How about the coolant temp sensor ? This one sends signals to both the ICU and ECU and an intermittent disconnection of this sensor would put the car in a limp mode and restart would remove it from that mode until it happens again. So check its wiring to both the ECU and the ICU, make sure there are no loose connections or cuts in the harness. If that is fine, I would replace that sensor if it has not been replaced recently. Intermittent CPS operation is also a good possibility, but I would assume that the car would most likely stall without the CPS signal. Also hoping that there are no vaccum leaks, i.e. unmetered air entering the intake, that could cause the oxygen signal to reach limits and I am not sure what the ECU would do if it always gets a constant signal. But this you can test and see if indeed the oxygen signal is turning into a DC signal.

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Saumil S. Patel