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Generic. Do 4 wire post cat O2 sensors use the heater constantly or does it switch on / off?
Specific. Car in question is a 2003 Vauxhall Corsa 1.0L. MIL light on and scanner showing DTC for bank 1 sensor 2 heater inactive. Live data showed OS2 heater as constantly inactive, constant 450mV output. Sensor replaced and DTC cleared. With new sensor in place and scan tool reconnected initially the DTC returned, live data shows the constant 450mV output still and the heater shows mostly inactive and briefly switches to active every few minutes. I've cleared the DTC again and got the battery disconnected to reset ECU so hoping when reconnected all will be well but not sure if the heater circuit should be switching as it is.
Griggs wrote: Do 4 wire post cat O2 sensors use the heater constantly or does it switch on / off?
It depends. :silly: Different makes will have different strategies for their downstream heaters. Nissan, for example, usually won't run their downstream heaters at all at idle. GM will run their heaters at idle, but at a varying pulse width.
Specific. Car in question is a 2003 Vauxhall Corsa 1.0L. MIL light on and scanner showing DTC for bank 1 sensor 2 heater inactive. Live data showed OS2 heater as constantly inactive, constant 450mV output.
What's the code, specifically? We want to know if the code it setting because the ECM detects a heater circuit problem, or it's watching the O2 signal and inferring heater performance.
Tyler wrote:
What's the code, specifically? We want to know if the code it setting because the ECM detects a heater circuit problem, or it's watching the O2 signal and inferring heater performance.
Thanks Tyler. Afraid I have to hang my head in shame and admit schoolboy error that in my haste I didn't write down the code :blush: :blush:
Battery reconnected now and code not returned. Watching live data it appears that the heater is switched as described above at idle, as RPM and mV output raised then the heater spends more time in active mode.
