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2012 MERCEDES-BENZ ML
3.5L V6•AWD•AUTOMATIC•gas•M272
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Repairs0Labor492Torque2165Fluid8DTC1852Battery2Maintenance0Recalls0
P1130moderate severityPowertrain

HO2S Circuit Low Variance Bank 1 Sensor 1

on 2012 Mercedes-Benz ML 3.5L V6 · AWD

What this code means

The ECU detected that the upstream O2 sensor on Bank 1 is showing insufficient voltage switching (low variance). The sensor is not oscillating between rich and lean as expected during closed-loop operation.

Symptoms

  • Check Engine Light
  • Poor fuel economy
  • Failed emissions test
  • Slightly rough idle

Common causes

  • Aging O2 sensor with slow response
  • Exhaust leak before O2 sensor
  • Fuel system issue masking sensor response
  • Contaminated O2 sensor tip
  • Wiring resistance issue

Diagnostic steps

  1. Monitor O2 sensor switching rate with scan tool
  2. Check for exhaust leaks at manifold
  3. Test sensor response to induced rich/lean condition
  4. Inspect sensor for contamination
  5. Check sensor wiring resistance

Repair notes

Replace the upstream O2 sensor on Bank 1 if response time has degraded.

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