Diagnostic Procedure

1993 Chevrolet Sportvan G20, 5.7 KSECTION Diagnostic Procedure
  1. Ensure all engine systems not related to Diesel Electronic Control (DEC) system are operating properly. DO NOT  proceed with testing unless all problems not related to DEC system have been repaired. DEC system diagnosis should always begin with DIAGNOSTIC SYSTEM CHECK chart under DIAGNOSTIC CHARTS in TESTS W/CODES - DIESEL article in this section. Performing this check determines whether DEC system and ECM are working properly.
  2. If trouble codes (other than Code 12) are displayed, determine whether codes are hard or intermittent trouble codes. A hard code remains until code-setting condition is repaired. Hard codes cause Malfunction Indicator Light (MIL) to come on.
  3. An intermittent code does not reset itself and is not present when vehicle is repaired. An intermittent code is often caused by loose connections. MIL goes out 10 seconds after fault goes away.
Fig 1: Diesel Fuel Injection Diagnostic Circuit Schematic (A/T)
G93H76569Courtesy of GENERAL MOTORS CORP.
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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.