P0402🌫 Emissions / EGRStop and fix promptly

P0402: EGR Flow Excessive Detected (Meaning, Causes, Fixes)

Reviewed 2026-10-23 · Based on 2 cited source(s)

What P0402 means

The EGR system feeds a small amount of exhaust back into the intake to lower combustion temperature and cut oxides of nitrogen (NOx). RepairPal says it is usually no more than 10 percent of the intake air. OBD-Codes.com describes three main parts: the EGR valve, an actuator solenoid and a differential pressure (DPFE) sensor, which together deliver the right amount of recirculation for engine temperature and load. P0402 means the system detected excessive EGR flow. RepairPal explains that the computer runs EGR monitoring tests, usually during steady freeway and steady city driving, and watches intake manifold pressure, the front oxygen sensor signal, EGR valve position, knock and the DPFE reading. P0402 is often set when those readings change too much, or when the sensors still show EGR flow after the tests are complete. It is a generic code that applies to OBD-II vehicles, though repair steps vary by make and model. The sources differ in a few ways. OBD-Codes.com names a faulty DPFE sensor as the most likely cause, while RepairPal lists the DPFE as one of several feedback sensors alongside the MAP sensor and EGR valve position sensor, and puts more weight on the valve being held open by too much vacuum or electrical signal, a bad vacuum solenoid, or a valve that opens too far or won't close. OBD-Codes.com's cause list also includes carbon blockage and an EGR valve that isn't opening for lack of vacuum, which are usually linked to too little flow (P0401) rather than too much; RepairPal does not list them for P0402. RepairPal rates the code Urgent; OBD-Codes.com gives no rating.

Severity: can I keep driving?

Stop and fix promptly

Get it checked soon. RepairPal rates P0402 Urgent, meaning immediate action is needed, though it also says most drivers notice nothing; in some cases the engine can die at stop signs, idle roughly, hesitate, misfire or lose power, especially when accelerating. OBD-Codes.com gives no severity rating and says the engine may surge off idle. If the engine stalls at stops or runs badly, avoid driving in traffic until it's fixed.

Common symptoms

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

  1. Faulty DPFE (differential pressure feedback) sensor (OBD-Codes.com, most likely; RepairPal lists it among feedback sensors)
  2. Too much vacuum or electrical signal to the EGR valve (RepairPal only)
  3. EGR valve defective, opening too far or not closing properly (RepairPal); faulty EGR valve (OBD-Codes.com)
  4. Malfunctioning EGR vacuum supply solenoid (RepairPal only)
  5. Faulty feedback from the MAP sensor or EGR valve position (EVP) sensor (RepairPal only)
  6. Carbon blockage in the EGR, or the valve not opening for lack of vacuum (OBD-Codes.com only)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

  1. Don't start by replacing the EGR valve. OBD-Codes.com says people often replace it only to have the code return, and RepairPal says P0402 is often not the valve itself.
  2. OBD-Codes.com suggests checking the voltage at the DPFE sensor at idle and with the EGR open. RepairPal says the DPFE reading should rise from about 0.5 volt to at least 1 to 3 volts as the valve opens, watched on a data-streaming scan tool.
  3. Check whether the EGR valve is getting vacuum when it shouldn't, such as at idle (RepairPal). Some systems use two vacuum solenoids to supply and bleed vacuum, and if either fails the valve can be open when it shouldn't be.
  4. RepairPal suggests raising the engine to about 2000 RPM, opening the EGR valve fully (with a vacuum pump, or a bi-directional scan tool on an electronic valve) and letting it snap closed. If the idle gets smoother, the valve may not be closing properly.
  5. With a scan tool, the EGR valve position reading should drop to 0 percent at idle (RepairPal). If it doesn't, a piece of carbon may be stuck between the valve tip and its seat.
  6. RepairPal also suggests disconnecting the EGR valve and test driving to see whether performance changes, and recording the freeze frame data so you can repeat the conditions when the code set.

Typical fixes

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

  • The engine stalls at stops or idles very roughly
  • You don't have a data-streaming scan tool to watch the DPFE and EGR position readings
  • The code comes back after a new EGR valve or DPFE sensor
  • Your vehicle uses an electronic EGR valve that needs a bi-directional scan tool to test
  • You need to pass an emissions inspection soon

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Can I drive with P0402?

Gently and for a short time, if the engine runs normally. RepairPal rates it Urgent, though it says most drivers notice nothing, and it can cause stalling at stop signs, rough idle or hesitation in some cases. Get it diagnosed soon, especially if the engine stalls.

Is P0402 a bad EGR valve?

Not usually, according to both sources. OBD-Codes.com says the most likely fix is the DPFE sensor and that replacing the EGR valve often doesn't solve it, and RepairPal says the code is often caused by the controls or feedback sensors rather than the valve itself.

What's the difference between P0401 and P0402?

P0401 means the computer saw too little EGR flow, and P0402 means it saw too much, or flow when there should be none, like at idle.

How much does it cost to fix P0402?

Neither source gives a repair cost for P0402. It can be a sensor, a vacuum solenoid, a hose or the valve, so diagnose it before buying parts.

Sources

  1. OBD-Codes.com: P0402 Exhaust Gas Recirculation (EGR) Flow Excessive Detected
  2. RepairPal: P0402 Exhaust Gas Recirculation "A" Flow Excessive Detected (rated Urgent)

Last reviewed 2026-10-23. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.