p0131
Moderate
Volkswagen · SUVs
O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)
Quick Answer
Error code P0131 on your Volkswagen SUVs means: O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1). This is usually fixable — see the step-by-step guide below.
Affected Models
Likely Causes
  1. Faulty upstream oxygen sensor (Bank 1 Sensor 1)
  2. Exhaust leak before the O2 sensor allowing ambient air to reach the sensor
  3. Damaged O2 sensor wiring, connector, or heater circuit
  4. Persistent lean condition causing sensor to read low voltage
How to Fix It
1
Monitor the upstream O2 sensor voltage with a scan tool at idle and under load; it should oscillate between 0.1V and 0.9V
2
Inspect the O2 sensor connector and wiring for damage, corrosion, or melted insulation
3
Check for exhaust leaks at the exhaust manifold, downpipe, and sensor bung that could introduce false air
4
Test the O2 sensor heater circuit by measuring resistance across the heater element pins
5
Replace the upstream O2 sensor if it is sluggish, stuck low, or has a failed heater circuit
Pro Tip
This fix requires some technical knowledge. If you're unsure about any step, consider contacting support or a qualified technician.
Parts You May Need
Upstream O2 sensor (Bank 1 Sensor 1)
O2 sensor wiring pigtail
Exhaust manifold gasket
Anti-seize compound for sensor threads
Related Error Codes
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