P0402: EGR Flow Excessive Detected

What this code means

P0402 may mean the PCM is seeing more EGR flow than expected, or it may be receiving a sensor signal that makes EGR flow appear excessive.

What the vehicle may do

The vehicle may have a rough idle.
The code can set with little noticeable driveability change.
The concern may occur during idle or under captured driving conditions.

Possible fault areas

Possible DPFE sensor, hose, or orifice tube concerns.
Possible EGR valve, EGR cooler, or EGR control circuit concerns.
Possible connector, wiring, MAP, MAF, cooling-related, or controller-side concerns.

Diagnostic path

Open and basic direction

On this 2015 through 2025 F-150 with the 2.7 EcoBoost, P0402 means the PCM may be seeing more EGR flow than it expects. In plain terms, the truck may have unwanted EGR flow, or it may only look that way because of a DPFE sensor, hose, wiring, or EGR control issue. The driver may notice a rough idle, but the code can also set under captured driving conditions, so reproduce the operating conditions instead of guessing. Broadly, keep the DPFE sensor and its hoses, the orifice tube, the EGR valve and cooler area, EGR and DPFE circuits, MAP or MAF input concerns, cooling-related concerns, and controller-side possibilities in mind. Start with the basic system checks. If other codes are present, check what they mean first, and repair circuit faults before chasing range or performance faults. For P0402 on this engine, the directed diagnostic path starts on the DPFE side of the EGR system. The key logic is that the monitor compares the stored key-on engine-off DPFE signal to the idle signal; a DPFEGR PID reading that is greater at idle than during KOEO by 0.5 volt, or a rough engine idle, may indicate a concern.

Check DPFE reference, return, and signal circuits

With the ignition off, disconnect the Differential Pressure Feedback EGR sensor connector. Turn the ignition on and check the reference and signal return between C1068 Pin 3 and C1068 Pin 2. You want 4.5 V - 5.5 V. If that is not there, leave this path and diagnose the reference circuit problem. If it is in range, turn the ignition off, disconnect the PCM connector, and check the DPFE signal circuit between C1068 Pin 1 and C1232E Pin 79. Resistance needs to be less than 5 Ω. If it is not, repair the open, clear the PCM codes, and repeat the self-test. Next, check that DPFE signal circuit for a short to ground. The resistance at C1068 Pin 1 needs to be greater than 10000 Ω. If it is not, repair the short, clear the codes, and repeat the self-test. Then turn the ignition on and check the same DPFE signal circuit for a short to voltage. If any voltage is present, repair the short, clear the codes, and repeat the self-test. If no voltage is present, continue on.

Wiggle test and DPFE hose inspection

Now reconnect the DPFE sensor and the PCM connector. Turn the ignition on, access the PCM, and monitor DPFE_PRES in kPa and DPFE_V in V. Work from the sensor back toward the PCM and wiggle, shake, and bend small sections of the harness. If either reading changes, or the concern shows up while you are moving the harness, repair what you find, clear the codes, and repeat the self-test. If the harness passes, inspect the DPFE pressure hose routing. Look at the upstream and downstream hoses for leaks, restrictions, water intrusion, and carbon build up. Also inspect the DPFE sensor and orifice tube assembly for restriction or damage at the pick up tubes, water intrusion, and carbon build up. If water intrusion is present, install a new Differential Pressure Feedback EGR sensor, clean the hoses and orifice tube, clear the PCM codes, and repeat the self-test. For any other concern found here, repair as necessary, clear the codes, and repeat the self-test. If nothing is found, move to the DPFE output check.

DPFE output check with vacuum

Before testing the DPFE sensor response, make sure a previous repair has not swapped the DPFE hoses onto the opposite ports. Connect the pressure hoses to the DPFE sensor, turn the ignition on, monitor DPFE_PRES and DPFE_V, and record the DPFE value. Start the engine and record it again. The difference between engine off and engine running must be less than 0.075 volts (0 kPa). Then turn the ignition on, disconnect the pressure hose at the DPFE sensor port closest to the electrical connector, and connect a hand vacuum pump to that same port. With ignition on and no vacuum applied, the DPFE PID value must be between 1.8 and 2.2 volts (0 kPa). Apply 27 - 30 kPa (8 - 9 in-Hg) vacuum and hold it for 10 seconds. The DPFE PID value must increase to greater than 4 volts (14.7 kPa). When the vacuum is released, it must drop back to between 1.8 and 2.2 volts (0 kPa) in less than 5 seconds. If the DPFE response indicates a sensor concern, install a new Differential Pressure Feedback EGR sensor, clear the PCM codes, and repeat the self-test. If the DPFE sensor response checks good and P0402 is still the code being diagnosed, continue into the EGR valve control side.

Check the EEGR connector and EGR control circuits

Turn the ignition on and check the code status again. For this P0402 path, the next move is the EEGR connector and EGR circuit checks. If the code is intermittent, wiggle the harness and connectors while taking measurements. Check the EEGR connector first. If the contacts are not clean and correctly seated, repair as necessary, clear the PCM codes, and repeat the self-test. If the connector is clean and seated, turn the ignition off, disconnect the EEGR assembly connector, and disconnect the PCM connector. Check the EGR circuits for opens between C1682 Pin 4 and C1232E Pin 2, and between C1682 Pin 5 and C1232E Pin 23. Each resistance check needs to be less than 5 Ω. If not, repair the open circuit, clear the codes, and repeat the self-test. Next, check the EGR circuits for shorts to ground at C1682 Pin 4 and C1682 Pin 5. The resistance needs to be greater than 10000 Ω. Then check for a short between the EGR circuits by measuring between C1682 Pin 4 and C1682 Pin 5. That resistance also needs to be greater than 10000 Ω. After that, turn the ignition on and check C1682 Pin 4 and C1682 Pin 5 for a short to voltage. If any voltage is present, repair the short, clear the codes, and repeat the self-test. If no voltage is present, continue to the EGR coil check.

Check EGR coil resistance and confirm operation

With the ignition off, check the EGR coils at the component side of the EEGR connector, between C1682 Pin 4 and C1682 Pin 5. Resistance must be between 1 - 900 ohms. If it is not in that range, install a new Electric Exhaust Gas Recirculation assembly, clear the PCM codes, and repeat the self-test. If the coil resistance is in range, reconnect the EEGR assembly connector and the PCM connector, then verify whether the concern is still present. If it is still present, install a new Electric Exhaust Gas Recirculation assembly, clear the PCM codes, and repeat the self-test. If the concern is no longer present, the system is operating correctly at this time, and the issue may have been caused by a loose or corroded connector.

Repair verification and takeaway

Keep verification separate from the testing. After any repair, clear the PCM codes, repeat the self-test, and confirm P0402 stays gone under the operating conditions that originally set the fault. The takeaway is simple: prove the DPFE signal and hoses first, then prove the EGR control circuits and EEGR assembly before condemning parts. For more diagnostic training, visit stepdiagnostics.com.