EGR Low Flow DTC P0401 - keywords 07 08 6.6 cool cooler diesel engine exhaust gas idle lmm recirculation restrict restriction soot valve

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

A dealer may encounter a customer concern of a SES light and a DTC P0401.

Complete the current SI diagnostics for any trouble code or symptom found. If diagnostics were inconclusive it is possible the vehicle has a restricted EGR cooler.

Vehicles that have extended idle times are more susceptible to restricted EGR coolers. Please question the customer about idle times. Also question the customer about how often they notice the Diesel Particulate Filter "Clean Filter Message."

If the customer has noticed the clean filter message on a regular basis, please direct them to the Diesel Supplement Owners Manual for "Diesel Particulate Filter" and the "Diesel Particulate Filter (DPF) System Description" found in SI.

Understanding the DPF system operation is extremely important.

Please document the DPF Regeneration data on the Repair Order.

Soot Mass:

Distance since last regeneration:

Engine run time since last regeneration:

DPF regenerations completed:

MAF at idle:

Reason for last regeneration:

If the vehicle has a P0401 and the customer does use the vehicle for extended idle times, the EGR cooler will have to be replaced.

Note: Using the Owners Manual Guidelines for driving the vehicle through a regeneration will help with the build up of soot.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.