery backup input, regardless if the breaker is tripped or not.

Am I missing something? Does some other pin on the ECU need 12 volts for it to not lose its programming? Or is this a configuration problem in ECMLink?

 

[ist dwa]

That's not good, I would send in the ECU. The ECU should never lose it's tune even if the battery is disconnected.

 

[bh4000]

Yes, it sure is annoying, and dangerous...

 

[steve]

In your rewire did you retain the MPI relay? IIRC the DSMLink needs time after you turn the ignition off to do housekeeping before the power goes away.

Normally with an MPI relay there is a couple of second delay between you signaling the shutdown with the ignition switch and when the ECU turns off the power via the MPI relay.

 

[danl]

In your rewire did you retain the MPI relay? IIRC the DSMLink needs time after you turn the ignition off to do housekeeping before the power goes away.

Normally with an MPI relay there is a couple of second delay between you signaling the shutdown with the ignition switch and when the ECU turns off the power via the MPI relay.

Wow, that is great information. Does dsmlink require time even if no changes have been made? I sometimes disconnect battery power with key on/engine off when working on the car.

 

[Sirius1995]

Sounds like either blew capacitor or messed wiring to me, it should always have power to keep memory

 

[steve]

There is a difference between retaining the RAM data and whatever housekeeping is needed.

The unswitched power feed (1G pin 103, 2G pin 80) maintains the RAM and powers the circuit to process the ignition run input and turn the MPI on but doesn't provide power for CPU cycles after the MPI switches off.

Until we hear back from the OP we are just guessing.

 

[biglady112]

There is an audible click you will hear from the relay/ecu. It takes on average around 6 seconds after key off for this to happen. Make it a habit to wait to flip the cutoff switch until you hear this.

Steve is absolutely correct in making sure the mpi relay is in place. With that said, it doesn’t have to be the factory relay. I have done it with a regular 30/40 amp automotive relay on multiple 1g’s and 2g’s where I made a wiring harness from scratch for the stock ecu.

Steve, team NABR and the dsmlink guys helped me with this well over a decade ago. If you search the dsmlink forums you will find my thread documenting what has to be done for a 1G.

 

[steve]

Steve, team NABR and the dsmlink guys helped me with this well over a decade ago. If you search the dsmlink forums you will find my thread documenting what has to be done for a 1G.

After a decade or more my memory starts to get fuzzy enough that I start to include disclaimers on what I remember.

I can't say where I picked this up but it's just as likely I could have posted it on NABR as I heard it there. I know Tom mentioned that it was an issue but what version, when, and where we were discussing it no longer register. I'm only sure it came up while discussing building race car wiring harnesses and the need to maintain the delay between ignition off and power off that the MPI circuit provides.

 

[bh4000]

Sorry for the delay, I had to look over my schematics. This is a 100% rewired car, engine and chassis. I am using 30 amp mini relays, and the new wiring is exactly the same as factory mimicking the MPI function.

I think the problem I am having here is I am disconnecting the battery with the breaker before this ~6 second RAM cycle is completed.

I'll put a voltmeter on my version of the MPI relay to see if the ECU is keeping it energized once the motor stops running.

 

[biglady112]

I have never wired one to keep power to the ecu once the switch is cut off. Doing this I have never had an issue. I have never had a problem cutting the power for the backup.

 

[steve]

I don't expect most race cars need to retain their long term trims and such but as we had discussed DSMLink needs the shutdown delay to save it's state without corruption.

Does dsmlink require time even if no changes have been made? I sometimes disconnect battery power with key on/engine off when working on the car.

I haven't looked at the DSMLink code to see what the conditions are or what they are saving, so you would have to ask ECMTuning what happens if you just cut power versus cutting it after you have signaled a shutdown with the ignition.

 

[bh4000]

Mark this as solved. I verified that the ECU is keeping my generic MPI relay closed for about six seconds after I turn off the engine. I was disconnecting battery voltage with the 150 amp circuit breaker before this cycle completed.

Thank you for all the help!

 

[vanilla gorilla]

@bh4000 What version Link do you have? Ive had several cars with Link and the only one that would lose tune after voltage loss was on an old v1 setup. I just assumed it was a v1 thing? Can anyone confirm because now Im wondering.

 

[steve]

On a 2G version 1 and 2 both would loose their settings if the ECU lost backup power. With the introduction of the red EPROM replacements with V3 that stopped being the case.

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On a 1G there was always some non-volatile memory on the DSMLink board that plugged into the EPROM socket, so they didn't loose their settings.

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