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HOMESERVICE MANUALSCHEVROLET1993SPORTVAN G20, 5.7 KREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - TESTS W/CODES - DIESELDIAGNOSTIC CHARTSDIAGNOSTIC SYSTEM CHECK (WITH AUTOMATIC TRANSMISSION)
1993 Chevrolet Sportvan G20, 5.7 K

Diagnostic System Check (With Automatic Transmission)

1993 Chevrolet Sportvan G20, 5.7 KSECTION Diagnostic System Check (With Automatic Transmission)

The diagnostic system check is an organized approach to identifying a problem created by a control module system malfunction. This is the starting point for any driveability complaint diagnosis, as it directs technician to the next logical step in diagnosis, helps reduce diagnostic time and prevents the unnecessary replacement of good parts.

NOTE: Test numbers refer to numbers on diagnostic chart.
  1. This tests MIL operation. With ignition on and engine off, light should be on.
  2. No MIL at this point indicates there is a problem with MIL control circuit or ECM control of that circuit.
  3. This tests ability of ECM to control MIL light. With diagnostic terminal grounded, MIL should flash DTC 12 three times, followed by any other DTC stored in memory. A ECM or PROM error may result in the inability to flash DTC 12.
  4. Use TECH 1 to aid in diagnosis (to check if serial data is available). If a PROM error is present, the ECM may have been able to flash DTC 12 or 15, but not enable serial data.
  5. This step will isolate if customer complaint is an MIL or driveability problem with no MIL displayed. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION table under TROUBLE CODE IDENTIFICATION , to determine if code is valid. An invalid DTC may be the result of a faulty scan tester, PROM or ECM.
  6. If all scan data values are okay, check engine mechanical condition.
Fig 1: Schematic, Diag. System Check A/T ("C" & "K" Series)
G93F76575Courtesy of GENERAL MOTORS CORP.
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:

  • • 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.