16785/P0401/001025

16785/P0401 - Exhaust Gas Recirculation Flow Insufficient Detected

Possible Symptoms

• Drivebility problems (check dtc's with Knock Sensor)
• Irregular behaviour

Possible Causes

• EGR valve stuck closed
• EGR valve leaks vacuum
• EGR flow restricted
• Circuit EGR short to B+
• EGR damaged
• Circuit DPF EGR sensor (differential pressure) disconnected, short to B+ or Ground
• DPF EGR sensor downstream hose off or plugded
• DPF EGR sensor damaged, wrong attached
• Control Module damaged

Possible Solutions

• Check all wiring and connections to and from EGR and DPF-EGR
• Check the EGR: use a vacuumpump and pull open the EGR: rpm should change
• Clean the EGR
• Check / Replace EGR
• Check / Replace DPF-EGR

Special Notes

• The EGR system is monitored when driving at steady state and the EGR is commanded on. When the DPF-EGR sensor indicates that EGR flow is less then a desired minimum a dtc is set.
• N.B. mechanics with less knowledge do exchange the EGR often, but 75% sure the problem will be back (probably the DPF-EGR sensor causes the problem).