This is the code I have:

P0135 Oxygen sensor heater circuit malfunction (pre-converter sensor, left bank) (drivers side)

I have checked out others' experience on the board but still had a question or two. I am aware that I should check for 12V on the black wire in the O2 sensor harness, but here is the issue.

Owing to an over-aggressive use of the head porting grinder, I had a coolant leak into cylinder 7 which was pouring a fair bit of coolant out the exhaust. Could this have caused my o2 sensor heater circuit problem? Will cleaning the sensor likely help? I know that cleaning a really old sensor often doesn't bring it back but since this one only has about 40K miles on it I thought I might be able to save it.

Thanks for the input.

 

Saving it by cleaning would be iffy, IMHO.

 

like rob said cleaning these parts are very hard because of how they read and work!

 

Swap the pre-cat sensors side to side. If the problem follows the sensor to the other side (P0155) its the heater element in the sensor. If the problem stays on Bank 1, its a problem with the wiring or the power source.

The heater element is a simple resistance cricuit. It isn't affected by the gunk on the sensing element, so its hard to see how cleaning the sensor would help, unless the sensor is so badly caked up that its insulating the element from the heat of the exhaust gasses. The PCM diagnostic is checking how long it takes the sensor to reach a particular activity level, which it can't reach until it reaches a high temperature.

It is possible that stuff leaking on the sensor has leaked inside, damaging the internals, including the heater circuit.