Code P0135 and the Cooling fans runs all the time

Learn how to fix code P0135 and the cooling fans from run all the time

If you own a Ford Escort or Mercury tracer and encounter a situation where you have a code P0135 and the cooling fans run all the time, you may have a shorted oxygen sensor. The official definition of a P0135 is Oxygen Sensor Heater Circuit Malfunction (Bank 1 Sensor 1). That’s the sensor before the catalytic converter.

Oxygen sensors have a heating element to speed up their ability to sense oxygen in the exhaust stream. However, if that heater shorts out, it draws more current, which can melt the electrical connector, causing another short that powers the cooling fans nonstop. Find the white electrical connector located near the PCM and check for indications of overheated plastic. If the connector is distorted in any way, repair the damage with a new pigtail connector (from Ford) and replace the shorted oxygen sensor, and the problem should disappear.

© 2012 Rick Muscoplat