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.

Fig 1: Code 23, MAT Sensor Temp. Low Troubleshooting Chart (1991 2.5L & 4.3L Turbo)

Courtesy of GENERAL MOTORS CORP.

TEMPERATURE-TO-RESISTANCE VALUES

°F (°C) ⁽¹⁾

⁽²⁾ Ohms

210 (100)

185

160 (70)

450

100 (38)

1,800

70 (20)

3,400

40 (4)

7,500

20 (-7)

13,500

0 (-18)

25,000

-40 (-40)

100,700

⁽¹⁾	Temperatures are approximate.

⁽²⁾	Measure resistance across sensor terminals.