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

Fig 2: Code 23 Flow Chart (2.5L & 4.3L Turbo) MAT Sensor Temperature Low