Toyota Error Code P2238 – A/F Sensor Positive Current Control Circuit Low

🔍 What Does Toyota Error Code P2238 Mean?

P2238 – A/F Sensor Positive Current Control Circuit Low indicates that the ECM has detected a low voltage condition in the air-fuel ratio sensor circuit. Specifically, the positive current circuit responsible for controlling the A/F sensor is below the expected threshold. This usually relates to the upstream sensor (Bank 1 Sensor 1), which directly affects how fuel is metered.

📍 Why P2238 Appears

• The air-fuel sensor is not sending enough current due to circuit resistance or a short
• The ECM cannot properly adjust the fuel mixture due to inaccurate readings
• This code often occurs after sensor degradation, wiring issues, or contamination

⚠️ Common Symptoms of P2238

• Check Engine Light (CEL) illuminated
• Rough idle or hesitation under load
• Decreased fuel efficiency
• Smell of unburned fuel in exhaust
• Loss of power in some driving conditions

🔎 Common Causes

• Faulty or degraded A/F sensor (Bank 1 Sensor 1)
• Open or short in A/F sensor positive current control wiring
• Poor electrical ground or corroded connector terminals
• Contaminated sensor due to oil, coolant, or silicone vapor
• Faulty ECM (rare)

🧰 How to Diagnose Toyota Code P2238

1. Connect a diagnostic scanner capable of viewing A/F sensor voltages
2. Confirm freeze frame data and look for additional codes like P2195 or P0130
3. Use a digital multimeter to test voltage between the sensor’s positive control wire and ground (should not be 0V)
4. Inspect the harness from sensor to ECM for chafing or damage
5. Test resistance in the sensor’s heater circuit and current control wires
6. Check for contamination (e.g., oil leaks near exhaust or silicone spray inside air intake)

🔧 How to Fix Toyota Error Code P2238

1. Replace the A/F ratio sensor with a high-quality or OEM-grade sensor
2. Clean connectors and ensure a solid ground and voltage supply
3. Repair or replace any damaged or shorted wiring to the sensor
4. Clear the codes and perform a drive cycle test
5. If issue persists, consider ECM testing or reflashing at a Toyota dealership

💰 Estimated Repair Costs

• A/F Sensor Replacement (Bank 1 Sensor 1): ₱3,500 – ₱6,000
• Wiring Repair or Connector Replacement: ₱1,000 – ₱3,000
• Diagnostics & Labor: ₱1,000 – ₱2,000
• ECM Testing or Reprogramming (if needed): ₱3,000 – ₱5,000

🧠 Expert Tips

• Always replace A/F sensors with Denso, NTK, or original Toyota parts to avoid premature failure
• Avoid using silicone sprays or sealants near the air intake – they damage O2/A/F sensors
• Test and confirm voltages and resistance before replacing the sensor to avoid misdiagnosis
• If multiple codes are present, fix those first – P2238 may be a result of another upstream fault

❓ FAQ – Toyota P2238

Can I drive with code P2238?

Yes, but it’s not recommended for long periods. Fuel mixture may become too lean or rich, affecting drivability and emissions.

Is P2238 the same as an O2 sensor issue?

Not exactly. It relates specifically to the A/F (air-fuel) sensor, which is more advanced and provides a broader, more precise signal than a basic O2 sensor.

Does cleaning the sensor fix this?

No. A/F sensors are sealed components. If it’s faulty or contaminated, replacement is required.

Will this code turn off after replacement?

Yes, if the root cause (sensor or wiring) is fixed. Always clear the code after repairs and test drive the vehicle to confirm.

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