Code 25, Mat Sensor Temp. Low - 4.3L Turbo

ECM supplies and monitors a voltage signal (4-6 volts) to sensor. When temperatures are low, sensor resistance is high and ECM will see a high-monitored voltage signal. As temperature increases, sensor resistance decreases and voltage sensed by ECM drops.

NOTE: Test numbers refer to test numbers on diagnostic chart.

A scan tester cannot be used to diagnose this fault due to the ECM transmitting a default value when code is set. If voltage is greater than 4 volts, wiring and ECM are okay.
If resistance is less than 100 ohms, replace sensor.

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, MAT Sensor Temp Low (4.3L Turbo)

Fig 2: CODE 25, Flowchart, MAT Sensor Temp. Low (4.3L Turbo)