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I have a 95 M3 3.0L obd1. Getting a lazy O2 signal even after replacement. About .3 hz signal.
I have tested the entire circuit and the relay for the O2 heater circuit is not receiving a ground from the Dme. I’ve tested under different conditions multiple times and the heater relay is never grounded. What are the conditions in which the relay should be turned on? I’m leaning towards a bad Dme.
There is only a single pre cat o2 since this car is obd1.
I replaced the o2 with a Bosch oem unit originally because the waveform was really slow. Almost 4 seconds for 1 complete cycle around .28 hz. Both the old and new o2 are behaving the same. O2 takes a long time to warm up and start working.
Is the heater only supposed to initially heat the o2 or will it help maintain temp and give me a better waveform?
I’ve smoke tested the exhaust and found no leaks. Back pressure was around 0 and barely moved even at 2500 rpm.
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