P0400 — Exhaust Gas Recirculation Flow Malfunction
Category: Powertrain Severity: Medium
Updated:
DTC code P0400 means: Exhaust Gas Recirculation Flow Malfunction. It falls under the "Powertrain" category, with an estimated severity of Medium. Common causes include eGR valve clogged with carbon, clogged EGR passages and failed EGR control solenoid; it's worth confirming the diagnosis before replacing parts.
Possible causes
- EGR valve clogged with carbon
- Clogged EGR passages
- Failed EGR control solenoid
- Faulty EGR position or DPFE sensor
Symptoms
- Stumbling at low rpm
- Rough idle
- Pinging on acceleration
- Check engine light
How to diagnose it step by step
- Command the EGR with a scan tool and watch idle.
- Remove and clean the valve.
- Clean the passages.
- Test the position/DPFE sensor.
- Replace the valve if damaged.
How to fix it
Remove and clean the EGR valve and passages. If it still fails, check the actuator and the position or differential-pressure sensor.
Estimated repair cost
Cleaning: $100–250. New EGR valve: $200–650.
Frequently asked questions
What does DTC code P0400 mean?
Exhaust Gas Recirculation Flow Malfunction.
Is code P0400 serious?
Severity Medium. Not urgent, but worth diagnosing to avoid bigger damage.
Can I keep driving with code P0400?
Yes, you can drive; fix it to avoid pinging and high emissions.
Related codes
P0401 P0402 P0403 P0404 P0405 P0406 P0410 P0411 P0420 P0421
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