ants99

Im currently trying to smog my car, but an engine code keeps appearing and disapering, and the only way to get this code, is by pulling over and checking it once it seems.
I've already changed the spark plugs and coils, Checked all leaking vacuum lines, and replaced the capacitors inside the ECU, I'm not sure what to do other than replacing the o2 sensor,
It's just strange that the engine light goes away and comes back, can anyone explain this?

Arsenii

Hello,

Code 28 means that there is an issue with the Heater in the O2 sensor, which is just a coil that heats the sensor for more efficient operation, and that can eventually snap with all the heat/cool cycles. The crack can be small enough for the heater to regain contact when it is hot or cold, but then break again as material expands, which can explain why the issue is intermittent. What you can do is swap two sensors around to see if the code will switch to the other bank, if so, you will know for a fact that it is the sensor that is out, but I am not sure if it is worth the trouble, considering what a pain those usually are to remove.

Hope this helps and best of luck!

ants99

Thank you sm!!! this clarifies a lot, i was going to replace the MAF lmao, do you think if I replace the O2 sensor it would fix the problem?

Arsenii

Unplug the affected O2 sensor and check resistance between two Black wires, while also wiggling the wiring to make sure you exclude a chance that there is a break in the connection. If there is no resistance, the sensor is a goner and needs to be replaced. If there is resistance, check that you get 12V at corresponding wires when the Ignition is ON, if so, swap the sensors around and see if the code will switch, which will indicate if there is a barely noticeable break in the wiring or corrosion in connection.

Hope this helps and best of luck!