Replaced O2 with Wideband Sensor: A/F Circuit Issue?

[scribb]

I've installed a Link Storm ECU in piggyback position on a 2005 4Runner. I replaced the upstream 02 sensors with Wideband Lambda sensors, which are running on the CAN circuit, so the original upstream 02 connectors are consequently unplugged. Now I'm getting a parasitic draw that drains the battery overnight. I pulled all the fuses until I isolated the problem to the A/F Heater circuit.

When I first connect the battery, there's no draw. It's only after I start the motor and then stop it, then something on the circuit is remaining open. I can hear a slight buzz, which stops when I pull the A/F Heater fuse. If I put the fuse back in, the problem doesn't recur until the motor is started again.

From what I gather, there are preheaters on the O2 sensor to bring them up to temp in order to operate correctly. If the O2 sensors are deleted, do I need to put a resistor on the circuit or something to prevent the stock ECM from trying to heat the sensors? Or is it likely there's something else going on?

Thanks.

 

[ivan129]

A simple bandaid might be to install a relay that only switches power to the O2 heaters when the engine is running. Engine off, no juice for the O2 heaters, no more problem.

 

[scribb]

Since I don't need the heaters anymore (02 sensors replaced), would a resistor on each sensor circuit eliminate the problem?

 

[ivan129]

Since I don't need the heaters anymore (02 sensors replaced), would a resistor on each sensor circuit eliminate the problem?

Give it a try. Measure the impedance of the heater circuit, calculate the power rating and select a resistor to do the job.

 

[scribb]

One question: I want to rule out any kind of short in the circuit before adding anything. Is this a known issue when replacing 02 sensors? Or should I normally be able to unplug the o2 sensors and not have a significant power draw from trying to heat the old sensors? Thanks!