Diagnostic Aids

1987 Chevrolet Hi-Cube 6.2 J, 475/M40SECTION Diagnostic Aids
WARNING: This page does not describe the selected car, but rather 18 other vehicles, including the 1994 GMC Vandura Special, 1994 GMC Vandura, 1994 GMC Suburban, 1994 GMC Rally Camper Special, and 1994 GMC Rally. However, it is still accessible from the selected car via links, so may be relevant.

Verify a clean, tight connection for the sensor ground. An open circuit at sensor signal terminal or ground terminal will result in a Code 13.

CODE 13 TERMINAL & CIRCUIT WIRING IDENTIFICATION

Application PCM Terminal Wire Color
"C" & "K" Series
7.4L
Oxygen Sensor Signal A10 Purple
Oxygen Sensor Ground A12 Tan
"G" Series
7.4L A/T
Oxygen Sensor Signal A10 Purple
Oxygen Sensor Ground A12 Tan
"P" Series
7.4L A/T
Oxygen Sensor Signal A10 Purple
Oxygen Sensor Ground A12 Tan
Fig 1: Code 13 Schematic (7.4L) Open Oxygen Sensor Circuit
G91H07378
RENDER: 1.0x

NO RELATED

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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.