Comparing ECU’s (96 850 vs 98 V70)

[SonicAdventure]

Hi everyone, I’m a little confused about the ECMs in these two cars. Photos attached.

The 98 has Bosch 261-204-299 and the 96 has 261-203-077. Interestingly the 96’s has the word “update 810” under the part number and then someone hand wrote “346, 12/97” on another part of the label.

According to the VIN comparison site provided by another user a few weeks ago, both of these base model engines “with air pump” should be running Motronic 4.4

Can anyone explain the difference between these two units and are they interchangeable? I’m parting out the 98 and I’m taking both the ECU and the transmission module, but just trying to understand what is going on here. Thanks.

[Chuck W]

So, I can't give you any definite info but the '96 NA ECU is M4.4.

One thing that may be an issue is control of the AC.

The TL;DR version is that while both the ECUs are M4.4, the AC routines are different due to the different ECC modules between the 850 and V70's. You may wind up with non-working AC in the '98 if you try and use the '96 ECU in it.

My familiarity comes from dealing with the wife's '97GLT, which is the only turbo 850 (in the US) that used the M4.4.

[jimmy57]

Turbo 96 is Motronic 4.3, not 4.4. 97 850 GLT with the low pressure turbo engine was the first turbo 4.4 with the 98 high pressure turbo versions getting 4.4 in 1998. My recollection is that 4.3 in a 4.4 car gives an air conditioner issue as the pressure cycling switch on low side line is a signal switch on 4.4 but is in the compressor clutch power supply circuit on 4.3. Some 4.3 have EGR so you end up with EGR circuit issues also. 4.4 uses electric air pump and will have codes for open circuit for the vacuum solenoid and the pump relay and will fail the secondary air system test when used in 4.3 wired vehicles.

[greg850r]

This seemed like a good place to ask this question; Is there a knowledge base somewhere that I can learn about ECUs in these cars? I have a 97R sedan someone put a 5 speed in and I'm trying to sort out driveability issues. There is no TCU currently in it at all. Here's a pic of the ECU.

97R_ECM.jpg (67.67 KiB) Viewed 2755 times

Also, I have a 96 GLT 5 speed N/A sedan. I could open the box and post a pic of the ones in it if it will help you.

[erikv11]

Yes, both of those are m4.4. I also don't know what the "update" . means.

OP didn't ask about the swap in this direction but it is important to clarify: Actually, using the 96 ECU in the 98 could be catastrophic, it shouldn't be done, it can be much worse than no AC if they are incompatible. An ECU for the 4.3 (or "older") wiring setup when put into 98, then the AC compressor does not turn off, and overheats, and is ruined. The 97 GLT is somewhere in between and it is not clear what is going on with the AC there.

On the other hand, the 98 ECU in the 96 (or a 97, for that matter) should be fine to test - the AC will either work normally, or not at all.

[erikv11]

Turbo 96 is Motronic 4.3, not 4.4. 97 850 GLT with the low pressure turbo engine was the first turbo 4.4 with the 98 high pressure turbo versions getting 4.4 in 1998. My recollection is that 4.3 in a 4.4 car gives an air conditioner issue as the pressure cycling switch on low side line is a signal switch on 4.4 but is in the compressor clutch power supply circuit on 4.3. Some 4.3 have EGR so you end up with EGR circuit issues also. 4.4 uses electric air pump and will have codes for open circuit for the vacuum solenoid and the pump relay and will fail the secondary air system test when used in 4.3 wired vehicles.

These are both NA ECUs, no turbo here. This 96 NA with air pump has a Motronic 4.4 ECU. Both are 4.4.

[SonicAdventure]

Ok so just a couple of follow up questions related to my original pictures:

The consensus is that even though the part numbers are different they are both 4.4 systems. How can you tell? What is the deciding factor to determine this?

The 98 is the one going to the junkyard, the 96 is the keeper. I’m keeping the ECU and the trans computer from the 98 regardless, but trying to determine that if I really ever needed to use either ECU or trans modules from the 98 in the 96 that I would generally be Ok. Is that a reasonable assumption?

[Chuck W]

Ok so just a couple of follow up questions related to my original pictures:

The consensus is that even though the part numbers are different they are both 4.4 systems. How can you tell? What is the deciding factor to determine this?

The 98 is the one going to the junkyard, the 96 is the keeper. I’m keeping the ECU and the trans computer from the 98 regardless, but trying to determine that if I really ever needed to use either ECU or trans modules from the 98 in the 96 that I would generally be Ok. Is that a reasonable assumption?

As mentioned, the '96NA with the secondary air pump is M4.4.

The '98 ECU may work in the '96, but you will most likely not have functioning AC, just like what I ran into on the '97GLT.

I have no info on the TCM.

[erikv11]

What Chuck said ...

... The consensus is that even though the part numbers are different they are both 4.4 systems. How can you tell? What is the deciding factor to determine this?...

All P80 cars with air pumps run Motronic 4.4
All 1998 P80 cars run Motronic 4.4

... The 98 is the one going to the junkyard, the 96 is the keeper. I’m keeping the ECU and the trans computer from the 98 regardless, but trying to determine that if I really ever needed to use either ECU or trans modules from the 98 in the 96 that I would generally be Ok. Is that a reasonable assumption?

Yes, reasonable. Keep in mind it is extremely rare to need to swap either ECU or TCU, they basically never go bad. But i'd probably keep them too.

Also I would keep the brake caliper slide pins if the calipers are factory. Those are stainless steel, whereas basically all rebuilds these days use some kind of pot metal slide pin, that corrodes quickly and therefore may seize the caliper.

[abscate]

MVS just got 1,000,000 hits for people trying to compare shades of brown, btw.