Faulty air/fuel ratio sensor (bank 1 sensor 2) due to contamination or aging; Exhaust leak before or near the sensor allowing outside air to skew the reading; Wiring damage or corrosion in the sensor circuit, including the connector or harness; Aging or degraded catalytic converter affecting the sensor's response; Engine misfire or vacuum leak causing abnormal exhaust oxygen content; ECM software issue or internal fault in the sensor signal processing circuit

DTC codes / Toyota codes / P1153

P1153 · ToyotaAir/Fuel Sensor Circuit Response Bank 1 Sensor 2

Q: What does code P1153 mean?

Air/Fuel Sensor Circuit Response Bank 1 Sensor 2. P1153 on Toyota vehicles indicates that the engine control module has detected an abnormal response from the air/fuel ratio sensor located after the catalytic converter on bank 1, meaning the sensor's voltage signal is not switching or responding as expected during closed-loop fuel control. The ECM monitors the sensor's output over time and sets this code when the signal remains too flat, too slow, or outside the predicted range for the current operating conditions.

P1153 on Toyota vehicles indicates that the engine control module has detected an abnormal response from the air/fuel ratio sensor located after the catalytic converter on bank 1, meaning the sensor's voltage signal is not switching or responding as expected during closed-loop fuel control. The ECM monitors the sensor's output over time and sets this code when the signal remains too flat, too slow, or outside the predicted range for the current operating conditions.

SystemPowertrain

Code typeToyota specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
A slight decrease in fuel economy as the ECM may default to a richer fuel mixture
Occasional rough idle or hesitation during acceleration if the sensor signal is erratic
Failed emissions inspection due to increased tailpipe emissions
In rare cases, a sulfur or rotten egg smell from the exhaust if the mixture becomes excessively rich

Common causes, most likely first

Faulty air/fuel ratio sensor (bank 1 sensor 2) due to contamination or aging
Exhaust leak before or near the sensor allowing outside air to skew the reading
Wiring damage or corrosion in the sensor circuit, including the connector or harness
Aging or degraded catalytic converter affecting the sensor's response
Engine misfire or vacuum leak causing abnormal exhaust oxygen content
ECM software issue or internal fault in the sensor signal processing circuit

How to diagnose and fix it

Perform a visual inspection of the sensor, its wiring, and connector for damage or corrosion
Check for exhaust leaks upstream of the sensor using a smoke test or by listening for ticking sounds
Use an OBD-II scan tool to view live data for the bank 1 sensor 2 air/fuel ratio sensor and compare to specifications
Test the sensor's heater circuit resistance and verify power and ground at the connector
Inspect the catalytic converter for efficiency using temperature readings or a backpressure test
Replace the air/fuel ratio sensor if diagnostics confirm it is not responding correctly
Clear the code and perform a drive cycle to verify the repair and ensure the code does not return

Don't overlook exhaust leaks and wiring

A small exhaust leak before the sensor can cause a lean reading that mimics a failed sensor, so always smoke-test the exhaust before replacing parts.
The bank 1 sensor 2 air/fuel ratio sensor is often misdiagnosed as a catalytic converter issue, but the sensor itself is frequently the culprit on higher-mileage Toyotas.
Corroded pins in the sensor connector are a common hidden cause, especially in regions with road salt, and can be fixed without replacing the sensor.
This code can be set by a lazy sensor that still produces a plausible signal, so live data graphing is more reliable than a simple resistance check.
After replacing the sensor, the ECM may need a relearn procedure or several drive cycles before the monitor runs and clears the code.

Can I keep driving with P1153?

You can generally continue driving with this code, but avoid prolonged idling or heavy acceleration until it is repaired, as the engine may run richer and reduce fuel economy. Have the vehicle diagnosed soon to prevent potential catalytic converter damage from an overly rich mixture.

Tools that help

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Guidance is general and written for Toyota vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.