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HOMESERVICE MANUALSCHEVROLET1985SUBURBAN C10, 6.2 CREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMDIESEL CEC TESTS W/CODESDDC TESTER CHECK
1985 Chevrolet Suburban C10, 6.2 C

DDC Tester Check

1985 Chevrolet Suburban C10, 6.2 CSECTION DDC Tester Check

The Diesel Diagnostic Check (DDC) Tester (J-34750) is used to check the ECM's ability to detect a fault and set a trouble code. The mode selector assists diagnostics if no code is set.

This test verifies that the DDC tester is operating properly.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).
  1. Checks to see if tester is supplied with 12 volts, and if ALCL circuit is grounded or faulty. Normally, when connection is made to ALCL, the Check Engine light (CEL) in the tester should glow.
  2. When ignition is turned "on", the CEL should remain on. If CEL goes off, ECM may be shorted internally.
NOTE: When using the DDC tester in any diagnostic mode (3.9K or 10K), the CEL will flicker. This is normal. When switching from a diagnostic mode to Normal or Ground, the CEL will glow steadily for 10 seconds, then go off. This is the normal ECM reset time.
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.