What does it mean?
This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to OBD-II equipped vehicles. Although generic, specific repair steps may vary by make/model.
The EGR (exhaust gas recirculation) system is designed to lower combustion temperatures under certain conditions, thereby reducing nitrogen oxide (NOx) emissions. It does this by recirculating inert exhaust gases into the cylinder to burn with the air/fuel mixture. Inert exhaust gases burn slower and lower combustion temperatures. The EGR valve is computer-controlled and opens to allow exhaust gases to flow into the cylinders.
The EGR valve may be vacuum-operated. If so, a PCM-controlled EGR vacuum solenoid is used to provide vacuum to the EGR valve. When activated by the PCM, the EGR solenoid opens, allowing engine vacuum to move to the EGR valve. This engine vacuum opens the valve, allowing exhaust gases to pass through and enter the combustion chamber. Other EGR valves are electronic and directly controlled by the PCM. The PCM will activate the solenoid(s) that are integral to the EGR valve. These solenoids will open for varying durations, allowing exhaust to pass as needed. The EGR system is continuously monitored for faults. A feedback sensor on most EGR valves informs the computer of the actual EGR position. This sensor typically ranges between 0.4 and 5 volts.
If this EGR position sensor has an abnormally high reading for too long, this code may be set. Consult a vehicle-specific repair manual for your “C” circuit location.
Related EGR sensor “C” fault codes:
P044A Exhaust Gas Recirculation Sensor “C” Circuit
P044B Exhaust Gas Recirculation Sensor “C” Circuit Range/Performance
P044C Exhaust Gas Recirculation Sensor “C” Circuit Low
P044E Exhaust Gas Recirculation Sensor “C” Circuit Intermittent/Erratic
Symptoms
Symptoms of a P044D DTC may include:
Increased combustion temperatures (and NOx emissions)
MIL (Malfunction Indicator Lamp) illumination
Possible surging while driving
Possible intermittent stalling
Causes
Potential causes
of a P044D code include:
EGR sensor signal circuit shorted to B+ (battery voltage)
EGR sensor signal circuit shorted to 5-volt reference circuit at EGR
EGR sensor ground circuit open
EGR sensor signal circuit open
Faulty EGR (internal EGR sensor or solenoid failure)
Debris stuck in valve holding it open or closed
Possible Solutions
If the vehicle starts and stalls or won’t run with this code present, try disconnecting the EGR valve then restarting. If this makes no difference, remove the EGR valve and inspect for debris. Clean and reinstall. If this still doesn’t resolve the issue, block off the EGR port and try starting the engine. If this allows the engine to start, the EGR valve is stuck open and needs replacement. If disconnecting the PCM-controlled EGR valve allowed the engine to restart, there’s likely a wiring issue, possibly a short circuit holding a solenoid open.
Using a scan tool, view the EGR position on the data stream with the key on engine running and compare with desired EGR position. If it appears normal, suspect an intermittent problem. If it displays 5 volts or more, check the EGR sensor signal circuit for a short to the 5-volt reference wire or to B+. Repair as needed. Also verify there’s a good ground path on the ground circuit. Repair any open or short on the ground circuit.
On a vacuum-controlled EGR valve with an EGR solenoid: if disconnecting the vacuum source from the EGR valve allows the engine to start, suspect a faulty EGR solenoid allowing vacuum to the EGR valve constantly. Replace the EGR solenoid as needed. If this code is present and your engine starts and runs fine, suspect an open in the wiring. Inspect and repair any wiring issues. If wiring checks out, replace the EGR valve. If the wiring to and from the EGR valve