P0405: How to Diagnose & Fix — Exhaust Gas Recirculation Sensor 'A' Circuit Low
5 vehicles · 5 makes · $50-$2,800 repair
How to diagnose and fix P0405: 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.
GMC Sierra 3500HD · 2008–2016
The exhaust gas recirculation cooler on 6.6L Duramax LMM and LML engines is prone to internal cracking, allowing coolant to enter the EGR system and combustion chamber. Owners experience white steam from the exhaust, unexplained coolant loss, and in severe cases hydrolocking. This is a well-documented failure mode covered under extended warranty campaigns and referenced in NHTSA complaint database for 2008–2016 model years.
Common Symptoms
- White or grey smoke from exhaust at idle or under load
- Unexplained coolant loss without visible external leak
- Coolant smell from exhaust or air intake
- Engine overheating or coolant temperature fluctuations
- Milky residue in coolant reservoir or degas bottle
How to Fix
Replace EGR cooler assembly (GM part 98010538 for LML, or ACDelco 12642878 for LMM) and thoroughly flush cooling system. Inspect EGR valve for carbon buildup and replace if necessary. Upgraded aftermarket EGR coolers (Fleece Performance, BorgWarner) offer improved durability. Labor is 4–8 hours; coolant flush and fill required.
Sources for this issue (1)
Chrysler PT Cruiser · 2001–2010
The EGR (Exhaust Gas Recirculation) valve on the 2.4L engine clogs with carbon deposits and sticks open or closed. When stuck open, it causes rough idle, stalling, and hesitation. When stuck closed, it increases NOx emissions and may trigger a check engine light. The EGR passages in the intake manifold also clog with carbon, reducing effectiveness even with a functioning valve. The turbo model is especially prone due to higher exhaust temperatures.
Common Symptoms
- Rough idle or stalling at idle
- Check engine light with EGR flow codes
- Hesitation during acceleration
- Failed emissions test for high NOx
- Engine surging or hunting at idle
How to Fix
Remove the EGR valve and clean it with carburetor cleaner and a wire brush. Clean the EGR passages in the intake manifold with a long bristle brush. If the valve diaphragm is torn or the pintle is worn, replace the EGR valve (Standard Motor Products EGV880 or equivalent). Also clean the EGR tube connecting the exhaust manifold to the valve. Budget $150-$400 for cleaning and/or replacement.
Sources for this issue (1)
Hyundai Venue · 2024–2024
A sensor inside the EGR valve may have been contaminated with solder flux during supplier manufacturing and can short. Because the EGR valve and crank position sensor share a power circuit, the short can turn on the check-engine light or cause a sudden loss of motive power, which increases the risk of a crash. Applies to: Certain 2024 Hyundai Venue vehicles with the Gamma 1.6L MPI engine built January 12 – March 4, 2024 (2,364 Venues; the recall also covers some 2024 Elantra and Kona). Hyundai campaign 260. Only a Hyundai dealer can confirm whether a specific VIN is included and whether the repair has been done.
How to Fix
Have a Hyundai dealer check the VIN for recall 24V308 (campaign 260). The remedy is replacement of the EGR valve assembly and its gasket at no cost to the owner; Hyundai also offers reimbursement for eligible out-of-pocket repairs of this condition under its plan filed with NHTSA. This is engine-bay electrical and emissions work; no DIY repair or retail part is recommended.
Sources for this issue (2)
Ford F-150 · 1997–2004
Opel Astra · 2009–2015
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P0405 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 P0405 mean?
P0405 stands for "Exhaust Gas Recirculation Sensor 'A' Circuit Low." P0405 is a generic OBD-II code meaning the engine computer detected an abnormally low voltage signal from the Exhaust Gas Recirculation (EGR) sensor 'A' circuit. This sensor reports the EGR valve's position or flow, which the computer uses to control exhaust gas recirculation for lowering emissions and combustion temperatures. A low signal indicates the reading is below the expected range, often due to a wiring or sensor fault. It mainly affects emissions and may cause light drivability issues but is not an immediate safety concern.
What are the most common causes of P0405?
The most common causes of P0405 are: Faulty EGR position sensor (or DPFE sensor), Open, shorted, or corroded EGR sensor wiring/connector, EGR valve stuck or carbon-clogged, Loss of reference voltage or ground to the sensor, Poor connector contact / pin corrosion, Damaged EGR valve assembly, PCM fault (rare). The specific cause varies by vehicle.
How much does it cost to fix P0405?
Repair costs for P0405 range from $50 to $2,800, depending on the vehicle and root cause.
Which vehicles are affected by P0405?
Au7o has documented P0405 across 5 vehicle models from 5 manufacturers: Chrysler, Ford, GMC, Hyundai, Opel.
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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.