Diagnostic Procedures

2000 Chevrolet Cavalier Base, 2D Coupe, Automatic, 4T40E/MN4SECTION Diagnostic Procedures
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  . After performing OBD system check, go to next step.
  2. If other DTCs are present, diagnose affected DTC(s). If no other DTCs are present, go to next step.
  3. Check fuel level in tank. Add fuel as necessary. If fuel level was low (almost empty), go to step  5 . If fuel level was okay, go to next step.
  4. Start engine. Ensure coolant temperature is 167-203°F (75-95°C). Raise engine speed to 1200 RPM. Using scan tool, observe O2S 1 voltage. Voltage should vary within a range of 100-900 mV. Occasionally voltage should increase by greater than 447 mV (during power enrichment mode). If voltage is as specified, go to BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article. If voltage is not as specified, go to DTC P0134: O2S CIRCUIT-INSUFFICIENT ACTIVITY-SENSOR 1 (2.2L "J" BODY)  or DTC P0134: O2S CIRCUIT-INSUFFICIENT ACTIVITY-SENSOR 1 (2.4L "J" & "N" BODIES)  diagnosis.
  5. Using scan tool, select CLEAR INFO or CLEAR DTCs function to clear DTCs. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Operate vehicle within conditions required for setting this DTC. Select SPECIFIC DTC function then enter this DTC. If scan tool indicates TEST RAN AND PASSED, go to next step. If scan tool does not indicate TEST RAN AND PASSED, repeat step  2 .
  6. If any other DTCs are set, diagnose DTCs as necessary. If no other DTCs are set, system is okay. See DIAGNOSTIC AIDS  .
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When to See a Mechanic

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

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