Circuit Description

2000 Chevrolet Chevy Express G3500, Van Cargo, 4.3 WSECTION Circuit Description
NOTE: For circuit reference, see appropriate SYSTEM WIRING DIAGRAMS article.

VCM supplies a voltage of about.45 volt between HO2S signal and HO2S ground circuits. HO2S varies voltage from about one volt with rich exhaust to.1 volt with lean exhaust. HO2S produces no voltage and acts as an open circuit when temperature is less than 600Β°F (316Β°C). An open sensor circuit or a cold sensor causes open loop operation.

HO2S heater provides for faster sensor warm-up allowing sensor to become active in a shorter period of time and remain active during long extended idle. DTC determines if HO2S or HO2S circuit is open. DTC P0134 will set if VCM fails to detect minimum number of HO2S 1 voltage transitions greater than and less than bias voltage range of 300-600 mV.

For duplication of DTC, ensure:

  • DTC P0135 is not set.
  • No active EVAP system, misfire, TP, IAT, MAP, ECT or MAF sensor DTCs are set.
  • No intrusive tests are in progress.
  • No device controls are active.
  • System voltage is 11.7-18 volts.
  • Engine run time is greater than 2 minutes.
  • Decel fuel cut-off mode is not active.
  • ECT is 137Β°F (58.5Β°C) or greater.
  • MAF is 13 grams per second.
  • System is in closed loop.

RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.