DTC Advanced Diagnostics: P0155 (3.5L Engine)
DTC P0155: Front Air/Fuel Ratio (A/F) Sensor (Bank 2, Sensor 1) Heater Circuit Malfunction
General Description
A heater for the sensor element is embedded in the front air/fuel ratio (A/F) sensor (bank 2, sensor 1), and it is controlled by the powertrain control module (PCM). It is activated and heats the sensor to stabilize and speed up the detection of oxygen content when the exhaust gas temperature is cold. The PCM monitors the front A/F sensor (bank 2, sensor 1) heater output (return check). If the return signals do not meet the command value (for heater activation) for a set time, the PCM detects a malfunction and stores a DTC.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Continuous |
| Sequence | None |
| Duration | 5 seconds or more |
| DTC Type | Two drive cycles, MIL on |
Enable Conditions
| Condition | Minimum | Maximum |
|---|---|---|
| 12 volt battery voltage [Battery] | 9.0 V | - |
| State of the engine | Running | |
| Other | During front A/F sensor (bank 2, sensor 1) heater operation | |
[ ]: HDS Parameter
Malfunction Threshold
One of these conditions is met for at least 5 seconds.
- No return signal "HIGH" is detected when the PCM output duty is less than 5 %.
- Return signal does not change when the PCM output duty is 5 %* or more.
*: PCM output duty is limited to 95 % when it exceeds 95 %.
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.
- Front A/F sensor (bank 2, sensor 1) failure
- Front A/F sensor (bank 2, sensor 1) AFTHB2 line open
- Front A/F sensor (bank 2, sensor 1) AFTHB2 line short to ground
- Front A/F sensor (bank 2, sensor 1) heater power supply line open
Confirmation Procedure
Operating Condition
Start the engine. Hold the engine speed [Engine Speed] at 3, 000 RPM without load (in P or N) until the radiator fan comes on.
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.