986 Different ABS versions

[Marc_986]

Some update on this topic.

The ABS 5.3 seems to have thin film technology electronics, so modifying this to accept the hall sensors is out of the question. It should be quite possible to mimic the inductive sensor with a small circuit, but I do not want to risk anything here in the brake circuit, it is kind of critical.

So either I should just accept not having ABS (not mandatory by law to have it operational) or I should upgrade to ABS 5.7

Mechanical / Hydraulic it isn't very difficult. I'll need to swap ABS units with hardlines to MC and to the 'adapter' in the wheel well. From there the front lines will plug right in, but I'll need the additional rear brake line for the separate circuits. That might be a good thing actually as the connection to the brakes hoses is seized and I'd like to put new hoses on.

Then on to the electrical side. This is a bit more complicated and I'm not sure whether my wiring diagram is correct (Bently manual doesn't have the ABS 5.7 in, it falsely lists ABS 5.3 to be the only one available). It has a different connector, but 90% of the wires (and colors) are the same. So if length of wire is enough I should be able to crimp new terminals on. All good.

The differences I see so far;
- The brake light switch should run two wires (NC and NO) instead of single wire.
- The e-brake switch is connected on ABS 5.7, but I see no reason to wire it up.
- ABS 5.7 normally sends speed info over CAN to the instrument cluster, but it seems like the pulse output is still present.
- ABS5.7 has an additional fuse on it's power.
- There is no ABS light (instrument cluster) signal present on ABS5.7. Likely this will be send over CAN as well. The PSM5.7 wiring diagram I have does show the signal, just left unconnected.

Does anyone know whether the ABS5.7 actually has this signal (ABS-SILA) implemented? So far this seems to be the main challenge. I guess I could always take it from the CAN bus and convert to single IO to drive the cluster. That would require a small microcontroller.

Also, any ABS 5.7 wiring diagram out there which is known to be accurate?