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OBD-II Code

P1408

Severity

Not yet reviewed

Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.

Can you drive it

We cannot say

Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.

Indicative cost (USD)

$35–$450

From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.

P1408 indicates EGR Flow Out of Range — during a PCM-commanded EGR open event (typically at light cruise between 1,500 and 2,500 rpm with the engine warm), the DPFE sensor reported a pressure differential outside the expected window for the commanded EGR duty cycle.

How a shop works this

Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.

  1. Note every code that is set, not just this one.

    Codes that appear together usually narrow the cause faster than any one of them read alone.

  2. Read the freeze frame — the conditions the fault was recorded under.

    Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.

  3. Confirm the fault is current rather than history.

    Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.

  4. Then follow the diagnostic notes further down this page, in the order they are written.

    They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.

If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.

Common symptoms

  • Check engine light
Read the full diagnostic procedureP1408 indicates EGR Flow Out of Range — during a PCM-commanded EGR open event (typically at light cruise between 1,500 and 2,500 rpm with the engine…

P1408 indicates EGR Flow Out of Range — during a PCM-commanded EGR open event (typically at light cruise between 1,500 and 2,500 rpm with the engine warm), the DPFE sensor reported a pressure differential outside the expected window for the commanded EGR duty cycle. The PCM essentially said open the valve 30 percent and expected to see X mass flow; it saw Y, where Y is too far off to be a sensor error.

Cheapest-first ladder

  1. scan EGR_DC (duty cycle commanded) and DPFE voltage simultaneously and command an EGR open with the scan tool at warm idle — DPFE should rise from 1.0V at rest to 2.5V to 3.5V at 50 percent commanded flow; no rise means no flow.
  2. Disconnect the EGR vacuum line at the valve and apply 15 inches Hg with a hand pump — the engine should stumble immediately.
  3. Remove the EGR tube (two flare nuts) and inspect — a clogged tube is the most common root cause on Ford 3.0L Vulcan and 4.6L Modular engines.
  4. Verify EGR valve diaphragm holds vacuum for 30 seconds at 15 inches Hg; if it bleeds down, the valve diaphragm is torn.
  5. The expensive misdiagnosis is replacing the EGR valve when the steel EGR tube ($35 to $90) is the clogged component.
Vehicle-specific patterns2001-2007 Ford Taurus/Sable 3.0L Vulcan V6 is the textbook P1408 case — the EGR passages in the upper intake plenum clog with carbon by 100,000 miles.
  • 2001-2007Ford Taurus/Sable 3.0L Vulcan V6 is the textbook P1408 case — the EGR passages in the upper intake plenum clog with carbon by 100,000 miles.
  • 1997-2003Ford F-150 4.6L/5.4L 2V trucks suffer EGR tube blockage where the tube necks down before the EGR valve — physically punch through with a wire coat hanger and burn out remaining carbon.
  • 2000-2008Ford Ranger 3.0L Vulcan and 4.0L SOHC engines see P1408 chronically; the 3.0L responds well to a $60 EGR tube replacement, the 4.0L often needs the upper intake removed.
  • 1999-2003Ford Windstar 3.8L Essex sets P1408 when the EGR ports in the head crud over.

Estimated repair$35 to $450.

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