Diagnostic Procedures

1999 Chevrolet Cavalier Z24, 2D Convertible, AutomaticSECTION Diagnostic Procedures
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step.
  2. Check for possible cause of Electromagnetic Interference (EMI), such as spark plug wires routed too close to IC module, high power transmitters operating within vicinity or the use of a battery charger. If possible source of EMI is found, remove source. If EMI interference is not noticed, go to next step.
  3. Clear DTCs and retest. If DTC P0371 resets, go to next step. If DTC P0371 does not reset, fault is not present.
  4. Check terminal contact of 24X spark reference circuit at IC module and PCM harness connector. Repair as necessary. If terminal contact is okay, go to next step.
  5. Replace IC module.
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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.