Technical Description of OBD-II Trouble Code
The Exhaust Gas Recirculation Sensor C Circuit is registering a low voltage.
What does that mean?
This code is a generic powertrain code that applies to all vehicle makes and models from 1996 onwards. However, the specific repair steps may vary slightly depending on the model.
EGR systems have different designs, but they all function in a similar manner. The EGR valve is controlled by the PCM and allows a measured amount of exhaust gas to flow back into the cylinders to be burned with the air/fuel mixture. This helps to lower combustion temperatures and improve NOx emissions.
EGR is not necessary during cold startup or at idle. It is commanded on under certain conditions such as partial throttle or deceleration, depending on engine temperature and load. The EGR valve may be supplied with exhaust gas from an exhaust pipe or mounted directly in the exhaust manifold. When needed, the valve is commanded “on” to allow the gas to pass into the cylinders. Some systems divert the exhaust gas directly into the cylinders, while others inject it into the intake manifold where it is then pulled into the cylinders.
EGR systems can be either electrically controlled or vacuum controlled. Electrically controlled EGR valves are directly controlled by the PCM through a wiring harness. Vacuum controlled systems use a vacuum solenoid activated by the PCM to open the EGR valve. Both types of EGR valves may have an electrical connector for the feedback circuit, which allows the PCM to monitor the valve’s movement.
If the EGR “C” feedback circuit detects unusually low voltage or a lower position than commanded, the P044C code may be set. Refer to a vehicle-specific repair manual to locate the “C” sensor.
Related EGR sensor “C” trouble codes:
Symptoms
Symptoms of a P044C DTC may include:
Causes
Possible causes of a P044C code include:
Possible Solutions
If you have access to a scan tool, you can command the EGR valve to open. If it responds and the feedback indicates that the valve is moving properly, the problem may be intermittent. In cold weather, moisture can freeze in the valve and cause it to stick, but the problem may disappear as the vehicle warms up. Carbon or debris can also cause a valve to stick.
If the EGR valve does not respond to commands from the scan tool, disconnect the EGR harness connector. With the key in the on position and the engine off, use a voltmeter to check for 5 volts on the reference wire to the EGR valve. If there is no 5 volts, check if there is any voltage at all. If there is 12 volts, repair the short to voltage in the 5 volt reference circuit. If there is no voltage, connect a test light to battery voltage and probe the 5 volt reference wire. If the test light illuminates, the 5 volt reference circuit is shorted to ground. Repair as necessary. If the test light does not illuminate, check for an open in the 5 volt reference circuit. Repair as necessary.
If there is no apparent problem and there is no 5 volt reference, the PCM may be at fault, although other codes will likely be present. If 5 volts are present on the reference circuit, jumper the 5 volts to the EGR signal circuit. The scan tool should now read the EGR position as 100 percent. If it does not, connect a test light to battery voltage and probe the EGR signal circuit. If the test light illuminates, the signal circuit is shorted to ground. Repair as necessary. If the light does not illuminate, check for an open in the EGR signal circuit. Repair as necessary.
If, after jumpering the 5 volt reference circuit to the EGR signal circuit, the scan tool still does not read 100 percent for the EGR position, check for poor terminal tension at the EGR valve connector. If the wiring is okay, replace the EGR valve.
