P0403: How to Diagnose & Fix — Exhaust Gas Recirculation Circuit Malfunction
64 vehicles · 20 makes · $20-$15,000 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.
Toyota Tundra · 2007–2021
The 5.7L iForce V8 engine is known for developing oil leaks at the cam tower due to Toyota's use of gray RTV silicone sealant instead of a proper gasket from the factory. The sealant degrades over time, particularly at the rear of the cam towers where the engine is slanted.
Common Symptoms
- Oil residue visible in wheel wells
- Burning oil smell
- Oil spots on driveway
- Low oil level between changes
- Shiny wetness around cam tower area
How to Fix
Repair requires removing the top of the engine, timing chain, and cam tower to reseal with proper RTV. This is labor-intensive and typically costs $2,500-$4,000 at a dealer. DIY is possible for experienced mechanics.
Owner tips & cautions
- TipDIY repairs can save significantly - dealer charges $2,500-$4,000 but DIY costs are typically 50-70% less
- TipGet a proper diagnosis before replacing parts - similar symptoms can have different causes
- TipSearch Toyota Tundra forums and owner groups for real-world experiences and DIY guides
- TipGet multiple quotes from independent mechanics - dealer prices can be 2-3x higher for the same repair
Nissan Leaf · 2011–2023
The Nissan Leaf uses an air-cooled lithium-ion battery that degrades faster than liquid-cooled competitors. Hot climates (Arizona, Texas) accelerate degradation significantly. Early models (2011-2015) with 24 kWh packs can lose 30-40% capacity within 5-7 years. Nissan provides an 8-year/100,000-mile battery warranty covering loss below 9 bars (approximately 66% capacity) on the dashboard gauge.
Common Symptoms
- Range decreasing over time
- Battery capacity bars disappearing on dashboard
- Reduced range in hot weather
- Battery temperature warning
- Rapid charging speed declining
How to Fix
Monitor battery health using LeafSpy app and OBD2 adapter. Keep battery between 20-80% charge for daily use. Avoid frequent DC fast charging. Park in shade in hot climates. If below 9 bars within warranty period, Nissan will replace battery modules. Aftermarket battery replacement/upgrade available from $5,000-8,000.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- LELink² configurable Bluetooth Low Energy OBD-II adapter KSO1702
Configure its auto-off behavior, do not leave an unverified adapter powered indefinitely, and do not use it to perform high-voltage repair or to promise warranty approval.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Toyota Prius · 2004–2015
Gen 2 (2004-2009) and Gen 3 (2010-2015) Prius NiMH battery packs commonly fail between 8-15 years. Individual cell degradation causes voltage imbalances, triggering warning lights and reduced performance. Battery cooling fan clogging accelerates failure.
Common Symptoms
- Red triangle warning light
- P0A80 code - Replace Hybrid Battery Pack
- Decreased fuel economy
- Reduced power and acceleration
- Battery SOC fluctuating rapidly
How to Fix
Replace hybrid battery pack or individual failed cells. Toyota OEM pack costs $2,200-$3,500. Refurbished options from Green Bean Battery ($1,500 with warranty) or Dorman (587-001 for Gen 2, 587-003 for Gen 3). DIY cell replacement possible with individual cells ($20-40 each). Clean battery cooling fan first - located behind rear seat on driver side.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Greentec Auto 2004-2009 Prius hybrid battery with new cells
replace a professionally diagnosed failed Gen-2 traction-battery pack as a complete matched assembly Fitment/availability: 2004-2009 Prius Gen 2 NiMH pack, 200 V and 28 modules; confirm VIN, service area, core deposit/return and warranty…
- Greentec Auto 2010-2015 Prius hybrid battery with new cells
replace a professionally diagnosed failed Gen-3 liftback traction-battery pack as a complete matched assembly Fitment/availability: 2010-2015 Prius Gen 3 liftback NiMH pack, 6.5 Ah and 28 modules; not a Prius v or Plug-in pack, and core/…
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Sources for this issue (1)
Volkswagen Golf · 2008–2020
Ford F-250 Super Duty · 2011–2019
Find P0403 by make
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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 $20 to $15,000, depending on the vehicle and root cause.
Which vehicles are affected by P0403?
Au7o has documented P0403 across 64 vehicle models from 20 manufacturers: BMW, Chrysler, Citroen, Dodge, Ford, GMC, Honda, Hyundai, Jeep, Kia, Land Rover, Mazda, Nissan, Peugeot, Porsche, RAM, Subaru, Toyota, Volkswagen, Volvo.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.