Code
P1401
LINCOLN
P — Powertrain
Differential Pressure Feedback Electronic Sensor Circuit High Voltage
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EN: 72
RU: 41
AI status
Completed
Completed
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Causes
- Damaged or pinched DPFE sensor wiring harness
- Short to battery voltage on the DPFE signal or reference circuit
- Corroded/loose connector at the DPFE sensor
- Failed DPFE (differential pressure) sensor
- Blocked, collapsed, or disconnected vacuum/pressure hoses to the sensor
- Restricted EGR passages or clogged exhaust ports causing abnormal pressure readings
Symptoms
- MIL/Check Engine Light illuminated (P1401 stored)
- Poor idle or rough running under some conditions
- Reduced engine performance or hesitation
- Failed emissions test (excess NOx, EGR-related emissions)
- Possible drivability issues when EGR operates
What to check
- Read and record freeze-frame and live data for DPFE voltage/differential pressure with a scan tool
- Verify whether the code is active or historical and erase then drive to confirm repeat occurrence
- Visual inspection of DPFE sensor, connector and hoses for damage, contamination or disconnection
- Backprobe the DPFE connector and check for proper reference voltage (typically from PCM), signal voltage and ground with a DVOM
- Perform continuity and resistance checks between sensor pins and PCM to look for opens/shorts
- Inspect EGR valve and related vacuum plumbing for restrictions, carbon buildup or collapsed hoses
Signal parameters
- Sensor supply/reference: typically a regulated reference (often ~5.0 V) from the PCM — verify against vehicle wiring diagram
- Sensor ground: good chassis/PCM ground with low resistance
- Signal voltage at zero differential: commonly near mid-rail (~2.0–2.5 V) depending on design
- High-voltage fault threshold: signal rising above about 4.5–4.8 V is considered high (confirm exact threshold with manufacturer data)
- Operating range: 0–5 V (most DPFE devices) — compare live data to expected values in repair manual
Diagnostic algorithm
- Retrieve freeze-frame and live data; note DPFE voltage and engine conditions when the code set.
- Visually inspect sensor, connector, and hoses for damage, contamination, collapsed tubing, or kinks. Repair or replace damaged hoses/connectors.
- With key on engine off, backprobe sensor connector: verify reference (5V) and ground presence. If reference is missing, trace to PCM and check wiring.
- With connector connected, monitor DPFE signal voltage at key on and during engine running. If signal is stuck high (>4.5 V), suspect short to battery/5 V or failed sensor.
- Perform pin-to-pin continuity and short-to-power/short-to-ground tests between the DPFE wiring and PCM. Repair any wiring faults.
- Disconnect sensor and measure resistance (if specified by manufacturer) or substitute known-good DPFE sensor to confirm sensor operation.
- Inspect and clean EGR passages and the pressure source lines to the sensor if carbon buildup or blockages are found; clear restrictions and re-test.
- If wiring and sensor check good, consider PCM as last resort — confirm with manufacturer diagnostic procedures before replacing PCM.
- After repair, clear codes and perform a road test and re-scan to confirm the code does not return.
Likely causes
- Open or shorted signal wire to battery positive
- Faulty DPFE sensor output stage stuck high
- Corroded connector causing intermittent high resistance and voltage float
- Collapsed/blocked DPFE/vacuum line causing abnormal pressure differential reading
Fault status
Status
PCM has detected an excessively high voltage on the Differential Pressure Feedback Electronic (DPFE) sensor circuit. This indicates the DPFE signal is above the expected operating range and may cause EGR/emissions control issues. Inspect sensor, wiring, connectors, and associated pressure/vacuum lines.
Repair difficulty: Medium
Diagnostic time: 1.0 to 2.5 hours
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