Diagnostic Aids

1995 Chevrolet Forward Control 4.3 Z, AutomaticSECTION Diagnostic Aids

Scan tester displays transmission fluid temperature in degrees Centigrade. After transmission is running, displayed temperature should rise steadily to about 100°C then stabilize. A faulty connection or an open in ground circuit or signal circuit will result in a Code 59. 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 firm shifts or TCC enabled complaint. If code is intermittent, see INTERMITTENTS in TESTS W/O CODES - GASOLINE article.

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

Temperature: °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 59 Schematic ("C", "K" & "P" Series) Transmission Fluid Temperature Low
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.