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Julian,
I prefer the 'measure thrice, cut once' method of troubleshooting. Some - and there're lots of them and I don't like them - prefer carelessly and thoughtlessly swapping parts here and there until the issue is resolved (as they think, but often it's not the case though it may look this way) or they're out of money or out of parts.
I'd try to keep it in a simple English so instead of shunt resistance voltage drop and other moonspeak I'll say that the ECU needs to know whether it can safely operate the load or the load is faulty and short-circuit and it's better to leave it alone and go into safe-mode. It spells 'abra-kadabra' and then checks what it comes up with. So when the ECU is telling you that other thing is faulty it means that either that thing is faulty or the ECU lost its magic and no longer correctly spells that spell. Or the wiring between them is corrupt.
So let's check your ABS valve-block. Since the ECU built-in diagnostics procedures don't tell us whether it is in-let or out-let Front-Right valve (yep, there two valve per a front wheel in ATE ABS MkII system), we need to check both of them.
Pickup your ol'good trusty ohm-meter (or a multimeter set to work in the ohm-meter mode) and hook up to the valve-block connector having the wiring connector un-plugged from that boy. Check the resistance across pins 1 and 7. Saab doesn't specify the in-spec resistance for this device so you've got to remember this value and compare it to one from another one: so having one probe still connected to the pin 1 hook the other one up with pin 2 (this is a pin for the Front Left Inlet valve winding; we've got to compare apples to apples and I suspect that inlet and outlet valves may have different winding resistances, let alone the rear-axle channel with its valves). If the measured values differ more than 50%, then I'd suspect the IFR valve winding to be faulty.
But you've got to complete the checking procedure and thus you still have to compare the resistances across pins 1-6 and 1-3.
If the 1st step doesn't bring you a definite result, then check the wiring and plug the valve-block connector back to the valve-block and go under the rear seat and disconnect the wiring connector from the ABS ECU and repeat the test procedure across the pins OF THE WIRING CONNECTOR, NOT ON THE ABS ECU CONNECTOR PINS. The pins (or better say, the resistances measured across the pins) to be tested are 11-15 vs 11-35 and 11-34 vs 11-16. If the resistance between pins 11-15 is about the same as the resistance across pins 11-35 and the resistance across pins 11-34 looks similar to one between pins 11-16 of the wiring loom connector, then the ABS ECU is faulty and no longer correctly spells that very 'abra-kadabra' and should be replaced. If the IRF/ILF and ORF/OLF resistances are the same at the valve-block but differ when measured along the wiring then the wiring is defective and should be repaired. If the resistances are different when measured at the valve-block, then the valve-block is faulty and should be replaced.
I hope that I've made this clear and that it helps.
Zig
P.S.
The ABS electric wiring diagram in both Bentley Talmud and Saab Service Manual aren't very clear about the pin numbers on the valve-block side. So I think even if you troubleshoot the valve-block to be faulty it's still worth to confirm the results completing the checks across the wiring from the ABS ECU side.
posted by 5.18.17...
, Wed, 20 May 2015 12:39:37
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