DTC P0134: Air/Fuel Ratio (A/F) Sensor (Sensor 1) Heater System Malfunction: General Description

The air/fuel ratio (A/F) sensor is activated by warming the element with a heater to maintain it at a steady high temperature for accurate air/fuel (A/F) ratio calculation. The A/F sensor does not become active when the element is not properly heated due to a heater malfunction, and the exhaust emissions deteriorate. The engine control module (ECM) monitors the A/F sensor condition by monitoring the A/F sensor internal resistance.

1. When the A/F sensor does not activate in a set time after the A/F sensor heater is turned on (with high A/F sensor internal resistance), a malfunction of the A/F sensor heater is detected, and a DTC is stored.
2. The A/F sensor heater cycles ON and OFF within a set time. The heater's state is detected by monitoring the internal resistance of the A/F sensor. If the resistance remains high when the heater is ON, a malfunction in the A/F sensor heater is detected, and a DTC is stored.

   Because the degree of effect on engine control differs according to the A/F sensor internal resistance, there are two malfunction detection threshold levels. When either one is reached, a malfunction is detected.