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Home >> Chevrolet >> 1994 >> Forward Control 7.4 N >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 6.5L Diesel >> Self-Diagnostic System >> Diagnostic Procedure >> Diagnostic Procedure

Diagnostic Procedure

  1. Ensure all engine systems NOT related to the Diesel Electronic Control (DEC) system are operating properly. DO NOT  proceed with testing unless all non-DEC system problems are repaired.
  2. ALWAYS begin diagnosis with diagnostic system check to determine if DEC system and PCM are working properly. See DIAGNOSTIC SYSTEM CHECK  chart. If trouble codes, other than Diagnostic Trouble Code (DTC) 12 are displayed, determine if they are hard or intermittent trouble codes.
  3. A hard code is present while working on vehicle, and problem condition persists. Hard codes will cause Malfunction Indicator Light (MIL) to come on.
    NOTE: SERVICE ENGINE SOON light, located on instrument cluster, is also referred to as the Malfunction Indicator Light (MIL).
  4. An intermittent code does not reset itself and is NOT present while working on vehicle. Intermittent codes are often caused by loose connections. MIL will go out 10 seconds after fault goes away. For intermittent diagnostic procedures, proceed to TESTS W/O CODES - 6.5L DIESEL article in this section.
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