The powertrain control module monitors the heater control circuit for the upstream oxygen sensor on Bank 1 and has detected lower than expected voltage in the positive current control line. This typically indicates a short to ground in the heater circuit, either within the sensor itself or in the wiring harness. The heater is required to bring the sensor to operating temperature quickly for accurate air-fuel ratio readings.
The heating element inside the sensor has developed an internal short to ground or its case, causing excessive current draw that pulls the control circuit voltage low.
The positive heater control wire is chafed, melted, or damaged, creating an unintended path to ground between the sensor and the control module.
Moisture, salt, or corrosion in the sensor's electrical connector creates a conductive path that shorts the heater circuit to ground or alters circuit resistance.
While less common for a 'low' voltage code, an open heater element can occasionally trigger this fault depending on specific ECM detection strategy and circuit design.
The control module's internal transistor responsible for heater current control has failed; this is statistically uncommon and should only be considered after verifying sensor and wiring integrity.
Short-term driving is generally safe, but the engine may run less efficiently and produce higher emissions until the exhaust gas alone heats the sensor to operating temperature.
No. This code refers specifically to the electrical heater circuit of the upstream oxygen sensor, not the catalytic converter's efficiency or storage capacity.
Although the ECM controls the heater circuit, actual failure of its internal driver transistor is rare; the fault is almost always the sensor heater element or the wiring between the sensor and ECM.
It is the oxygen or air-fuel ratio sensor located on the engine bank containing cylinder 1, positioned before (upstream of) the catalytic converter.