P1400: How to Diagnose & Fix — EGR / DPFE Sensor Circuit Low Voltage (manufacturer-specific)
4 vehicles · 2 makes · $50-$2,500 repair
How to diagnose and fix P1400: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Ford F-150 · 1997–2004
The Delta Pressure Feedback EGR (DPFE) sensor and the EGR throttle-body spacer passages are a chronic Check-Engine source on 1997-2004 4.2L/4.6L/5.4L trucks. The ceramic DPFE sensor drifts or cracks, and the narrow 90-degree EGR elbow passages carbon up until flow is blocked, setting P0401 (insufficient EGR flow). The result is a rough idle, stumble or stall when coming to a stop, hesitation, and reduced fuel economy. It is frequently misdiagnosed as the EGR valve itself.
Common Symptoms
- Check-engine light with P0401/P0402
- Rough idle and stumble at stops
- Stalling when decelerating to a stop
- Hesitation on light acceleration
- Reduced fuel economy
How to Fix
Test the DPFE sensor voltage and manually apply vacuum to the EGR valve at idle to confirm the valve/passages are clear. Replace the DPFE sensor (inexpensive, ~15-minute job) and clean the carbon-clogged EGR tube/throttle-body spacer passages. Replace cracked vacuum lines and the EGR valve only if proven faulty.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- DPFE / EGR Pressure Feedback Sensor (bolt-mount design)OEMF77Z-9J460-AB (Motorcraft DPFE-15)Cross-refStandard Motor Products VP8, Standard Motor Products VP8T, Wells 5S2049$25–$65
Motorcraft DPFE-15 (Ford F77Z-9J460-AB) is the updated Motorola 1.0-volt silicon design that supersedes the original ceramic sensor, and RockAuto lists it for every engine
- DPFE / EGR Pressure Feedback Sensor (clip-mount design)Cross-refStandard Motor Products VP17, Wells 5S2047, NTK EA0008$22–$32
RockAuto explicitly splits these listings by mounting and by engine VIN: Wells 5S2047 and NTK EA0008 are called out as 'Engine VIN W; clip mount' on the 4.6L, while 5S2049/EA0009 are 'Engine VIN 6 or VIN W; bolt mount'.
Sources for this issue (1)
Ford Freestar · 2004–2007
The Freestar uses Ford's differential pressure feedback EGR system, and it fails in a well-known pattern. The DPFE (EGR pressure feedback) sensor loses accuracy when its diaphragm weakens or moisture contaminates it, so the PCM commands more vacuum to the EGR valve and the engine runs poorly. Separately, the EGR passages under the plastic upper intake carbon up and physically restrict flow. The original DPFE hoses are a high-temperature type that crack or collapse internally from thermal cycling, which produces the same code. Because there are three independent causes, owners commonly replace one part, clear P0401, and have it return within weeks — this is the single most repeated repair loop on these vans.
Common Symptoms
- Check engine light with P0401
- Rough idle or stumble at light throttle
- Hesitation on acceleration
- Failed state emissions test
- Repeat return of the same code after a sensor replacement
How to Fix
Test DPFE voltage, inspect both high-temperature hoses, test the EVR solenoid and clean the intake EGR passages before ordering. The exact sensor, regulator and hose branches could not all be verified as a current purchasable fitment set, so no partial parts-swap link is approved.
Sources for this issue (3)
Porsche Macan · 2014–2018
The EU-market Macan S Diesel (3.0 V6 TDI) is prone to EGR valve faults and diesel particulate filter (DPF) clogging, especially on cars used for short urban journeys that never complete a hot regeneration. EGR electrical faults can also block regen from running, compounding soot buildup. Additionally, the AdBlue (SCR) pipework at the rear of the engine bay splits, leaving crystallized AdBlue residue around the connectors and triggering emissions warnings. These are highly relevant to German/EU diesel owners; this engine was not sold in the US.
Common Symptoms
- DPF / exhaust emissions warning light
- Repeated/failed regeneration cycles
- Reduced power / limp mode
- AdBlue (DEF) warning or low-range message
- Crystallized AdBlue residue at rear of engine bay
- EGR fault warning
How to Fix
Force/complete a DPF regeneration with a sustained ~20-minute high-rpm drive; clean or replace the EGR valve; replace cracked AdBlue lines/connectors and top up DEF. Severe DPF clogging requires forced regen, off-car DPF cleaning, or DPF replacement. Address EGR fault codes promptly so regen can complete. Avoid chronic short-trip use.
Sources for this issue (3)
Ford Crown Victoria · 1996–2011
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P1400 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P1400 mean?
P1400 stands for "EGR / DPFE Sensor Circuit Low Voltage (manufacturer-specific)." P1xxx codes are manufacturer-defined, so confirm P1400 against your specific brand before buying parts. On Ford — the best-documented version — it is DPFE (Differential Pressure Feedback EGR) sensor circuit low voltage: the PCM saw an out-of-range low signal from the sensor that measures EGR flow. Volkswagen/Audi use P1400 for an EGR valve circuit electrical fault, GM uses it for the cold start emission reduction control system, and Subaru for a fuel tank pressure control solenoid valve circuit fault. In each case it is an emissions fault: the check engine light comes on, the vehicle will fail an emissions test, and you may notice rough idle, pinging, or slightly reduced fuel economy.
What are the most common causes of P1400?
The most common causes of P1400 are: Failed DPFE / EGR pressure feedback sensor (Ford), Cracked, collapsed, melted, or disconnected rubber hoses between the EGR tube and the DPFE sensor, Clogged EGR passages or a carbon-fouled EGR valve, Open, shorted, or corroded wiring/connector in the sensor or EGR solenoid circuit (VW/Audi: EGR valve circuit electrical fault), Failed EGR vacuum regulator solenoid, Failed PCM/ECU driver circuit (rare — verify everything else first). The specific cause varies by vehicle.
How much does it cost to fix P1400?
Repair costs for P1400 range from $50 to $2,500, depending on the vehicle and root cause.
Which vehicles are affected by P1400?
Au7o has documented P1400 across 4 vehicle models from 2 manufacturers: Ford, Porsche.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.