Code E041 and ECM Replacement

[MarkV]

Well here we are again! I recently had the cam magnet and the crank sensor replaced, the coil and ignition module are also new (with different ones since my last post), the wires are tight and fine, and guess what?! E041! After several days of driving e041 pops up again with a momentary loss in power. So, I think it is a bad ecm. How do I replace the ecm? Where is it located and what are the removal procedures?

[KDirk]

Wes,

ECM is located up behind the glove box and is accessible by removing the trim-out panel under the dash on the passenger side. Some contortion is needed to get to it and remove it, but it is not impossible unless you have back problems or are built like a line backer. Once the lower trim panel is removed (held by screws under dash, and wing nuts at fire wall) you can look up in behind the glove box and see a silver (aluminum) rectangular module with three large harnesses going into it. This is the ECM. Think there is one nut to remove to release the mounting bracket and then it pulls down and out.

Be forewarned it is a tight squeeze, and be careful releasing the three large plastic connectors. You may also get hung up on the floor carpet at the edge of the passenger footwell, but with some finesse it can usually be pulled out. You'll need to remove the MEM-CAL (chip carrier module) inside the existing ECM and swap it into the replacement unit. There is a service cover held on by two screws that covers the MEM-CAL. It is a long thin plastic module, light blue on top and brown on the bottom. There is a small circular window on the top through which the MEM-CAL calibration code can be viewed (a 4 digit code, usually all letters)printed in black on a silver sticker.

The mem-cal is released with two small thumb latches on either end of the socket. Be careful not to break these on removal or installation as they hold it in tightly and without one or both vibration can cause the chip to work loose.

Reinstall of the ECM is opposite of removal, and will be fairly clear once you have removed the old one.

KDirk

[Machiner 55]

John F.

[padgett]

If the SES light comes on for a code 41 and goes off it is an electrical issue & could be a connector (including bulkhead). If the magnet falls off, the warning comes on as soon as the engine starts and stays on.

ANBM is an original PROM for the 88, ANCX is the revised one. Major correction was inaccurate MPG readings.

[SeanR]

If the SES light comes on for a code 41 and goes off it is an electrical issue & could be a connector (including bulkhead). If the magnet falls off, the warning comes on as soon as the engine starts and stays on.

ANBM is an original PROM for the 88, ANCX is the revised one. Major correction was inaccurate MPG readings.

Is there a quick way from CRT to determine which module is installed? How would one install the new ANCX type?

[D-a-n-i-e-l]

Is there a quick way from CRT to determine which module is installed? How would one install the new ANCX type?

Not to high jack this thread, but that means that the MPG is calculated in the ECM? This means there is hope for fixing my MPG reading.

[Guest Mc_Reatta]

Wes, refresh our memories, did you replace both the cam magnet and sensor, or just the magnet? Someone recently posted photos of a damaged sensor back (done by failing magnet) but I don't remember if it was you or not.

Could always be a problem with the wires between the sensor, ICM, and ECM, but not easy to check without DVM and some tricks or better yet an O'scope.

If you do go after the ECM, if you have problems hanging like a bat under the dash, you can remove the glovebox and get another angle to look at things and get access to the upper mounting arrangement, but does need to come out the bottom.

Also every time I play with an ECM, I end up knocking the vacuum line to the HVAC controller sitting next to it loose. After you get the ECM back in place, check the vacuum lines going to the HVAC to ensure they're attached well before you seal things back up or you'll be defrost mode only.

[Guest Mc_Reatta]

I'm sensing an ambush taking place here! :cool:

Thought on of the major changes from the 88 PROMS to the 89 PROMS was how the VSS signal was converted to MPH and displayed by the IPC. In one the ECM took the lead, and in the other the BCM took the lead.

Also I though the calculation of the MPG was modified in the BCM programming during 88 to make it more accurate.

So Daniel, I think your hopes are still just hopes unless my memory is off. Why don't you start a new thread with what your using for ECM, BCM, and reprogramming done, and we'll kick it around here for awhile.

[MarkV]

Wes, refresh our memories, did you replace both the cam magnet and sensor, or just the magnet? Someone recently posted photos of a damaged sensor back (done by failing magnet) but I don't remember if it was you or not.

Could always be a problem with the wires between the sensor, ICM, and ECM, but not easy to check without DVM and some tricks or better yet an O'scope.

If you do go after the ECM, if you have problems hanging like a bat under the dash, you can remove the glovebox and get another angle to look at things and get access to the upper mounting arrangement, but does need to come out the bottom.

Also every time I play with an ECM, I end up knocking the vacuum line to the HVAC controller sitting next to it loose. After you get the ECM back in place, check the vacuum lines going to the HVAC to ensure they're attached well before you seal things back up or you'll be defrost mode only.

No, that was not me. We replaced both the magnet and the crank sensor (which was giving us starting problems I would have to crank it a few times to get it going). The car starts fine now, so, it fixed one problem. We replaced the fuel pump and 2 relays which also helped the engine prime (there was a short in the old pump) and the transmission was a problem coming down the road. My new coils and ignition module were replaced with different ones from Standard Ig. Company. All connectors on the engine side are tight I will check under the dash today with the connectors to the ecm. But, I already ordered a new one and would rather replace it. I have a feeling that this intermittent problem is being caused by a computer failure. It smells of computer issues with the old box as the problem is very predictable and not constant it is almost like the computer goes through certain cycles. Thereby not communicating correctly and causing these running problems.

[padgett]

I don't guarentee anything from memory any more but might look here for an ANCX discussion. There was also a TSB for 89s and 90s but that was mainly about cold starting. The four digit numeric code for PROMs are at ED99. ANCX will report 3534.

[Guest Mc_Reatta]

It was crazytrain2. Here's his photo of the cam sensor, which was the victim of a murder suicide by the cam magnet.

I would hope you did a visual inspection of yours before reinserting. Normally these sensors are bulletproof, but can go bad.

If you have a spare ECM, I'd encourage you to swap it out to see if it cures the problem. But if you have to buy a new one, you might want to do some checking first to see if the problem is somewhere else before spending your money.

[Guest Mc_Reatta]

I don't guarentee anything from memory any more but might look here for an ANCX discussion. There was also a TSB for 89s and 90s but that was mainly about cold starting. The four digit numeric code for PROMs are at ED99. ANCX will report 3534.

Well, I checked up on my memory and found somebody named Padgett posted back in 2006:

OK, a bit more info: the 88s has a TSB for low MPG readings compared to the actual use and a reprogrammed PROM code ANCX p/n 16123488 was issued by GM per TSB 88-6E-23. The MPG is 15-20% highter with the new Memcal. I believe that is to only Memcal now available for a 1988 Federal Reatta. With the ANCX ED99 will show a PROM ID of 9864.

Unfortunately, I can't find a free copy of that TSB anywhere. Reatta.net doesn't list it in the docs section that I could find.

But now I think that it was an ECM PROM and not a BCM PROM. So if someone could decipher the changes in this PROM change, maybe Daniel could fix his MPG readout.

[padgett]

I have no idea where the 9864 came from.

Does this help:

Edited May 20, 2013 by padgett (see edit history)

[KDirk]

Regarding the topic of ECM PROMS:

ANCX is the revised/corrected ECM PROM for 88 federal emissions. I do not think there was a California specific version, but could be wrong about that. Have never seen reference to one in any case. No revised BCM or CRTC PROMS were ever issued as far as I can determine, and if they were it would have required an exchange of the entire module as the PROMS in both the BCM and CRTC are soldered in place.

If you pull the ECM and take off the service cover over the MEM-CAL, the letter code on the PROM inside the MEM-CAL is visible through an opening in the light blue carrier cover. You can get the numeric service code (but not the letter code) through OBD, parameter ED99 as already posted.

Big problem is that if you need one now, they are no longer available new from GM. A MEM-CAL has to be modified with a newly-burned PROM containing the ANCX ROM image. This is not a pleasant procedure as the PROM is soldered into the MEM-CAL carrier and is very difficult to remove without damage. A new PROM then needs to be installed. I put in a low profile machined pin socket (with the pins cut a bit short) and soldered that in place onto the carrier contacts. Then put my newly burned EEPROM (did not use the UV erasable variety) in the socket and snapped the blue cover back on. It has worked fine ever since, so this is what I would recommend if you really need an ANCX prom in your 88.

KDirk

Edited May 20, 2013 by KDirk (see edit history)

[padgett]

Just to expand a little, a decade ago, erasing/reprogramming a factory MemCal (27C256 UV Prom) was quick and easy. In the decade since the Proms have aged and the last time I tried, could only get a good burn on about one in three.

I do have an assortment of new PROMs and MemCals but as mentioned it is not a trivial task without a specific (ex$pen$ive) desoldering station. What I have to do is to cut each pin (28), use a low power (5w) iron to remove each pin, clean the individual holes, insert the new 27C256 (or equivalent), resolder tabling care not to damage the resisitor network that is the other half or the MemCal, then burn the new program. The entire process takes about two hours and I just do not have the spare time.

[Guest Mc_Reatta]

It's probably a moot point now, but if someone had an original 88 PROM and the newer ANCX version and dumped the contents, maybe a understanding of how the MPG values are calculated could be found. That might give Daniel and others who have modded their engines the ability to modify those calculations so their MPG readouts would be more accurate.

[padgett]

Did that in 2001

Comparing files ANCX.DAT and anbm.dat

00001502: 31 23

0000157F: CA BC

0000158C: 42 34

000015DB: ED DF

000015E1: 9A 8C

[Guest Mc_Reatta]

1948Lincoln, don''t mind us, were just chatting amongst ourselves waiting to hear how your ECM change went.

Has an engine tuner figured out what those changes entailed? Don't seem to be enough to be changes to mapped table values, so may be just values in a formula, or changes to the formula operations.

[padgett]

The GM Prom is contains both maps and program, the maps/constants are all in the first 1000h and the second 1000h is all program so the code change (15xxh) is in a calculation. You just asked what the change was but at one point I sent out a CD to several people with all known 5B .bins, disassemblies of ecm and both proms in bcm, plus a commented disassembly of the the ECM (needed to reprogram quite a bit of the codes to keep Greg's manual transmission from triggering many errors).

That was back when I could reliably reprogram PROMs and had some spare time.

[MarkV]

Hmm, I have no idea what is going on here! Computer stuff is way above me though I am only 24! Replacement is what I do know! It looks like it will be a couple of days until I receive the computer. It is the only thing left as everything else has been replaced. The rate of the loss of power is almost predictable and it takes a couple of days for it to do it again after I unplug the battery....

[KDirk]

I kind of wonder if the MPG calculation error actually was in the CRTC ROM, but since it is easier to update an ECM PROM (MEM-CAL is socketed and meant to be serviceable, CRTC ROMS are not) they did a back-door fix by tweaking the data the CRTC sees from the ECM. I do know the letter codes are different on 1988 vs. 1989 CRTC PROMS. I am unaware of any detectable changes operationally from 88 to 89 in the CRT, so this may be an explanation for revised firmware in the CRTC in 1989. An interesting theory anyway.

KDirk

Edit:

Wes, I would add that if you are getting a "reman" ECM, it is a crap shoot as to whether or not it will be good. I had very bad luck with rebuilt ECM's on my 88, took 4 exchanges before I got one that was 100% right. Either they (re-manufacturers) do not test these very well before shipping out as "OK", or they are just incompetent. Just a forewarning in case you get some other unpredictable behavior that was not present with the one in the car now.

Edited May 21, 2013 by KDirk (see edit history)

[Machiner 55]

Wes,

I concur with DKirk. ("Dr. ... Do you concur?")

I've only changed out one ECM with a reman. unit once but I had to swap it out twice due to the fact that the first one wasn't working properly.

As KDirk said,

...some other unpredictable behavior that was not present with the one in the car now.

If I remember correctly, with the first replacement, I started getting error codes not present prior to installing said unit. Then, each time they were cleared, another couple of codes, some different from the previous, would appear. Took the first one back and exchanged it for another reman. and all was good again. Drove me nuts for a while though.

John F.

Edited May 22, 2013 by Machiner 55 (see edit history)

[MarkV]

Well lets just hope that does not happen! I bought mine through Rock Auto.

STANDARD MOTOR PRODUCTS Part # EM8253 {#1228253, 16198264, 88999198} Reman Reman; Number of Electrical Connectors: 4

OE No. 1228253, 16198264- $78

More Information for STANDARD MOTOR PRODUCTS EM8253

It apparently has a 1 year warranty. All of the others only had 30 days! I could not find a new module and I looked, looked and looked (with the exception of a $400 or more module).

On an unrelated issue, my IAC is going bad so I bought another one (stalled a couple of times when I took my foot off of the gas). I cleaned mine a couple of months ago and it held it together temporarily but the cleaning should not be considered a perm. fix. I was able to get another for $16. Had to get one for the Lesabre and went ahead and got one for my sister's Park Avenue (also a 1989).

[MarkV]

So, I put in the computer and the chip in the computer and the car runs like crapola! Does it go through a re-learning process?

[padgett]

Shouldn't, when I have installed reworked PROMs the car always runs smoothly on restart. I may run a little rich but gross learning is just a few minutes.