DTC Advanced Diagnostics: P0134 (3.5L Engine)
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 a heater and by maintaining a steady high temperature to accurately calculate the air/fuel ratio. If the heater does not properly heat the element, the rear A/F sensor (bank 1, sensor 1) does not activate, and the exhaust emissions deteriorate. The powertrain control module (PCM) monitors the rear A/F sensor (bank 1, sensor 1) internal resistance.
- When the rear A/F sensor (bank 1, sensor 1) does not activate for a set time after the rear A/F sensor (bank 1, sensor 1) heater is turned on (with high rear A/F sensor (bank 1, sensor 1) internal resistance), a malfunction of the rear A/F sensor (bank 1, sensor 1) heater is detected, and a DTC is stored.
- When the rear A/F sensor (bank 1, sensor 1) heater cycles ON and OFF for a set time, and the resistance remains high when the heater is ON, a malfunction of the rear A/F sensor (bank 1, sensor 1) heater is detected, and a DTC is stored.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Continuous |
| Sequence | None |
| Duration | 40 seconds or more* 1 (90 seconds or more)* 2 |
| DTC Type | Two drive cycles, MIL on |
*1: USA/Canada models
*2: Mexico models
Enable Conditions
| Condition | Minimum | Maximum |
|---|---|---|
| 12 volt battery voltage [Battery] | 10.5 V | - |
| Fuel feedback | Other than during fuel cut-off operation | |
[ ]: HDS Parameter
Malfunction Threshold
- Malfunction determination 1 - From start up
The rear A/F sensor (bank 1, sensor 1) internal resistance value is 200 Ohm or more for at least 40 seconds or more* 1 (90 seconds or more)* 2 right after the engine starts.
- Malfunction determination 2 - Hot
The rear A/F sensor (bank 1, sensor 1) internal resistance value is 270 Ohm or more for at least 1.0 second.
Possible Cause
The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
- Rear A/F sensor (bank 1, sensor 1) heater failure
- Rear A/F sensor (bank 1, sensor 1) element failure
- Rear A/F sensor (bank 1, sensor 1) VSB1 line open
Confirmation Procedure
Operating Condition
Start the engine, and let it idle for at least 1 minute. When engine coolant temperature [ECT Sensor 1] is 5.1 deg.F (-14.9 deg.C) or less, let the engine idle for at least 3 minutes.
Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC, the freeze data, and the on-board snapshot are stored.
Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, the freeze data, and the on-board snapshot can be cleared with the scan tool clear command.