AutoCodeFix
🔍
Accident Estimate
EmissionsMinor✅ DIY Friendly

P0138

O2 Sensor Circuit High Voltage Bank 1 Sensor 2

Downstream O2 sensor on Bank 1 reading consistently high voltage.

SeverityMinor
CategoryEmissions
Est. Repair Cost$100–$350
Code TypePowertrain
DIY RepairYes

⚡ Common Causes

  • ›Failed downstream O2 sensor
  • ›Rich exhaust passing through cat
  • ›Fuel-contaminated catalyst
  • ›Faulty sensor

⚠️ Symptoms

  • ›Check engine light
  • ›Failed emissions
  • ›No significant driveability issue

✅ How to Fix — Step by Step

  • Step 1:Replace downstream O2 sensor
  • Step 2:Check for rich condition upstream
  • Step 3:Test catalytic converter
  • Step 4:Inspect fuel injectors for leaks

🔧 Diagnostic Tools Required

Using the correct diagnostic tools helps identify the root cause of P0138 before replacing parts unnecessarily. Always confirm the fault using live data and manufacturer-recommended diagnostic procedures.

💡 Pro Tip: High downstream O2 voltage with no upstream issue often means sensor failure.

Repair Cost Estimate

Full Repair Estimate
$100–$350
DIY Possible?
YES
Severity
Minor

Frequently Asked Questions

What does OBD2 code P0138 mean?+
P0138 stands for O2 Sensor Circuit High Voltage Bank 1 Sensor 2. Downstream O2 sensor on Bank 1 reading consistently high voltage.
What causes code P0138?+
Failed downstream O2 sensor; Rich exhaust passing through cat; Fuel-contaminated catalyst; Faulty sensor
How do I fix code P0138?+
Replace downstream O2 sensor; Check for rich condition upstream; Test catalytic converter; Inspect fuel injectors for leaks
How much does it cost to fix P0138?+
Estimated repair cost for P0138 is $100–$350.
Is P0138 DIY-friendly?+
Yes — P0138 is generally DIY-friendly with basic tools.

AI Diagnosis

🤖 AI-powered diagnosis for P0138 is coming soon.

Related Codes

P0135O2 Sensor Heater Circuit Malfunction Bank 1 Sensor 1
MinorDIY
P0136O2 Sensor Circuit Malfunction Bank 1 Sensor 2
MinorDIY
P0130O2 Sensor Circuit Malfunction Bank 1 Sensor 1
ModerateDIY
P0131O2 Sensor Circuit Low Voltage Bank 1 Sensor 1
ModerateDIY
P0133O2 Sensor Circuit Slow Response Bank 1 Sensor 1
ModerateDIY
P0442Evaporative Emission Control System Small Leak Detected
MinorDIY