Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 25 other vehicles, including the 1992 Oldsmobile Bravada, 1992 GMC Vandura Special, 1992 GMC Vandura, 1992 GMC Value Van, and 1992 GMC Sonoma. However, it is still accessible from the selected car via links, so may be relevant.

If the engine is allowed to cool overnight, the coolant temperature sensor and MAT sensor should read close to each other, when measured with a Scan tester. A Code 25 will also result if sensor signal circuit is shorted to ground.

CODE 25 ECM TERMINAL & CIRCUIT WIRING ID (2.5L)

Application	ECM Terminal	Wire Color
Signal	C12	Tan
MAT Ground	D2	Black/Red

CODE 25 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 25 Schematic (2.5L & 4.3L Turbo) MAT Sensor Temperature High

Fig 2: Code 25 Flow Chart (2.5L & 4.3L Turbo) MAT Sensor Temperature High