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2009 GMC ENVOY
4.2L I6•4WD•AUTOMATIC•gas
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Repairs0Labor980Torque4001Fluid18DTC3918Battery2Maintenance0Recalls0
P1153moderate severityPowertrain

HO2S Insufficient Switching Bank 2 Sensor 1

on 2009 GMC Envoy 4.2L I6 · 4WD

What this code means

The PCM determined that the upstream O2 sensor on Bank 2 is not switching between rich and lean often enough during closed-loop operation. This is the Bank 2 counterpart to P1133 and the two codes are frequently seen together.

Symptoms

  • Check Engine Light
  • Poor fuel economy
  • Rough idle
  • Hesitation
  • Failed emissions test

Common causes

  • Faulty or lazy upstream O2 sensor Bank 2
  • Exhaust leak near sensor
  • Vacuum leak
  • Fuel delivery issue
  • MAF sensor contamination

Diagnostic steps

  1. Monitor O2 sensor switching rate with scan tool
  2. Check for exhaust leaks
  3. Perform vacuum leak test
  4. Test fuel pressure
  5. Clean or test MAF sensor

Repair notes

Replace upstream O2 sensor Bank 2. Check for exhaust leaks. Commonly appears alongside P1133.

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