P0038 – HO2S Heater Circuit High (Bank 1 Sensor 2)

Quick answer

• What it means: The P0038 code indicates that the oxygen sensor heater circuit for Bank 1 Sensor 2 has a voltage reading that is higher than expected.
• Severity: This is a moderately severe code. While your car may still be drivable, prolonged driving can lead to increased emissions and potentially damage the catalytic converter.
• Most common cause: A short to power in the heater circuit wiring or a faulty oxygen sensor heater element.

What the P0038 code means

The official OBD-II definition for P0038 is "HO2S Heater Circuit High (Bank 1 Sensor 2)". In simpler terms, this means that the powertrain control module (PCM) has detected an abnormally high voltage within the heater circuit of the downstream oxygen sensor on Bank 1. Bank 1 refers to the side of the engine that contains cylinder #1. Sensor 2 indicates that it is the oxygen sensor located after the catalytic converter.

Oxygen sensors require heat to operate efficiently. This is especially true during cold starts when the exhaust gases aren't hot enough to bring the sensor up to its operating temperature quickly. A small heating element inside the oxygen sensor rapidly warms it up. When the PCM detects a voltage in this heater circuit that is outside of the specified range (too high in this case), it sets the P0038 code.

Common symptoms

• Check Engine Light illuminated
• Reduced fuel economy
• Increased emissions (may not be noticeable to the driver)
• Engine running rough or hesitating (less common, usually indicates a more severe underlying issue)

Common causes

1. Short to power in the HO2S heater circuit wiring: This is often the most common cause. A damaged wire shorting to a constant power source can send an elevated voltage to the sensor heater circuit.
2. Faulty oxygen sensor (Bank 1 Sensor 2): The heating element within the oxygen sensor itself can fail, leading to an abnormally high resistance or an internal short, causing the PCM to detect high voltage.
3. Corroded or damaged electrical connectors: Water intrusion, corrosion, or physical damage to the connector leading to the oxygen sensor can disrupt the circuit and cause voltage discrepancies.
4. Faulty PCM: While rare, a defective PCM could incorrectly interpret voltage readings or fail to properly regulate the heater circuit. This is typically diagnosed after all other possibilities have been ruled out.

How a technician diagnoses it

1. Verify the code and check for other DTCs: The technician will connect an OBD-II scan tool to confirm the P0038 code and check for any other related or accompanying diagnostic trouble codes. They will also look at freeze-frame data to understand engine conditions when the code was set.
2. Visual inspection: A thorough visual inspection of the Bank 1 Sensor 2 oxygen sensor and its wiring harness will be performed. The technician will look for signs of damage, fraying, corrosion, or burnt wires.
3. Inspect electrical connectors: The electrical connector for the oxygen sensor will be disconnected and inspected for bent pins, corrosion, or loose connections.
4. Test heater circuit power and ground: Using a multimeter, the technician will check for proper voltage supply and ground at the oxygen sensor connector. They will look for approximately 12 volts to the heater circuit and a good ground connection. A high voltage reading here could indicate a short to power.
5. Test oxygen sensor heater element resistance: The technician will measure the resistance of the oxygen sensor's heater element using a multimeter. Compare this reading to the manufacturer's specifications. An open circuit (infinite resistance) or a short circuit (very low resistance) within the heater element would indicate a faulty sensor.
6. Scan tool data review: Live data from the scan tool will be monitored to observe the oxygen sensor heater circuit voltage and current. A constant high voltage reading without proper regulation would point towards a circuit issue or sensor failure.
7. Wiggle test: With the engine running and the scan tool monitoring live data, the technician may gently wiggle the wiring harness of the oxygen sensor to see if it causes any fluctuations in the readings, indicating an intermittent connection or short.

Typical repair cost

The cost to repair a P0038 code can vary depending on the diagnostic time and the specific component that needs replacement.

• Oxygen sensor replacement: $200 - $450 (parts: $80 - $200, labor: $120 - $250)
• Wiring repair: $50 - $200 (labor: $50 - $150, small parts may be negligible)
• Connector replacement: $75 - $250 (parts: $15 - $50, labor: $60 - $200)

These estimates do not include potential diagnostic fees, which typically range from $80 to $150.

Can I keep driving with this code?

While you can typically drive with a P0038 code without immediate catastrophic failure, it is not recommended to do so for an extended period. The primary reason is that the faulty oxygen sensor will not be providing accurate data to the PCM, leading to incorrect fuel mixture adjustments. This can result in:

• Reduced fuel efficiency
• Increased harmful emissions
• Potential long-term damage to the catalytic converter due to rich or lean running conditions.

It's best to address this issue as soon as possible to prevent more costly repairs down the line.

Related codes

• P0036: HO2S Heater Control Circuit (Bank 1 Sensor 2)
• P0037: HO2S Heater Circuit Low (Bank 1 Sensor 2)
• P0056: HO2S Heater Circuit (Bank 2 Sensor 2)
• P0057: HO2S Heater Circuit Low (Bank 2 Sensor 2)
• P0141: O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

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