Advanced Diagnostics

DTC P0134: Rear Air/Fuel Ratio (A/F) Sensor (Bank 1, Sensor 1) Heater System Malfunction




General Description
The rear air/fuel ratio (A/F) sensor (bank 1, sensor 1) is activated by warming the element with the heater any by maintaining it at a steady high temperature to accurately calculate the air/fuel (A/F) ratio. The rear 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 powertrain control module (PCM) monitors the rear A/F sensor internal resistance.

1. When the rear A/F sensor does not activate within a set time after the rear A/F sensor heater starts to warm up (with high rear A/F sensor internal resistance), a malfunction of the rear A/F sensor heater is detected, and a DTC is stored.
2. When the rear A/F sensor heater cycles ON and OFF within a set time, and the resistance remains high when the heater is ON, a malfunction in the rear A/F sensor heater is detected, and a DTC is stored.

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




Monitor Execution, Sequence, Duration, DTC Type, OBD Status




Enable Conditions

Malfunction Threshold

Malfunction determination 1
The rear A/F sensor (bank 1, sensor 1) internal resistance value is 110 ohms or more for at least 40 seconds right after the engine starts.

Malfunction determination 2
- The rear A/F sensor (bank 1, sensor 1) internal resistance value is 110 ohms or more for at least 15 seconds.
- The rear A/F sensor (bank 1, sensor 1) internal resistance value is 200 ohms or more for at least 1 second.

Driving Pattern
Start the engine, then let it idle for at least 2 minutes.

Diagnosis Details

Conditions for illuminating the MIL
When a malfunction is detected during the first drive cycle, a Temporary DTC is stored in the PCM memory. If the malfunction recurs during the next (second) drive cycle, the MIL comes on and the DTC and the freeze frame data are stored.

Conditions for clearing the MIL
The MIL will be cleared if the malfunction does not recur during three consecutive trips in which the diagnostic runs.

The MIL, the DTC, the Temporary DTC, and the freeze frame data can be cleared by using the scan tool Clear command or by disconnecting the battery.