P0405: Exhaust Gas Recirculation Sensor A Circuit Low
Key takeaways
- P0405 means the signal from the EGR valve's position sensor dropped below the range the engine computer accepts.
- It's an electrical code first: wiring, the connector and the sensor built into the EGR valve cause most of them; carbon is a less common trigger.
- Most cars drive normally with P0405, but stalling at stops or knocking under load means the valve is also stuck and needs attention soon.
- Jeep and Ram have engine computer updates that address P0405, and Hyundai has a bulletin for 2024 EGR valves with a contaminated sensor.
- Most P0405 repairs at a US independent shop run $100–$700; a new EGR valve with its built-in sensor is $250–$700.
What P0405 means
The sensor that reports your EGR valve’s position is sending a signal that’s too low to be real.
Scanners call it “Exhaust Gas Recirculation Sensor ‘A’ Circuit Low.” The EGR valve feeds a little exhaust back into the intake to cut NOx. On most modern cars the valve has a position sensor built in, fed a 5-volt reference by the engine computer. The sensor returns a voltage that rises and falls with the valve’s position. P0405 sets when that voltage sits below the lowest value a working sensor can produce. On some older designs the “sensor A” is a separate pressure sensor with small hoses to the exhaust, and the same code applies to it.
Is it safe to drive?
Yes, on most cars, for now. The engine usually runs normally, and some computers simply cut back EGR use when they can’t trust the sensor.
What changes the answer is a valve that is also stuck. Stuck open, it causes a rough idle or stalling at stops. Stuck shut, you may hear pinging when you accelerate hard. With either, drive gently and get it fixed within days.
Causes, ranked
| Cause | How you confirm it | Typical cost (US independent shop, 2026) |
|---|---|---|
| Wiring or connector at the EGR valve | Check the 5-volt reference, ground and signal at the plug; look for heat damage, corrosion and chafed wires | $100–$250 |
| Failed position sensor inside the EGR valve | Reference and ground good at the plug, but the signal stays low as the valve is commanded | $250–$700 (valve with sensor) |
| Software calibration on specific models | A manufacturer bulletin matches your car and code | Often $0 under warranty; $100–$200 otherwise |
| Shorted 5-volt reference shared with another sensor | Other sensor codes set at the same time; reference voltage low with the EGR valve unplugged | $100–$250 |
| Carbon jamming the valve at one end of its travel | Valve won’t move on command; carbon on the pintle | $150–$500 (clean valve and passages) |
| Separate EGR pressure sensor or its hoses (some older cars) | Hoses cracked or clogged; sensor voltage doesn’t change with engine load | $100–$300 |
What to check first
- Read every stored code. Several sensor codes at once point to a shared 5-volt reference problem, not the EGR valve. P0405 with P0404 suggests the valve or its sensor.
- Check for a bulletin. The pattern is small but useful: Jeep has an ECM reprogram for P0405/P0406 on the 2011–2013 Grand Cherokee, Ram has a PCM update for the 2017 2500 with the 6.4L, and Chrysler has an engineering tip for the 6.4L cooled EGR assembly. Hyundai has a bulletin for 2024 Sonata and Tucson EGR valves whose sensor may have been contaminated during manufacturing.
- Inspect the connector and harness near the valve. Heat and water are the usual culprits.
- Measure the reference, ground and signal at the plug before buying a valve. This is a 15-minute test at a good shop.
- Replace the valve only once the wiring checks out.
- Clear it and drive after the repair to confirm it stays off.
What it costs
The cheap outcome is a connector or wiring repair, or a software update, $100–$250 or free under warranty. The common outcome on modern cars is a new EGR valve with its built-in sensor at $250–$700. Trucks, diesels and cooled-EGR systems run above that. A wiring test first keeps you from buying a valve you don’t need. If you want a second opinion, ask in the chat.
Related codes
P0406 is the same sensor reading too high. P0404 (valve position doesn’t match command) and P0401 (insufficient flow) often appear alongside it when the valve is also sticking, and P0403 is the valve’s control circuit.
What owners report to NHTSA
11 complaints filed with NHTSA mention P0405, 5 of them since 2015, across 8 different models. The component owners most often filed it under: fuel/propulsion system.
Most-reported models
| Vehicle | Complaints | Model years reported |
|---|---|---|
| CHEVROLET VOLT | 3 | 2016, 2017 |
Manufacturer service bulletins that name P0405
6 technical service bulletins and manufacturer communications filed with NHTSA mention P0405, from 4 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:
- HYUNDAI SONATA (2024), bulletin 11008136: The exhaust gas recirculation (EGR) valve assembly in certain vehicles may contain a sensor that was contaminated with solder flux during manufacturing, which could potentially result in an electrical short. An electrica…
- HYUNDAI TUCSON (2024), bulletin 11008137: The exhaust gas recirculation (EGR) valve assembly in certain vehicles (listed below) may contain a sensor that was contaminated with solder flux during manufacturing, which could potentially result in an electrical shor…
- RAM 2500 (2017), bulletin 10138930: Flash: 6.4L Powertrain Diagnostic and System Enhancements This bulletin involves reprogramming the Powertrain Control Module (PCM) with the latest available software. This bulletin fixes all vehicles listed and also cont…
- FCA ALL MODELS (2006, 2007, 2008, 2009), bulletin 10150486: Cooled EGR Assembly This Tech Tip applies to Ram DJ, D2, DD trucks for 2014 and 2015 model years equipped with the 6.4 ESA and 6.4 ESB HEMI Heavy Duty engines. Please contact engineering prior to replacing any components…
- JEEP GRAND CHEROKEE (2011, 2012, 2013), bulletin 10148595: Flash: DTC P0405 / P0406 - MIL Light On This bulletin involves reprogramming the Engine Control Module (ECM) with new software. A small number of customers may report the MIL light is on. On further inspection Diagnostic…
Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.
Frequently asked questions
Is P0405 a bad EGR valve?
Sometimes. On most modern cars the position sensor is built into the valve, so a failed sensor means a new valve. But a broken wire, a corroded pin or a shorted 5-volt reference gives the same low signal, so the wiring gets tested before the valve is replaced.
Can I drive with a P0405 code?
Usually, yes. Many cars run normally and some reduce EGR use as a precaution. If you get a rough idle, stalling at stops or knocking when you accelerate hard, the valve itself is probably stuck too; book it in soon.
Can cleaning the EGR valve fix P0405?
Occasionally, when carbon has jammed the valve at one end of its travel. More often P0405 is electrical, so cleaning alone won't clear it. Test the sensor signal and wiring first.
How much does it cost to fix P0405?
At a US independent shop, a wiring or connector repair runs $100–$250, a software update $100–$200 or free under warranty, and a new EGR valve $250–$700. Trucks and diesels cost more.