Hi guys,

has anybody tried to repair 561 ECU by opening it and replacing / resoldering faulty components? Just like we do with our Fuel and OD relays.

I'm suffering from occasional no-start condition and want to exclude the ECU from the possible causes list.

Thanks,

IF

Is the year a typo or do you have the wrong ECU?? I thought '88 was the last year for the 544.
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Dave Shannon
Spring Valley, California
'65 1800S ????K
'67 1800s 79K
'73 1800ES 117K
'88-240 190K+
'92 745Ti 160K
my pages

Yep, it's rare, but I have LH2.4 w/ OBD box and 561 ECU on an '88 european car. But no Check Engine light on the instrument panel.

IF

Dave, I thought the same thing a week or so ago when this first came up. What we are hearing is LH2.4 made a debut in Europe, not here. First I'd heard of it.
--
Art Benstein near Baltimore Crrrrazy Ray's!

Ahhh, got caught by the old international differences, that's another I'll have to add to the file.
Thanks
--
Dave Shannon
Spring Valley, California
'65 1800S ????K
'67 1800s 79K
'73 1800ES 117K
'88-240 190K+
'92 745Ti 160K
my pages

'88 used the 554 but as we are learning, cars will run with a whole lot more ECUs than we suspected. Someone recently found an LH 2.4 ECU running a LH 2.2 car OK but maybe that is what you refer to. I myself have not found a 16 valve ECU that did not perform well in my LH 2.4 245. Anyway, back to the "Flying Flahood".

The connectors for the 2.2 and the 2.4 are not compatable? Dan

No, they are not. 2.2 uses a 25 pin plug and 2.4, 35.
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Art Benstein near Baltimore Crrrrazy Ray's!

Don't forget to check the ignition computer.

How are the 25 amp fuse, crank sensor, fuel pump relay? After those likely culprits, an ECU swap is the way to diagnose. Usually, the loss of ground is not intermittent as far as I know.

Check the junk yard's, I got a remanufactor 561 for $20.00
Thanks
Rodney

Thank you Robert for your reply.

Nice to hear that ECU failure would not be intermittent. Anyway there's a threat that it will fail someday, so you can call it preventive maintenance. If it's all about replacing some low-cost components (like transistors, capacitors, coils etc.) on a PCB, why not?

Regarding the fuel pump relay, the last time I resoldered it was yesterday, usually I tend to do it twice a year or so. Replacing the crank sensor would be my next action - all that keeps me from doing this job now is a nasty placement of the sensor behind the engine, I cannot even see it.

BTW, the previous owner was crazy enough to eliminate the 25-amp fuse and simply solder that connection together. What circuits should it protect, that are not protected by other fuses?

IF

You resolder the fuel pump relay twice a year??? Wow, that's pretty cautious and a bit of overkill, IMO. Normally it's a one-time deal to fix the factory screwup. You might even make things less reliable by causing a trace to lift. Why not just resolder a spare relay and keep that in the car?

25 amp fuse feeds the injectors, idle valve, computer and plus side of relays direct. No protection for those items if anything goes wrong.

When I first heard of the common failure of fuel pump ground output on these computers I figured it ought to be a simple problem solved by replacing the relay driver transistor, like it would be if this problem happened to the older LH2.0 and LH2.2 fuel computers.

But as others too have learned, the transistor that drives the fuel pump relay is part of a 40-pin ceramic custom hybrid circuit which makes up most of the LH2.4's interface functions. It was improved in later production -561 ECUs and used in the -951 version which dropped support for the cold start injector.

Ya, I thought I would get lucky by replacing the TIPxxx something-or-other drive transistors, but to no avail. Of course the problem was much deeper than that, and without a schematic I was more concerned about getting my car back on the road than spending a lot more time reverse-engineering the damn thing. Might make a good retirement project down the road...

Retirement project? Take a look at your old one, presuming you've found a replacement ECU to get your car back on the road. Unless you could deal in thousands quantities, the work to duplicate that circuit, of which the fuel pump part is a miniscule portion, has no reward I can imagine. Not when there are megasquirts to play with, for example.

If junkyard replacements really get scarce, substituting a K-jet relay to preserve the safety, if not plug and play, is a viable alternative. ColinUK and Lucid have provided step-by-steps; Chrissij pointed out valid caveats in the way of consequences to subsequent owners, if any of us actually consider selling our bricks once so modified.

TIP transistors? For injector drive, idle motor and on-board +5 regulator, but none of the relay drivers... they're mostly 150mA TO-92 on the earlier ECUs, and, except for the hybrid surprise on that fuel pump relay, in an 18-pin dip array on the LH2.4.

Area of hybrid from where fuel pump relay is driven (pin 3) on the failure-prone hybrids.



Same area on the improved hybrids.

Unfortunately I handed back my old one for the core return. Thanks for the tips (TIPs?!) Art. Are you referring to the DIP18 with the inhouse part number and Bosch logo on it? Have you ever found one with an industry-standard part number on it or is it custom silicon as far as you know?

Good pics too, btw. FINALLY some decent shots on this board that aren't big blobs of blackness that leave an aweful lot to the imagination. Is that you using a laser on the top pic near the rightmost cap? ;)

Guess those pics reveal more than I knew-- can you see my reflection in the gel? Thanks, but the only lasers I have won't trim resistors;-)

To answer your question about the 18-pin dip I had to dig out the notes I made about two years back. That is the Bosch labeled part "30047" at BS-203. But in my notes, I traced the pin 21 ign switch signal supplying a ground to the "main" relay portion of the fuel injection duo, not to the 30047 I concluded was a transistor array, but to a discrete T-305. The effect of the circuitry here is to keep power to the AMM for the burnoff function time after ignition key is shut off.

But the 18-pin array, if that's what it is, drives a bunch of external things like the rpm or load signal, actual AMM burnoff signal, check engine lamp, shift indicator/OD lamp (which still confuses me as the pin is obviously an output even though the OD lamp is sourced at the OD relay) and as an input, looks at the VSS signal provided by the speedo board.

I was tracking the reason for a very hot R315 on a -933 EGR version I found in our non-EGR 89 245. Then I gave some thought to the BS-203 with the Bosch p/n being a private labeled standard (probably just wishful thinking) transistor array, but lost interest when I found the warm resistor had nothing to do with the particular failure in the -933.
--
Art Benstein near Baltimore Crrrrazy Ray's!

Art, thanks for your input. It could be a $2 for a new transistor on LH 2.2 and almost impossible to repair on LH 2.4, I don't think it's a good idea to go with a soldering iron into a ceramic hybrid circuit ;)

BTW, I found a great page with pin tables for almost all Bosch ECUs.
http://www.carsoft.ru/avtorepair/ecm/ecm.html

This page is about LH 2.4.2 for Saab 900, but it's very close to 2.4 for Volvo.
http://www.scotsglen.com/saab/ecu/LH242/LH242_main.htm