Diesel Trouble Codes

P0404 — Exhaust Gas Recirculation Control Circuit Range/Performance (6.7 Cummins (EGR + DPF, pre-SCR))

Exhaust Gas Recirculation Control Circuit Range/Performance

Updated September 2, 2026

What it means

The engine control module has detected that the exhaust gas recirculation control circuit is operating outside its expected range or performance.1

Most likely causes

  1. EGR valve position feedback / control circuit fault — EGR valve position sensor or control circuit signal out of expected range; valve may be sticking or electrically degraded.1
  2. EGR valve mechanically stuck or binding — Carbon buildup or mechanical binding causes actual valve position to diverge from commanded position, triggering range/performance detection.1
  3. EGR control wiring / connector issue — Chafed, corroded, or loose wiring/connector to the EGR valve/position sensor produces erratic circuit readings.1
  4. EGR cooler flow restriction affecting valve operation — Restricted EGR cooler flow can alter EGR system performance and cause range/performance faults.1

How to diagnose

  1. Verify freeze frame and repeatability of P0404 under normal operating conditions.
  2. Inspect EGR valve electrical connector and wiring for corrosion, chafing, or loose pins; check reference/return voltages per service data.
  3. Command EGR valve position with scan tool and monitor actual vs commanded position feedback; note range/performance deviation.
  4. Inspect EGR valve and passages for carbon buildup, sticking, or binding; check valve pintle movement and freedom of travel.
  5. Check EGR cooler for restriction or internal blockage that alters flow characteristics.
  6. Review related EGR codes such as P0401 flow insufficient, P0402 flow excessive, P042E stuck open for pattern clues.
  7. Clear codes, perform a controlled road test with EGR monitoring to confirm circuit returns to expected range.

Parts and tools you may need

Rough cost and difficulty

Cost varies by root cause; electrical/wiring repairs are typically lower cost than EGR valve or cooler replacement. Diagnosis labor is required before parts replacement.

When to see a pro

If EGR valve replacement or EGR cooler service is needed, or if wiring faults require harness repair, have a qualified diesel technician perform the work. Do not attempt high-pressure fuel system service. Seek professional help for persistent range/performance faults after basic checks.

Sources

  1. Curated DTC seed — 6.7 Cummins (EGR + DPF, pre-SCR) (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎