DTC Advanced Diagnostics: P2237 (3.0L Engine)
DTC P2237: Rear Air/Fuel Ratio (A/F) Sensor (Bank 1, Sensor 1) Circuit Open
General Description
The rear air/fuel ratio (A/F) sensor (bank 1, sensor 1) is installed in the exhaust manifold and detects oxygen content in the exhaust gas. The rear A/F sensor (bank 1, sensor 1) transmits a signal to the powertrain control module (PCM), and the PCM controls fuel injection duration by comparing the target air/fuel ratio with the rear A/F sensor (bank 1, sensor 1) signal. The rear A/F sensor (bank 1, sensor 1) is composed of detection element, reference oxygen chamber, diffusion chamber, and heater, etc., and enables feedback control of all ranges. If the rear A/F sensor (bank 1, sensor 1) signal AFCB1 or AFVB1 is open circuit, no current will flow to the sensor. Therefore, the element impedance will not decrease even if the element is active. If the element impedance is a set value for a specified duration, the PCM detects a malfunction and stores a DTC.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Continuous |
| Sequence | None |
| Duration | 6 seconds or more |
| DTC Type | Two drive cycles, MIL on |
Enable Conditions
| Condition | Minimum | Maximum |
|---|---|---|
| 12 volt battery voltage [Battery] | 10.0 V | - |
| Rear A/F sensor (bank 1, sensor 1) heater output duty* | 20 % | - |
| State of the engine | Running | |
*: Continues at least 12 seconds[ ]: HDS Parameter
Malfunction Threshold
The calculated element impedance is more than 1, 000 Ohm for at least 6 seconds.
Possible Cause
- Rear A/F sensor (bank 1, sensor 1) AFCB1 line open
- Rear A/F sensor (bank 1, sensor 1) AFVB1 line open
- PCM internal circuit failure
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, then let it idle for 2 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.