Found an excellent site that displays wiring diagrams for the following ECUs & Ignition Systems:

CI-fuel injection, B200/230 E
Motronic, B200/230ET
LH-Jetronic 2.2, B230FT
LH-Jetronic 2.4, B230F
LH-Jetronic 2.4, B234F, B204E
Regina, B234F, USA Federal

EZ 116K Ignition system, B230F
EZ 116K Ignition system, B234F, B204E
EZ 117K Ignition system, B230FT
EZ 118K Ignition system, B230K, B200/230E
Rex i Ignition system, B234F USA, Federal
Renix ignition system, B200K

Wiring diagrams for ECUs & Ignition Systems on 740s upto 1989

Noel

Yep...they would be straight out of the Volvo manuals.

Chris

Looks like Euro manuals too, with some US. Couple years ago the same site had internals for a couple Bosch ECUs, Motronics if I recall.

As Noel was recently tracing his constant idle system disable pigtail, I'm sure he will notice the LH2.2 ECU depicted has two pin 12's.
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Art Benstein near Baltimore

Hi Art,

Yes - just like you'd indicated in the IAC thread, Pin 12 on the ECU is also connected to 15 on the ICU. That's the reason for those 2 pin-12s.

I've given up trying to disable the IAC via the grounding of pin 12 - just dont get any rpm change. The engine is idling nicely now at around 750. Idle-Bypass screw is fully closed to compensate for very-slightly open butterfly-valve. Never had the car start and idle as well as it currently does: on cold, it surges to 1200 rpm on start, and slowly (5 secs or so) settles to 750. Certainly worth all that extra effort. Couldn't have done it without you'll - so thanks a lot !

Over the weekend I turned my attention to setting the CO level. I have a spare AMM that had the adjustment-screw plug removed, so I swapped that with my current AMM. Both the AMMs had their pot.resistance set to around 380 ohms (didn't check the voltage as you reccomended since I didn't know what pins to check on the ECU at the time). Before I started adjusting the pot - I checked and found that 15 full 360-degree adjustment turns is all it takes to go the full range of the pot. When I rigged up the test LED-circuit between ECU pins 22 and +12v, I found it was lit up all the time. After adjusting the pot almost all the way to one end, it started blinking nice and steady. I then rigged up the LED so I could drive and watch how the rich/lean settings changed while driving. Experiment was so interesting I plan on rigging the LED up permanently using a spare dash bulb-socket.

After I finished my adjustment, I checked the resistance & voltage. Resistance between AMM Pin 6 and ground (or Pins 1,3 or 4) is around 100 ohms. Voltage between Pin 6 and ground is a mere 0.55 volts. Is this resistance/voltage setting way off ? As I said - test LED blinks nice and steady (about 50% duty-cycle as best I can tell). To make sure there was no wire-resistance coming into play, I verified these values at the ECU pin 14 as well. I suspected my Bosch O2 sensor might be off (it's 8 years old now) - but I tested it and it generates a healthy 0.2 -> 0.9 v - so no reason to change it.

So I guess my tune-up is done (though I still need to replace my 8-year fuel-filter & original filter-sock). Am curious to see what my next CA emission test report is: I keep all back reports for comparison, but this will be the first one on a dyno. They've never raced the engine on park in previous tests because the ZF22 warning immediately pops-up on all their test-rigs.

I've made so many tuning-changes now I'm curious to see how much (if any) it affects mileage.

Thanks for all your help !

Noel

leave it to the Russians.....
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1991 740 B230F 135K miles

Great find, hopefully Steve Ringlee will see this and add it to the FAQ. If not, one of us can email him.

Thanks,
Bean
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'80 242GT 93k, '94 945T 139k, '89 765T 68k (new '94 B230FT)

This is very, very cool. As an owner of an 89 740, this should prove to be very helpful.

Thanks