P1406 — DPFE Circuit High Input

P1406 — DPFE Circuit High Input. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: control module driver fault, open or shorted wiring in the circuit, poor ground connection.

For Ford vehicles

differential pressure feedback sensor downstream hose off or plugged

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P1406 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the DPFE for damage, corrosion, chafing or poor contact.
Subsystem check With the DPFE disconnected, measure signal voltage at the harness connector: a high reading with the component unplugged indicates a short to power in the harness; if it drops to normal, the component itself is faulty.
Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P1406 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P1406 (parts and labor, USD, independent shop rates): Replace the faulty sensor or actuator: $150–$500; Control module repair: $300–$1,000; Repair wiring or connectors: $80–$250. Overall, fixing P1406 usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

How do I diagnose P1406 myself?

Start with a scan: confirm P1406, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the DPFE, and verify the suspect component against live data before buying parts.

How much does it cost to fix P1406?

Replace the faulty sensor or actuator — $150–$500; Control module repair — $300–$1,000; Repair wiring or connectors — $80–$250. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

What does OBD2 code P1406 mean?

Will P1406 clear itself?

Sometimes P1406 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What are the symptoms of P1406?

Drivers most often notice: possible limp mode depending on the affected component, Check Engine Light on, increased fuel consumption in some cases, the affected system operates intermittently or not at all.

When your check engine light comes on and a scan tool reveals code P1406, your vehicle's computer has detected a problem with the Differential Pressure Feedback EGR system, specifically a circuit input reading higher than it should. The Powertrain Control Module constantly monitors voltage levels throughout this emissions-related circuit, and P1406 triggers when it sees something pulling the signal line dangerously close to battery voltage — essentially the opposite of what it expects to find during normal operation.

The DPFE system measures exhaust gas recirculation flow using a sensor that monitors pressure differences across a metering orifice. Your engine control unit relies on this data to reduce combustion temperatures and cut harmful emissions. When the voltage on the DPFE signal circuit climbs abnormally high, the computer can't trust the readings anymore. It sets P1406 and often places the engine in a reduced-power mode to protect emission components and prevent potential damage. The fault typically accumulates over multiple drive cycles before illuminating the warning light permanently.

Diagnosing P1406 correctly requires understanding that "circuit high" points to three general possibilities: a power feed shorting into the signal wire, a broken ground path causing the circuit to float upward, or a failed component actively pulling the line high when it should be grounded or generating low-level feedback. Freeze frame data stored alongside the code gives you a snapshot of engine RPM, load, coolant temperature, and vehicle speed at the moment of failure — essential information for recreating the fault condition during testing.

Common Symptoms of P1406

Illuminated Check Engine warning lamp is the most obvious indicator
Engine may enter limp-home mode with noticeably reduced power output
Fuel economy often drops compared to normal driving patterns
EGR-related systems may operate erratically or cease functioning entirely
In some vehicles, exhaust smell or rough idle accompanies the fault
Performance degradation varies depending on which specific circuit is affected

What Causes P1406

Short circuit between the signal wire and a power source in the harness
Failed DPFE sensor internally shorting the signal line to voltage
Broken or corroded ground connection at the sensor mounting point
Damaged wiring insulation allowing power feed crossover
Loose, corroded, or physically damaged connector terminals
Control module output driver failure on that specific circuit
Blown fuse protecting the DPFE circuit power supply
Failed solenoid or actuator feeding into the same circuit

How to Diagnose P1406

Connect an OBD2 scanner and verify P1406 is active. Record the associated freeze frame data before clearing anything — this snapshot tells you exactly what conditions triggered the fault.
Pull all stored codes from the PCM. Related diagnostic trouble codes in the same circuit often point directly to the root cause. Check manufacturer TSB databases for known complaints on your specific make and model.
Perform a thorough visual inspection of the wiring harness and connectors serving the DPFE system. Look for damaged insulation, corrosion buildup, bent pins, or wires pulled free from their terminals.
With the DPFE sensor disconnected, probe the harness connector using a multimeter. If you still measure high voltage on the signal circuit, the problem lies in the wiring itself — likely a short to power somewhere upstream.
Measure reference voltage, signal return continuity, and ground resistance at the component connector. Compare readings against manufacturer specifications if available.
Conduct a wiggle test on the harness while monitoring live data on your scanner. Intermittent signal drops or spikes often reveal broken wires that only fail under vibration.
After repairs, clear the code and complete a full drive cycle matching the freeze frame conditions. Confirm the warning light stays off and P1406 does not reappear.

Repair Options and Cost Estimates

Correcting P1406 means addressing whichever component actually caused the circuit fault:

DPFE sensor or related actuator replacement runs $150–$500 for parts and labor
Wiring harness repair or connector replacement costs $80–$250 depending on extent
Control module diagnosis and repair typically ranges $300–$1,000 if the PCM itself is faulty

Total Repair Cost for P1406

Budget planning for P1406 varies significantly based on root cause. Most straightforward repairs fall in the $150–$500 range for a failed sensor. Wiring fixes usually stay under $250 unless extensive harness replacement becomes necessary. The $300–$1,000 scenario applies only when the Powertrain Control Module requires attention — an infrequent but expensive outcome. An accurate diagnosis before purchasing parts prevents wasted money on unnecessary replacements.

Can You Drive with P1406?

In most vehicles, P1406 permits continued operation with potential performance limitations. The EGR system may stop working, reducing fuel efficiency, but your car remains driveable. Treat this as a moderate-priority repair rather than an emergency, though you should schedule service promptly to prevent potential catalytic converter damage from prolonged operation with uncontrolled exhaust gas flow.