Diagnostic Aids

1995 GMC Forward Control 4.3 Z, StandardSECTION Diagnostic Aids

Check harness routing for a potential short to ground in signal circuit. Scan tester displays transmission fluid temperature in degrees Centigrade. After transmission is running, temperature display should rise steadily to about 100°C then stabilize. Test transmission sensor at various temperature levels to determine if sensor is out of calibration. See TRANSMISSION SENSOR - TEMP TO RESISTANCE chart. An out-of-calibration sensor could result in delayed shifts or TCC enabled complaint.

TEMPERATURE-TO-RESISTANCE VALUES (1)(2)

°F (°C) Ohms
150 (66) 42-56
100 (38) 159-198
70 (20) 420-514
40 (4) 1308-1609
20 (-7) 3088-3941
0 (-18) 7902-10,943
-40 (-40) 73,556-127,857
(1) Measure resistance across sensor terminals.
(2) Temperatures are approximates.
Fig 1: Code 79 Schematic ("C", "K" & "P" Series) Transmission Fluid Temperature High
G95I28058
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:

  • 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.