P1408
FordEGR Flow Out Of Self Test Range
The EGR system routes some exhaust gas back into the engine to help control emissions. During a self-test, the detected EGR flow response was outside the expected range; the code alone does not show whether flow was too low or too high, or identify a failed part. The check method and exact system components vary by model, year and engine. The warning light may be the only noticeable effect, though an EGR flow problem can also affect how the engine runs or its emissions.
⚠️ Before You Begin (Safety First)
This code alone does not usually mean the vehicle must be stopped immediately. If the engine stalls, runs severely rough, loses power, or the check-engine light flashes, stop somewhere safe and arrange an inspection. Avoid touching hot exhaust or engine components.
Common Symptoms
- The check-engine light may be on, with no noticeable change in how the vehicle drives.
- If EGR flow is insufficient or excessive, the engine may run unevenly, hesitate, or have other driveability changes; these symptoms are not specific to this code.
- Emissions may be affected if the EGR system is not operating as intended.
Common Causes
- Carbon or other deposits may restrict EGR passages and reduce flow.
- The EGR valve may stick, fail to move as commanded, or fail to seal correctly, causing flow outside the expected range.
- A flow-sensing component or its hoses, where fitted, may give an inaccurate signal or have a connection or leak problem.
- A fault in the EGR control, vacuum supply where used, wiring, or electrical connections may prevent the expected flow response.
- The code may be intermittent; additional codes and test results are needed to narrow down the cause.
Diagnostic Steps
- Record the code and note any other stored or pending codes before clearing anything; related codes can help direct diagnosis.
- With the engine off and cool, visually check accessible EGR-related wiring, connectors and hoses for disconnection, damage, cracking or obvious leaks. Do not pull on fragile hoses or wiring.
- Check whether the vehicle has noticeable rough running, hesitation or stalling, and note when it occurs; symptoms help distinguish an active driveability issue from a light-only condition.
- Do not replace the EGR valve or a sensor based on this code alone. Have the EGR flow response and related components tested using procedures for the vehicle's exact model, year and engine.
When to Call a Professional
Confirm the code and check for related codes before replacing parts. Use model-specific service information to compare EGR command with the system's flow feedback during the applicable test. Inspect the EGR valve, passages, control system, wiring and any flow-sensing components or hoses fitted to that vehicle. The self-test result indicates a detected condition, not proof that the valve or sensor needs replacement.
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Commonly Asked Questions
Does P1408 prove that the EGR valve is bad?
No. It reports that the EGR flow response was outside the self-test range. The valve, passages, control system, wiring, or flow feedback may need inspection before identifying a cause.
Does this code mean EGR flow is too low?
Not from this definition alone. It says the flow was outside the expected range, without specifying whether it was too low or too high.
Can I keep driving with P1408?
If the vehicle runs normally, this code alone does not necessarily require stopping immediately. Get it diagnosed; stop safely and seek help if the engine stalls, runs severely rough, loses power, or the check-engine light flashes.
Why might the vehicle have no symptoms?
The self-test can detect an out-of-range EGR response before the driver notices a change. The warning light may be the only obvious sign.
Browse Available Code Guides
Previous and next available guides in database record order, across makes. Adjacent entries may share a code number and do not necessarily describe related faults.