DTC 23

DTC 23 Circuit Diagram:

DTC 23 Diagnostic Chart Low Temp Indicated In MAT Circuit:

CIRCUIT DESCRIPTION:

The Manifold Air Temperature (MAT) sensor uses a thermistor to control the signal voltage to the ECM. The ECM applies a voltage (4-6V) through BLU/BLK wire to the sensor. When manifold air is cold, the sensor (thermistor) resistance is high, therefore, the ECM will see a high signal voltage. As the air warms, the sensor resistance becomes less, and the voltage drops.

TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.

1. This step checks to see if Code 23 is the result of a hard failure or an intermittent condition. A Code 23 will set if:

a. Engine has been running for longer than 60 seconds.
b. Signal voltage indicates an MAT temperature less than -38°C.

2. This test simulates conditions for a Code 25 (High Temperature Indicated). If the Scan tool displays a high temperature, the ECM and wiring are OK.

3. This step checks continuity of BLU/BLK wire and BLK/WHT wire. If BLU/BLK is open, there may also be a Code 25.

DIAGNOSTIC AIDS:

If the engine has been allowed to cool to an ambient temperature (overnight), coolant and MAT temperatures may be checked with a Scan tool and should read close to each other. A Code 23 will result if BLU/BLK wire and BLK/WHT wire become open. If Code 23 is intermittent,
Intermittant Check Procedure