Diagnostic Aids

1992 GMC Magnavan 5.7 KSECTION Diagnostic Aids

If the engine is allowed to cool overnight, the coolant and MAT sensors should read close to each other, when measured with a Scan tester. A Code 23 will also result if signal and ground circuits become open.

CODE 23 ECM TERMINAL & CIRCUIT WIRING ID (2.5L)

Application ECM Terminal Wire Color
Signal C12 Tan
MAT Ground D2 Black/Red
CODE 23 ECM TERMINAL & CIRCUIT WIRING ID (4.3L TURBO)

Application ECM Terminal Wire Color
Signal GF16 Tan
MAT Ground BB5 Black
TEMPERATURE-TO-RESISTANCE VALUES(1)(2)

°F (°C) Ohms
210 (100) 185
160 (70) 450
100 (38) 1800
70 (20) 3400
40 (4) 7500
20 (-7) 13,500
0 (-18) 25,000
-40 (-40) 100,700
(1) Measure resistance across sensor terminals.
(2) Temperatures are approximates.
Fig 1: Code 23 Schematic (2.5L & 4.3L Turbo) MAT Sensor Temperature Low
G91E07386
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.