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Engine-Codes – Subaru – P1133 Subaru

P1133 Subaru Code - Front Oxygen Sensor Heater Circuit High Input

Quick Answer

The P1133 code for Subaru vehicles indicates a problem with the front oxygen sensor heater circuit, specifically a high input. Common causes include Faulty Front Oxygen Sensor: The front oxygen sensor itself may be faulty and not heating up properly, Damaged Wiring Harness: The wiring harness connecting the front oxygen sensor to the ECM may be damaged or have a poor connection, Blown Fuse: A blown fuse in the oxygen sensor heater circuit can prevent the sensor from heating up. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P1133 Subaru indicates Front Oxygen Sensor Heater Circuit High Input.
Common causes
Common causes include Faulty Front Oxygen Sensor: The front oxygen sensor itself may be faulty and not heating up properly, Damaged Wiring Harness: The wiring harness connecting the front oxygen sensor to the ECM may be damaged or have a poor connection, Blown Fuse: A blown fuse in the oxygen sensor heater circuit can prevent the sensor from heating up.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
What is this?
Table of contents Created and updated by William Orellana on Sep 10, 2024
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Code P1133 Subaru Description

The P1133 code for Subaru vehicles indicates a problem with the front oxygen sensor heater circuit, specifically a high input. The front oxygen sensor, also known as the upstream oxygen sensor, is responsible for measuring the oxygen content in the exhaust gases and providing feedback to the engine control module (ECM) to adjust the air-fuel mixture for optimal combustion. The heater circuit in the oxygen sensor is designed to reach operating temperature quickly to improve accuracy and efficiency.

OBDII Code P1133 Subaru - Front Oxygen Sensor Heater Circuit High Input
P1133 Subaru Code - Front Oxygen Sensor Heater Circuit High Input

Common Causes of P1133 Subaru

  1. Faulty Front Oxygen Sensor: The front oxygen sensor itself may be faulty and not heating up properly.
  2. Damaged Wiring Harness: The wiring harness connecting the front oxygen sensor to the ECM may be damaged or have a poor connection.
  3. Blown Fuse: A blown fuse in the oxygen sensor heater circuit can prevent the sensor from heating up.
  4. ECM Issue: A problem with the engine control module (ECM) could also trigger this code.

Symptoms of P1133 Subaru

  1. Check Engine Light: The most common symptom associated with this code is the illumination of the check engine light on the dashboard.
  2. Reduced Fuel Efficiency: A malfunctioning front oxygen sensor can lead to a rich or lean air-fuel mixture, resulting in decreased fuel efficiency.
  3. Rough Idle: An improperly functioning front oxygen sensor can cause the engine to idle roughly or stall.
  4. Failed Emissions Test: If the front oxygen sensor is not working correctly, the vehicle may fail emissions tests due to increased emissions.

How to Fix P1133 Subaru

  1. Diagnose the Issue: Use an OBD-II scanner to retrieve the fault code and determine if the front oxygen sensor heater circuit is indeed the problem.
  2. Inspect Wiring and Connections: Check the wiring harness and connections for any damage, corrosion, or loose connections. Repair or replace as needed.
  3. Test Oxygen Sensor: Test the front oxygen sensor to see if it is heating up properly. Replace if necessary.
  4. Check Fuses: Inspect the fuses related to the oxygen sensor heater circuit and replace any blown fuses.
  5. Clear Codes: After making the necessary repairs, clear the fault codes with the OBD-II scanner and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P1133 Subaru

The typical repair costs for a P1133 code on a Subaru vehicle can range from $150 to $400, depending on the specific cause of the issue and the cost of parts and labor. This estimate includes the cost of a new front oxygen sensor, wiring repairs, and diagnostic time. It's important to note that labor rates at auto repair shops can vary, with hourly rates typically ranging from $80 to $150. Additional costs may apply if the ECM needs to be replaced or if other underlying issues are discovered during the repair process. It's recommended to obtain a detailed quote from a trusted mechanic or dealership for a more accurate estimate based on your vehicle's make and model.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P1133 Subaru Code

1. What does the OBDII code P1133 mean on a Subaru?

P1133 indicates a "Front Oxygen Sensor Heater Circuit High Input," meaning there is a problem with the heating element of the upstream oxygen sensor.

2. What are the symptoms of a P1133 code on a Subaru?

Common symptoms include a check engine light, poor fuel efficiency, rough idling, reduced engine performance, and difficulty passing emissions tests.

3. What causes the P1133 code on a Subaru?

The most common causes are a faulty oxygen sensor, damaged wiring or connectors in the sensor circuit, or an issue with the engine control module (ECM).

4. Can I drive my Subaru with a P1133 code?

While you can drive with this code, it’s not recommended because it may lead to poor fuel economy and long-term damage to the engine or catalytic converter.

5. How do I diagnose the P1133 code on my Subaru?

Start by inspecting the wiring and connectors for the front oxygen sensor, then test the heater circuit using a multimeter to check for proper resistance.

6. Does a P1133 code mean the oxygen sensor needs to be replaced?

Not always. While a faulty sensor is a common cause, the issue could also be with the wiring, connectors, or ECM. Proper diagnosis is essential.

7. How much does it cost to fix the P1133 code on a Subaru?

Replacing the oxygen sensor typically costs $150–$300, including parts and labor, but prices may vary depending on the model and location.

8. Can a dirty air filter cause the P1133 code?

No, a dirty air filter is not directly related to this code, as it specifically points to the oxygen sensor heater circuit.

9. How do I reset the P1133 code after repairs?

You can reset the code by using an OBDII scanner or by disconnecting the battery for 10–15 minutes, but only after ensuring the issue is fixed.

10. What happens if the P1133 code is ignored?

Ignoring the code can lead to worsened fuel economy, increased emissions, and potential damage to the catalytic converter over time.

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