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Error Code P1401 is defined as DPFE (Differential Pressure Feedback Sensor) Error.
This error code is a manufacturer-specific trouble code, meaning it does not apply to all vehicles makes. Rather, it applies only to specific vehicle makes, such as Ford and Hyundai. Specification on the definition, troubleshooting, and repairs still vary from one make and model to another.
The job of the EGR system or Exhaust Gas Recirculation system is to minimize Nitrogen Oxide (NOx) emission. This is done by redirecting a small amount of exhaust gas back to the upper intake to get mixed with the air/fuel charge. The result is a diluted air/fuel mixture, which means less oxygen per cubic foot. It burns cooler, and the combustion chamber temperature is both reduced, which results in a lower emission of NOx.
For vehicles like Ford, the DPFE/EGE system is controlled by the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes). The system employs the EGR valve, an EVR (electronic vacuum regulator) and a Delta Pressure Feedback EGR Sensor (DPFE).
The DPFE sensor measures the flow of EGR across an orifice which is found inside the special EGR tube. This hole is located between two hose ports coming off the tube, which is also connected to the DPFE sensor with special heat-resistant hoses. If the EGR valve is open, a pressure differential is created across the orifice (intake manifold pressure vs. exhaust pressure). By design, the pressure difference is measured by the DPFE sensor in terms of voltage. The DPFE voltage signal output to the PCM directly proportional to the flow of the exhaust gas that enters the intake manifold.
As said earlier, the EGR valve has a feedback sensor called the DPFE sensor. When this sensor goes bad or fails, the Error Code P1401 is triggered, along with other related trouble codes, which are usually P0140 variants. The most common symptom is rough idling, which is caused by improper exhaust gas regulation (either too much or too little exhaust is being recirculated back to the cylinders), which interrupts proper combustion.
As with other error codes, this code activates the Check Engine light and registers the trouble code to the vehicle’s system. Other symptoms include:
- Rough idle
There are many possible causes for this error code. Some of the most common causes are:
- Defective DPFE sensor
- Open or shorted DPFE sensor harness
- Poor electrical connection in DPFE sensor circuit
- Damaged PCM (rare)
How to Check
To diagnose for this error code, you should start by checking the DPFE sensor.
Repair or replace DPFE sensor harness
Repair or replace electrical connection in the DPFE sensor circuit
How to Fix
DPFE sensor replacement
Check, clean, and replace the EGR valve along with its input tube.
PCM is a rare cause of this error code, but if everything seems to be okay and you still experience the problem of the error code, then that means your PCM has gone bad. It should be updated before repair, or completely replace the whole thing instead.