## Diesel Engine Management System

#### DTC Troubleshooting (cont'd)

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DTC P0112: IAT Sensor Circuit Low Voltage

1. Check the ''On Board Diagnostic (OBD) System Check''.

Was the ''OBD System Check'' performed?

YES – Go to step 2.

NO – Go to OBD System Check.

1. Turn the ignition switch ON (II).

1. Check the IAT with the scan tool.

Is there more than 120°C (248°F)?

YES – Go to step 4.

NO – Go to step 9.

1. Disconnect the IAT sensor 5P connector.

1. Check the IAT with the scan tool.

Is about 215°C (419°F) indicated?

YES – Replace the IAT/MAF sensor.

NO – Go to step 6.

1. Turn the ignition switch OFF.

1. Disconnect ECM connector.

1. Check the IAT sensor signal circuit for a short to ground.

Is a problem found?

YES – Repair the IAT signal circuit.

NO – Substitute a known-good ECM and recheck. If symptom/indication goes away, replace the original ECM.

1. Check the temperature reading on the scan tool. Be aware that if the engine is warm, the reading will be higher than the ambient temperature. If the engine is cold, the IAT and ECT will have the same value.

Is the correct ambient temperature indicated?

YES – Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the IAT sensor and at the ECM.

NO – Replace the MAF/IAT sensor.

NOTICE

The battery power supply short circuit to 5 V power supply damages the ECM.

a a a