However, last night it was showing 150 bar without my foot anywhere near the pedal! And today, when I was getting relatively normal results of 0-40 bar, occasionally it jumped 80 bar! I'm beginning to get to the point of giving up, but thought I'd give you guys one last try. Anyone got any ideas?
Did you hear the ABS pump running, causing the system to be pressurized? This is normal, if the ABS ECU detects some inconsistency, and launches a self-diagnosing routine.
In any case, I recommend that you:
1) install a copy of FiatECUScan on your laptop, plug in your ELM 327 lead, and connect to the ABS ECU.
2) check and note any residual fault codes (with their descriptions) that was left in the ABS ECU memory, then clear them.
3) click on the "Actuator" tab, and run all actuator tests one by one, testing the functionality of the pump, as well as the solenoid valves that pressurizes the various hydraulic lines. Note any behaviour that is inconsistent with the norm, and take it from there. If a new error is generated in the process, you will be able to pinpoint the problem.
The Bosch ABS unit is a solid piece of hardware, that should outlast the rest of the car, if not overly abused. The only included fragile components are some transistors (used for switching the pump and solenoid valves) that easily fails as a result of static electricity and power spikes. These are cheap and fairly easy to replace, whereas replacing the whole ABS unit will be expensive and difficult, including bleeding the hydraulic system, and possibly some reprogramming to pair the new ABS ECU to the body ECU.
You should also do a forum search on ABS related problems, and see if the suggested solutions are applicable for your specific problem, for example: