My wife has a 99 Accord that was declared a gross polluter. She has just over 90K miles and the car runs well, except for an intermittent idle drop. The only codes shown are P1166 and P1167, both of which relate to the heater. I don't know how that affects emissions.

Anyone have any ideas?

 

Those codes refer to the heater circuit of your primary O2 sensor. That controls your air/fuel ratio.

P1166 Heated Oxgen Sensor Sensor1 (Primary HO2S) Heater Circuit Malfunction Comprehensive
(HO2S)
P1167 Air/Fuel Ratio (A/F) Sensor (Sensor 1) Heater System Malfunction A/F sensor heater

Check the fuse that is mentioned in the link below. Check that the connection at the O2 sensor is properly plugged in and the contacts are clean. The sensor is bolted into the exhaust manifold towards the bottom.

Here is a link from someone that had an identical problem to you.

https://www.hondaaccordforum.com/m_9..._1/key_/tm.htm

 

Thanks for the info and fast response.[8D]