ECM Trouble

[aaaaamartin]

Hi everyone, newbie, first post to the forum.

 

there is very odd things going on with the car's electronics lately.

 

It's a Regal 1990 3.1MPFI 2-Door Limited using the underhood 1227727 ECM.

 

With ignition on, engine off the SES and Low Coolant light both show a nervous flicker.

They are supposed to be steady on, but they do flicker 5 out of 10 times, and sometimes the are both

of completely. Sometimes coolant light is off, ses light is on and #1 fan engages. (Limb home???)

 

Any ideas what this could be?

 

Thnaks in advance Martin

[RobertISaar]

that is certainly ECM related... could be the ECM itself or the MEMCAL going out, hard to tell without swapping stuff.

[aaaaamartin]

Hi,

 

the ECM and the MemCal is stamped "AUMK".

 

Where can I get the memcal from?

Do I have to take care of the AUMK, when ordering a new ECM from rockauto?

 

Have hooked up a scope to some of the ECM lines.

Bat Fedd and Ignition is stable.

Hoocked up to LowCoolant and SES i see a square wave of 10Hz.

I found out, that opening the throttle triggers the malfunction. closing it, makes it go away.

TPS is ok, and tapping the ECM has an impact on the error.

So I guess the ECM / MemCal is faulty.

 

All chips inside are crypted, so no way thinking of repair. Will resolder here and there but order new Ecm / MemCal at the same time.

Will also check the all coils and sensors again, just in case, to make the new part feel comfartoble with it sorrounding.

 

Martin

[Garrett Powered]

some times you can just pull the ecm fuse by the aux post and just do a idle re-learn. I had to do that the other day. It was real wet and cold and my serpentine belt is all dry and old, had something to do with it. and looks like the spring is getting weak. I was like damn, car's acting weird. Idle was waving up and down.

[RobertISaar]

hmm..... i don't have the binary for AUMK in my archive, but that is at least correct for a 1990 3.1 W-body. part number for it is 16151238, if you could find one.

 

for 1990, there are 6 main "series" of MEMCALs for a 3.1 w-body:

 

manual

AMYR->ATMM->AUBL

(california)AMYP->ATML->AUBK

 

3-speed auto

ANAS->ATSL->AUBM->BBXX->BFBK

(california)ANAT->ATSM->AUBN->BBXY->BFBL

 

4-speed auto->

AMYK->ATFF->ATSN->AUMX->BBXZ->BFBM

(califonia)AMYL->ATFH->ATSP->AUMY->BBYA->BFBN

 

then there are a couple of them that I can't identify why exactly they exist.

 

 

ARCW (4 speed)

ARCY (3 speed)

ARZX ???

ATLM (export 4 speed)

AUMK ???

 

yours happens to be one of them.... is there anything peculiar about your car?

[aaaaamartin]

peculiar? I love the car and besides that, I'm from Germany, and it's an export Regal.

They did some conversion on export model. that is the head-lights and battery wires. Also rear lights are wired differently for brake and turn signalling.

Ever seen a regal with high low beam headlights like that? To me it looks so much better than the original ones.

 

Thats why it might not be in your list. Anyway, the Chip AUMK thing is all greek to me.

I need to order spares so I'm in doubt, does one if these fit?

 

http://www.rockauto.com/catalog/x,carcode,1021093,parttype,2896

 

 

Thanks

 

Edited November 24, 2014 by aaaaamartin

[aaaaamartin]

I was just looking at a Tunerpro definition, your the author of right?

I was just downloading it yesterday, but will try it out tomorrow. Have to solder a max232 conversion first, and grab an

old laptop with hardware rs232 from the office tomorrow. Have scoped the M-Line this afternoon, and there is data.

Don't know much about ALDL and ECM sniffing, but I'm software engineer what should make thins a liitle more easy to grasp for me.

 

Any chance tunerpro will work with the diy interface and my ecm?

I'ts 2 o'clock in the morning and i have to go to work tomorrow.

 

ttyl Martin

Edited November 24, 2014 by aaaaamartin

[RobertISaar]

ECMs are interchangeable, so any with the correct part number(1227727 or equivalent) will work.

 

being an export car would certainly count as peculiar... I don't know what all would be different in the calibration because of it. I've seen some middle-eastern export calibrations and there wasn't a significant difference other than changes for the fuel they were running at the time.

 

tunerpro will work as long as you have the correct ADS/ADX(and if the cable doesn't have issues. I've built MAX232 versions before with no problem, but the "2 transistor" schematic has never worked for me). I assume(which has gotten me into trouble before) that the 90 exports used the same base code as the 90 domestic cars, in which case you'll need the $88 definition. if it is built using the 89 software, then you'll need the $6D definition.

[aaaaamartin]

Hi,

 

replacing the ecm fixed it. Bought a remanufactured one.

ECM's up to 1994 are said to fail due to swell of pcb coating used back then.

Remanufactured item has the old coating removed and a different one applied to it, I could easlily tell from looking at the pcb.

 

Have also replaced the TPS, DIS, Spark Plugs and Wires.

Code 42, was the dying message.

 

Have not yet had the time to checkout the TunerPro interfacing, but definitely will.

Any chance I can set IAC-counts with it?

 

 

Thanks for helping out, Martin!

Edited December 1, 2014 by aaaaamartin

[RobertISaar]

setting IAC counts? maybe, it depends on what exactly you're referring to. i'll have to dig into my documentation for the 90 calibrations, but I'm fairly certain it supports being able to force the IAC Minimum to whatever you desire it to be. the ECM will eventually learn it on its own and will adapt after the IAC minimum is forced to be changed as well to keep within the target idle speed's acceptable range of error.

[aaaaamartin]

Hm, what will a tech-1 do when performing idle learn? Besides I don't have a tech-1, I was learning the car with operating temperature reached, ecm reset, idle in drive 10min, off, on, 5min idle in drive.

But that was years ago, not long after I bought the car. I will not do it that way again. The adaptive learning is taking too many rides, and I think it is very dangerous. The car is very likely to stall while in traffic!

There is plenty of voodoo roumors spread in forums concerning the idle learn. Just looking for a way to do it, that doesn't suck the transaxle.

 

Nevertheless I'd be better off cleaning up the throttle body before anything. I think this will cure the symptoms with unlearned idle.

[RobertISaar]

I don't have a tech1 to monitor/confirm, though I do know someone who was significantly involved in their development, but IIRC.... when a tech1 does an idle learn procedure, it doesn't modify anything, it just monitors where the IAC is positioned while idling and when it reaches a target coolant temperature and no unusual loads are being placed on the engine, it takes the IAC position it is seeing and sends a command to the ECM to update the IAC Minimum value to that position.

 

from what I remember with a stock calibration(haven't run one of those since 2009), the IAC Minimum position that is used as a default value when power is lost to the ECM, the IAC minimum is set far too low, something like 10 steps. I haven't seen too many engines that like to idle with that few of steps, they eventually learn their way up to the 20-25 range after a few run cycles. if you're able to run a custom calibration, once you figure out where your engine likes to idle, you can change the default value to that position so that should power to the ECM be lost again, it won't take long to get it to idle properly.

 

cleaning the throttlebody and the IAC/IAC passage itself can certainly help.

[Garrett Powered]

If it stalls in traffic, there is no way to just clean it and expect it to work. There is a table that needs a custom calibration and burn a new chip.

[Garrett Powered]

That is in reference to the voodoo rumors that are spread on forums, most of which are replacing and swapping out parts. anything but actually adjust the calibration. It is a very safe easy change in the software, something you would enjoy doing for sure.