This diagnostic condition is typically Intake Air Temperature Sensor open circuit or short to power.
87.1.1
Intake Air Temperature Sensor Open Circuit/Short to Power Check
Check as follows:
1. Turn the ignition the ON (key On, engine OFF).
2. Check for multiple codes.
[a] If codes 1636/3, 2629/3 and 412/3 are active at the same time, go to step 3.
[b] If only fault 412/3 is active, disconnect the Intake Air Temperature Sensor and go to step 5.
3. Disconnect the Intake Air Temperature Sensor.
4. Measure the voltage between pin 1 of the Intake Air Temperature Sensor and ground.
[a] If the voltage is greater than 2.75 volts, repair the short to power between pin 52 of
the MCM 120–pin connector and the Intake Air Temperature Sensor, the Turbo
Compressor Out Sensor and the EGR Temperature Sensor.
[b] If no voltage is present on pin 1 of the Intake Air Temperature Sensor, repair the open
between pin 52 of the MCM 120–pin connector and the Intake Air Temperature
Sensor, the Turbo Compressor Out Sensor and the EGR Temperature Sensor.
5. Measure the resistance across pins 1 and 2 of the sensor (see Figure 87-1).
[a] If the resistance is greater than 4k Ω, replace the sensor.Refer to section 87.1.1.1.
[b] If the resistance is less than 4k Ω, go to step 6.
6. Turn the ignition switch to the ON position.
7. Measure the voltage between pins 1 and 2 of the IAT Senor harness connector.
[a] If the voltage is between 2.75 and 3.25 volts, refer to section 87.1.1.1.
[b] If the voltage is less than 2.75 volts, go to step 8.
8. Measure the voltage between pin 2 of the IAT Senor harness connector and ground.
[a] If the voltage is between 2.75 and 3.25 volts, repair the open circuit between pin 1
of the IAT Senor harness connector and pin 52 of the MCM 120–pin connector.
Refer to section 87.1.1.1.
[b] If the voltage is less than 2.75 volts, repair the open circuit between pin 2 of
the IAT Senor harness connector and pin 106 of the MCM 120–pin connector.
Refer to section 87.1.1.1.
