Hi,
I'm hoping someone out there can save me some time and tell me where the LH F.I. diag. connector under the hood gets it's power. The one on my car is not working (no flashing LED) and I went throught the procedure in the Bentley manual to check for 12 volts at the black and red wire: no power. It then just says to check the wiring diagrams to find the open circuit. I can't find this connector on the diagram, never mind the feed for the 12 volts. Does anyone know the source of power for this connector? All the basics look good: fuses, connections, etc. I even took a shot and swapped the main F.I. relay: no change.
Thanks!

Check fuse #6. The Bentley (Volvo)diagram shows it as main power source for both the FI and Ignition CUs, which feed diag ports 2 and 6.
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

Thank you Bruce. I'll re-check that fuse and the connections to it. I noted the Bentley manual advised removing the connector from the diag. unit and checking for 12V at the black/red wire for LH 2.4 or the blue wire for LH 3.1.
I'll make sure I'm checking the correct wire....pretty sure about it as there are only 4 wires at that connector. I thought that would make it real easy to locate it on the diagram. HAH! Guess my eyes ain't as good as they used to be!

It may not be a fuse #6 problem, since looking at the '89 diagram on 390-46, K-L 4&5 (much clearer), I see the red/black is coming from Ignition Sw #15 to pin 4 on the Diagnostic unit (item 131).

But I really don't know how it works, except that the two ECUs feed into pins 2 and 6—and fuse #6 is common to both.
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

This one sure had me going, as I'm certain I remember a corroded crimp on that obd power lead as someone's problem. Wasn't mine I guess, as my photo recalls fixing the test lead after too much use.

However, looking in Bentley and what green manuals I had showed detail for 90-93 in every case with a blue wire feeding power to the OBD. Our 89 has the red/black. The OBD harness is part of the LH harness, so I'd guess the tie point is where ignition is sent to both ICU and ECU under the glove box area.

Odd, it seems, all the schematics show blue instead of red/black with the distinction between LH2.4 and LH3.1 only cited by the Bentley, where it says check the red/black (LH2.4) or blue (LH3.1) for battery with ignition on.

Couldn't find where I saved your Bentley errata list (!) to see if you already had the funny one in the ignition section p.280-3 Figure 5.

You have got the ignition on? Sorry if you know that - my manual doesn't make that clear, so I wasted ages trying to find why mine didn't work.

A thank-you to Art and Cliff...

After re-checking all the connections and wires that I could get to, I tried swapping out the diagnostic connector. This fixed the problem. I'm guessing either the push-button switch or the LED is bad as the connections looked good. I also removed and replaced the connector several times in case it might be a corrosion build-up issue.

I wish I could get ahold of a set of the Mitchell wiring diagrams for this car. I have one sheet of theirs which covers the rear tailgate section, power mirrors, etc., and it's excellent. Much more readable than the ones in the Bentley manual. I checked their web site and almost had heart failure when I saw their prices.