P1408 Code: Meaning, Causes, and Symptoms | OBD2 Codes
P1408 – EGR Flow Out Of Self Test Range
P1408 Possible Symptoms
Engine Light ON (or Service Engine Soon Warning Light)
P1408 Possible Causes
Faulty Exhaust Gas Recirculation (EGR) Valve,Exhaust Gas Recirculation (EGR) Valve Vacuum hose off or defective,Plugged Exhaust Gas Recirculation (EGR) Valve
The Exhaust Gas Recirculation (EGR) system recirculates a portion of the exhaust gasses into the intake manifold under average vehicle driving conditions to reduce combustion temperatures and exhaust gas NOx content. The amount of exhaust gas recirculated varies from zero with a cold engine to a fixed rate for a hot engine with intermediate load and low engine speed. This test is performed during the Key On Engine Running (KOER) on demand self-test only. The EGR system is commanded ON at a fixed engine speed. The test fails and the Diagnostic Trouble Code (DTC) is output when the measured EGR flow falls above or below the required calibration.