P0405
Fix within 1-2 weeksThe engine computer detects a low voltage signal from the Exhaust Gas Recirculation (EGR) sensor, indicating a problem with the EGR system's feedback.
Code P0405 means your engine computer detects a low voltage from the EGR sensor. Common causes: Faulty EGR valve (75%), wiring issues (20%), clogged passages (5%). Drivability: Yes, for short trips. Repair cost: $50-$250 DIY, $150-$500 professional.
Can I Drive With P0405?
Yes, for short trips only
Essential trips under 10 miles, avoid highways and heavy acceleration.
Stop driving immediately if: Flashing CEL, significant power loss, loud engine knocking, or stalling.
Symptoms of P0405
- 1Check Engine Light
- 2Rough idle or stalling
- 3Reduced engine power or acceleration
- 4Engine pinging or knocking (detonation)
- 5Failed emissions test
Common Causes of P0405
Parts most likely causing this code, ranked by probability
The sensor within the EGR valve itself is faulty, sending an incorrect low voltage signal to the PCM.
75% of P0405 cases are fixed by replacing the EGR valve
Damaged, corroded, or loose wiring or connector to the EGR valve or sensor causes an intermittent or constant low voltage signal.
20% of P0405 cases are fixed by repairing wiring or connectors
Carbon buildup restricts exhaust flow, preventing the EGR valve from operating correctly, which can affect sensor readings.
5% of P0405 cases are fixed by cleaning clogged EGR passages
Check These First (Before Buying Parts)
- Inspect the EGR valve's electrical connector for corrosion, bent pins, or loose connections.
- Check all vacuum lines connected to the EGR valve for cracks, breaks, or disconnections.
- Listen for any obvious vacuum leaks around the engine.
How to Diagnose P0405
- 1Visually inspect the EGR valve and its electrical connector for damage, corrosion, or loose connections.
- 2Check for any obvious vacuum leaks around the EGR valve or its associated hoses.
- 3Using a multimeter, test the voltage at the EGR sensor connector with the key on, engine off, to verify reference voltage and signal return.
- 4If possible, use a scan tool to monitor the EGR sensor's live data while operating the EGR valve (if applicable) to see if the voltage changes.
- 5Remove the EGR valve and inspect it for excessive carbon buildup that could be preventing proper operation.
P0405 on Popular Vehicles
Honda Accord
2003-2007Known for EGR valve failures due to carbon buildup or sensor issues, leading to P0405.
75% fixed by replacing the EGR valve
Toyota Camry
2002-2006EGR valve issues are common, often related to the sensor reporting low voltage.
75% fixed by replacing the EGR valve
Ford F-150
2004-2024EGR valve failures, sometimes due to carbon or electrical issues with the sensor, can trigger P0405.
75% fixed by replacing the EGR valve
Frequently Asked Questions
What does P0405 mean?
P0405 indicates the Powertrain Control Module (PCM) has detected a voltage signal from the Exhaust Gas Recirculation (EGR) sensor that is lower than expected. This means the PCM is not receiving the correct feedback about the EGR valve's position.
Can I drive with P0405?
Yes, you can drive with P0405 for short, essential trips. However, you should fix it within 1-2 weeks. Ignoring it can lead to reduced fuel economy, engine pinging, and increased emissions, potentially causing long-term engine damage.
Will P0405 clear itself?
No, P0405 will not clear itself. The underlying issue, usually a faulty EGR valve or wiring problem, must be repaired. The Check Engine Light will remain on until the fault is resolved and the system passes its self-test.
How do I fix P0405 myself?
Start by inspecting the EGR valve's electrical connector and vacuum lines for damage. If they look good, use a multimeter to test the EGR sensor's voltage. The most common fix is replacing the EGR valve itself, which often includes the sensor.
How much does it cost to fix P0405?
A DIY repair for P0405 typically costs $50-$250 for a new EGR valve and gasket. Professional repair at a shop costs $150-$500, covering parts and labor.
P0405 keeps coming back - why?
P0405 often returns if the root cause wasn't fully addressed. This can happen if you only cleaned the EGR valve instead of replacing a faulty sensor, if there's a persistent wiring issue, or if the EGR passages are still clogged after replacement.
Will P0405 fail emissions/smog test?
Yes, P0405 will cause your vehicle to fail an emissions or smog test. The Check Engine Light being on automatically results in a failure, and the EGR system is a critical component for emissions control.
What's the difference between P0405 and P0404?
P0405 specifically indicates a low voltage signal from the EGR sensor circuit. P0404 means the EGR valve's position sensor is reporting a value that is out of the expected range or performance, suggesting it's not opening or closing correctly, but not necessarily a low circuit voltage.
P0405 on Honda Accord?
P0405 is a common code on Honda Accords, particularly models from 2003-2007. It's frequently caused by a faulty EGR valve or carbon buildup in the EGR passages, which affects the integrated sensor's reading. Replacing the EGR valve and cleaning the passages usually resolves the issue.
Questions to Ask Your Mechanic
Did you check the EGR sensor voltage directly with a multimeter to confirm the low signal?
Good answer: Yes, I measured the voltage at the sensor connector and it was below the specified range, confirming a circuit low condition.
What did you find when you inspected the EGR valve and its passages for carbon buildup?
Good answer: I found significant carbon buildup preventing the valve from operating freely, and the sensor was also faulty, or the passages were clear, but the sensor itself was bad.
Repair Cost Estimate
DIY Repair
Parts only
$50-$250
Shop Repair
Parts + labor
$150-$500
Save $100-$250 by doing it yourself
Difficulty
intermediate
Time
1-3 hours
Intermediate - requires basic mechanical skills and a multimeter for electrical testing. Access to the EGR valve can be challenging on some vehicles.
Cost of Waiting
Ignoring P0405 leads to increased emissions, reduced fuel economy, and potential engine pinging or knocking. A $100-$250 EGR valve replacement now prevents long-term engine damage from detonation or failing an emissions test.
While You're In There...
The EGR gasket is removed during EGR valve replacement and should always be replaced to ensure a proper, leak-free seal.
If removing the EGR valve, it's a good opportunity to clean the throttle body for improved airflow and engine performance.
Tools You'll Need
- Basic hand tools (sockets, wrenches)
- Multimeter
- Scan tool (optional, but helpful for live data)
- Vacuum pump (for testing vacuum-operated EGR valves)
- Wire brush and carburetor cleaner (for carbon cleanup)
P0405 is a common emissions system code. While it affects performance and emissions, it's usually a straightforward repair involving the EGR valve, which is a replaceable component.
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Your Next Steps
Step 1: Visually inspect the EGR valve, its electrical connector, and all vacuum lines for any obvious damage or disconnections.
Step 2: If visual inspection doesn't reveal the issue, use a multimeter to test the voltage at the EGR sensor connector. Look for proper reference voltage and a signal that changes when the EGR valve is commanded open (if possible with a scan tool).
Step 3: Parts you'll likely need: A new EGR valve (which often includes the sensor) and a new EGR gasket.