P0403: How to Diagnose & Fix — Exhaust Gas Recirculation Circuit Malfunction
9 vehicles · 7 makes · $60-$3,500 repair
How to diagnose and fix P0403: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Ford F-250 Super Duty · 2011–2019
The EGR (Exhaust Gas Recirculation) cooler on 2011-2019 6.7L Power Stroke diesel engines is prone to clogging with soot and eventually failing, particularly on trucks used for highway driving, light loads, or trucks that idle extensively. The EGR cooler recirculates cooled exhaust gas back into the intake to reduce NOx emissions. Over time, soot accumulates in the cooler's internal passages and restricts exhaust gas flow through the cooler core, and a cooler that overheats can fail. When it fails, exhaust gases enter the coolant system, causing overheating and "puking" coolant from the degas bottle. The 2011-2014 models are particularly susceptible due to narrow internal coolant passages. Ford TSB 13-6-5 (superseding 12-6-14) covers 2011-2012 6.7L trucks with DTC P0401 and P2457, calling for EGR cooler core replacement under normal New Vehicle Limited Warranty coverage. The EGR cooler for 2011-2016 is OEM part BC3Z-9V425-A; 2017+ is HC3Z-9V425.
Common Symptoms
- Coolant loss with no visible external leak
- Coolant reservoir overflows or "pukes" coolant
- White smoke from exhaust (coolant in combustion)
- Engine overheating warning
- DTC codes P0401 (Insufficient EGR Flow) or P2457 (EGR Cooler Performance)
- Bubbling or foaming in coolant degas bottle
- Loss of power under load (especially towing)
- White deposits around degas bottle cap
How to Fix
Replace EGR cooler (BC3Z-9V425-A for 2011-2016; HC3Z-9V425 for 2017+). For 2011-2012 trucks with DTC P0401 (Insufficient EGR Flow) and P2457 (EGR Cooler Performance), Ford TSB 13-6-5 applies; coverage follows the truck's normal warranty, so have a Ford dealer check the VIN. Preventive: use a fuel additive (Diesel Kleen, Hot Shots Secret EDT) to reduce soot. Perform regular EGR cleaning at 60,000-mile intervals. Upgrade kits from Sinister Diesel and Dorman (904-405 kit) include both EGR cooler and gaskets.
Sources for this issue (2)
Chrysler Crossfire · 2004–2008
The Crossfire (built on Mercedes SLK R170 platform, sharing 80% of components) commonly experiences EGR solenoid failures and premature catalytic converter failure. The EGR solenoid is the most common cause of check engine lights. Catalytic converter rattles and fails, especially noticeable when accelerating from cold.
Common Symptoms
- Check engine light (EGR codes)
- Rattling noise from underneath when accelerating from cold
- Failed emissions inspection
- Rough idle
- Reduced fuel economy
How to Fix
Confirm the EGR fault from the stored codes, then replace the failed EGR solenoid/valve (use the Mercedes M112 part, commonly listed as A1121400060, or the Mopar Crossfire part; confirm by VIN). Replace catalytic converter if rattling. Many Mercedes SLK R170 parts are direct replacements at lower cost. Use Mercedes dealer or independent Mercedes shop for best results.
Sources for this issue (4)
Peugeot 308 · 2007–2021
On diesel 308s (1.6 HDi and 2.0 BlueHDi), the exhaust gas recirculation (EGR) valve sends some exhaust back into the intake. Over time, soot and carbon build up in the valve and its passages until it moves only partly or sticks. Short town trips make this worse because the engine rarely gets fully hot, and a dirty air filter, poor-quality oil and skipped servicing speed it up too. Owners report rough or unstable idle, stalling at idle, slow revving or hesitation when accelerating, and power loss, mostly between about 1,500 and 3,000 rpm. Some also see smoke or higher fuel use. The engine warning light may come on, sometimes with limp mode, but it does not always. One 1.6 HDi owner with rough idle and stalling had EGR-related codes stored, including P0409, P1462, P0490 and P1459, and forum members pointed to a carbon-coked EGR valve. On a 2016 308 GT Line 2.0, the owner felt sluggish and hesitant with no fault codes stored. Blocking off the EGR as a test made the car livelier, which pointed to the EGR circuit even without a code.
Common Symptoms
- Rough or unstable idle, sometimes stalling at idle
- Hesitation and loss of power, mostly between about 1,500 and 3,000 rpm
- Slow rev rise when accelerating
- Engine warning light, sometimes with limp mode (not always lit)
- Smoke from the exhaust
- Higher fuel consumption
How to Fix
1. Read the fault codes with a scan tool that can talk to the Peugeot engine ECU (Diagbox or an equivalent). Look for EGR-related codes, but don't rule out the valve if none are stored. Some owners have had EGR symptoms with no codes. 2. Run an EGR actuator test before buying parts. A valve can look clean and still not move. Forum members also suggest checking the valve's wiring and connector, since the descriptions for these codes list the harness and connectors as possible causes. You should normally hear a short ticking from the valve at shutdown when it runs its self-clean cycle. 3. If the valve is only lightly or moderately carboned, remove it and clean it with EGR cleaner and a brush, then clear the codes. A fuel additive only helps prevent buildup or deal with light deposits. 4. Replace the valve if symptoms come back after two cleanings, if it is stuck and won't move after cleaning, if the body is cracked or if it leaks. On high-mileage cars (over about 150,000 km), replacing it can work out cheaper than cleaning it again and again. 5. Don't blank off the EGR permanently. One owner who did it as a test found the car ran better but used more fuel, and a forum moderator warned the ECU may react badly to it. We found no recall or warranty extension for this. ClickMechanic gives an average of about £363 to replace the valve on a 308 in the UK.
What you need to diagnose it
The repair instructions explicitly call for reading stored codes. Use a scanner that can read the named code families before choosing a repair.The recommended scanner supports these code families; confirm your exact year, model and module coverage before buying.
ANCEL AD310 Classic OBD-II Scanner
Read & clear engine (P) codes
$20–$40View
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Reading and clearing the code is DIY work. Module replacement or reprogramming is not — most modules are VIN-programmed, so a new one does nothing until a shop codes it to your car. Check for an open recall or service bulletin before buying anything.
Sources for this issue (5)
Porsche Macan · 2014–2018
Volkswagen Jetta · 2009–2014
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P0403 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0403 mean?
P0403 stands for "Exhaust Gas Recirculation Circuit Malfunction." This emissions code indicates a malfunction in the exhaust gas recirculation (EGR) control circuit. The EGR system routes a small amount of exhaust back into the intake to lower combustion temperatures and reduce nitrogen-oxide emissions, and the computer commands the EGR valve open and closed through this circuit. The code sets when the electrical control signal to the EGR valve or its solenoid is out of the expected range — for example, an open, short, or a commanded change that doesn't produce the right feedback. It generally points to an electrical or wiring problem in the EGR control circuit, or the EGR valve/solenoid itself, rather than carbon clogging alone.
What are the most common causes of P0403?
The most common causes of P0403 are: Faulty EGR valve or EGR solenoid, Damaged wiring or connector in the EGR control circuit, Open or short in the EGR control wiring, Corroded or loose EGR connector, Blown fuse or lost power supply to the EGR circuit, Carbon buildup binding the EGR valve, Faulty engine control module or driver circuit. The specific cause varies by vehicle.
How much does it cost to fix P0403?
Repair costs for P0403 range from $60 to $3,500, depending on the vehicle and root cause.
Which vehicles are affected by P0403?
Au7o has documented P0403 across 9 vehicle models from 7 manufacturers: Chrysler, Ford, Land Rover, Mazda, Peugeot, Porsche, Volkswagen.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.