With PFI

Code 23 Chart:

Code 23 Wiring Diagram:

CIRCUIT DESCRIPTION:

The Manifold Air Temperature (MAT) Sensor uses a thermistor to control the signal voltage to the Electronic Control Module (ECM). The ECM applies a voltage (about 5 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.

NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to ECM CONNECTOR IDENTIFICATION under ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS for correct color code identification of circuit.



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

Code 23 will set if:

^ A signal voltage indicates a manifold air temperature below -30~C (-22~F).

^ Boost conditions have present for longer than 10 seconds.

^ Due to the conditions necessary to set code 23, the "SERVICE ENGINE SOON " light will only stay "ON" while the fault is present.

1. A "Scan Tool" may not be used to diagnose this fault, due the ECM transmitting "default" (substitute) values while the fault is present. A code 23 will set due to an open sensor, wire or connection. This test will determine if the wiring and ECM are OK.

2. If the resistance is greater than 25,000 ohms, replace the sensor.