DTC 23

Code 23 - Manifold Air Temp. (MAT) Sensor:

Wiring Diagram for Manifold Air Temp. (MAT) Sensor:

CODE 23 - MANIFOLD AIR TEMPERATURE SENSOR CIRCUIT (MAT) LOW TEMPERATURE INDICATED

Circuit Description:


The MAT sensor uses a thermistor to control the signal voltage to the ECM. The ECM applies a voltage (4-6 volts) on CKT 472 to the sensor. When the air is cold the sensor (thermistor) resistance is high, therefore the ECM will see a high signal voltage. If the air is warm the sensor resistance is low therefore the ECM will see a low voltage.

A "Scan" tool reads temperature of the air entering the engine should read close to ambient air temperature when engine is cold, and rises as underhood temperature increases.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 23 will set if:

^ A signal voltage indicates a manifold air temperature below - 30~C for 3 seconds.

^ Time since engine start is 8 minutes or longer

^ No VSS Due to the conditions necessary to set a Code 23, the "Service Engine Soon" light will only stay "ON" when all three conditions are met.


2. A Code 23 will set, due to an open sensor wire, or connection. This test will determine if the wiring and ECM are OK.

3. This test will determine if CKT 472 is open.