# P0403: Exhaust Gas Recirculation "A" Control Circuit **Verdict:** Safe to drive Emissions - Generic OBD-II code, applies to all gasoline cars and light trucks sold in the US since 1996. - **Typical cost:** $100-$750 - **Urgency:** Keep driving - **Most likely:** Failed EGR valve/solenoid or wiring - **DIY?:** Steps 1-3 ## Quick answer P0403 means the engine computer has found an electrical problem in the circuit it uses to control the exhaust gas recirculation (EGR) valve or EGR control solenoid. This is a wiring or electrical part fault, not a flow problem. A failed valve or solenoid coil, a damaged connector, or broken wiring is usually to blame. ## What does P0403 mean? The engine computer controls EGR in one of two ways. On older cars it switches a solenoid that sends engine vacuum to a vacuum-operated valve. On most newer cars it powers a small electric motor or solenoid built into the EGR valve itself. Either way, the computer is driving an electrical circuit made up of a power feed, the coil or motor, and a control wire back to the computer. P0403 is a circuit code. The computer constantly checks that the voltage on the control wire matches what it is commanding, and sets the code when it sees an open circuit, a short, or a reading out of range. Because this check does not need a special test drive, some cars set the code on the first trip it is detected, while others wait for a second. It says nothing about how much exhaust is flowing, and it does not prove the valve is bad. Names vary, too: some makers call the part the EGR solenoid or vacuum regulator. ## What are the symptoms of P0403? - Check engine light on - Usually no change in how the car drives - Pinging under load on some engines - Failed emissions test ## What causes P0403? Ranked from most to least likely. Check them in this order: the cheap, common causes first. 1. **Failed EGR valve or solenoid coil** (most common). The coil or motor inside the EGR valve or control solenoid can open or short after years of heat cycles, and this is the most common reason for P0403. A resistance check across the part's terminals usually reveals it, and a reading far from specification, or no continuity at all, confirms the part has failed internally. 2. **Damaged connector or wiring** (common). The EGR harness runs near hot exhaust parts, so insulation can melt, wires can break where they flex, and connector pins can corrode or loosen. Look for brittle, discolored, or oil-soaked wiring near the valve. Wiggling the harness with the engine running while watching for the code to reset is a simple way to find an intermittent break. 3. **Blown fuse or loss of power feed** (less common). The EGR valve or solenoid gets power through a fuse that is often shared with other engine parts such as injectors, coils, or other solenoids. If that fuse blows, several circuit codes usually appear at once. A blown fuse means something on that circuit drew too much current, so replacing the fuse alone may not last. 4. **Engine computer driver fault** (rare). The engine computer switches the EGR circuit with an internal transistor called a driver. A shorted solenoid or wire can damage that driver, so a computer fault sometimes follows a failed part. This is rare and should only be suspected after the part, the wiring, and the power feed have all tested good with a meter. ## How do you diagnose P0403? 1. Read the code and check for other circuit codes that share the same fuse or power feed. 2. Inspect the EGR connector and harness for melting, corrosion, or loose pins. 3. Measure the valve or solenoid resistance and compare with specification. 4. Check for power at the connector with the key on and confirm the computer's control signal with a test light or scope. ## How do you fix P0403, and what does it cost? | Fix | Typical cost | What it involves | | --- | --- | --- | | Repair EGR wiring or connector | $100-$300 | Fixes melted, broken, or corroded wires and pins. | | Replace EGR control solenoid | $100-$300 | For systems where a separate solenoid controls a vacuum-operated valve. | | Replace electronic EGR valve | $250-$750 | Needed when the motor or coil is built into the valve and has failed. | ## Is it safe to drive with P0403? > **Safe to drive.** It is usually safe to drive while you arrange a repair. The car may ping under heavy load and will likely fail emissions testing until fixed. ## Will P0403 fail an emissions test? A car with P0403 stored and the check engine light on will fail an OBD-based emissions test in most states. Because the computer cannot properly control EGR, the EGR monitor may also stay incomplete. On tailpipe tests the car may show high NOx if the valve never opens. Fix the circuit before going back for a retest. ## After the repair: clearing P0403 After repairing the wiring or replacing the part, clear the code and run the engine. Many circuit faults return within minutes if the problem is still there, so a code that stays away through a test drive is a good sign. Then drive normally for a few days until the EGR monitor shows ready on a scan tool. ## How to prevent P0403 - Keep the EGR connector clipped in place and away from exhaust heat when other engine work is done. - Ask shops to re-secure any harness clips they remove near the exhaust manifold or turbocharger. - Fix oil and coolant leaks that drip on the EGR wiring and soften its insulation over time. - Look for rodent damage under the hood if the car sits outdoors for long periods. - Have a corroded EGR connector cleaned and sealed properly rather than just wiggled back into place. ## Codes often seen with P0403 - [P0400](/codes/p0400): Exhaust Gas Recirculation "A" Flow - [P0401](/codes/p0401): Exhaust Gas Recirculation "A" Flow Insufficient Detected - [P0402](/codes/p0402): Exhaust Gas Recirculation "A" Flow Excessive Detected ## Frequently asked questions ### Can I drive with a P0403 code? Yes, P0403 rarely affects how the car drives right away, and most drivers notice only the check engine light. Get it fixed before your next emissions test, and sooner if you hear pinging under load, since that means the engine is running without the EGR flow it was designed for. ### Is P0403 a bad EGR valve? It can be, but P0403 only says the control circuit has a fault. A failed coil inside the valve or solenoid is the most common cause, yet wiring and connectors are close behind. Test resistance, power, and the control signal before buying a valve that may not fix the problem. ### How do I test for P0403 at home? With a basic multimeter you can check the EGR valve or solenoid resistance and look for power at the connector with the key on. Compare the readings with the specifications for your vehicle in a service manual. Also inspect the connector for corrosion and the harness for melted or rubbed-through spots. ### How much does it cost to fix P0403? Most P0403 repairs cost $100 to $750 at an independent shop. Wiring repair or a separate vacuum control solenoid usually costs $100 to $300. An electronic EGR valve with a built-in motor costs $250 to $750, depending on the vehicle and how hard the valve is to reach. ### Will P0403 make me fail an emissions test? Yes, P0403 will cause a failed OBD-based emissions test in most states while the code is stored and the light is on. The EGR monitor may also stay incomplete because the computer cannot run its flow test. Repair the circuit, then drive until the monitors show ready before retesting. ### Can I fix P0403 myself? Many owners can fix P0403 if the cause is a corroded connector, a blown fuse, or an easy-to-reach solenoid. You need a multimeter and a wiring diagram for your vehicle. Intermittent wiring faults, valves buried under the intake, and computer driver checks usually need a shop with a scope and service information. ### Can a blown fuse cause P0403? Yes, if the fuse that powers the EGR valve or solenoid blows, the computer sees an open circuit and sets P0403. You will often see other circuit codes at the same time because the fuse is shared. Find out why it blew, since a shorted part or wire can blow the new fuse too. ### What is the difference between P0403 and P0401? P0403 is an electrical fault in the EGR control circuit, while P0401 means the EGR system works electrically but flow is too low. With P0403 the computer cannot properly command the valve at all. Fixing the circuit sometimes clears both codes, since a valve that is not powered cannot flow either. ### Will P0403 go away if I clear it? Clearing the code turns off the light only until the computer checks the circuit again, which can happen within one drive. A loose connector can make the code come and go for weeks. If it keeps returning, the circuit fault is still there and needs to be traced with a meter. ### Why did P0403 come back after I replaced the EGR valve? It usually comes back because the real problem is wiring, a connector, or a fuse, so a new valve cannot fix it. A wrong part number or a poor-quality valve can also cause it. Check power, ground, and the control signal at the connector before and after installing the new part. ## Sources - [SAE J2012: Diagnostic Trouble Code Definitions](https://www.sae.org/standards/content/j2012_201812/) ## Other emissions codes - [P0400 Exhaust Gas Recirculation "A" Flow](https://diagxcar.com/codes/p0400) - [P0401 Exhaust Gas Recirculation "A" Flow Insufficient Detected](https://diagxcar.com/codes/p0401) - [P0402 Exhaust Gas Recirculation "A" Flow Excessive Detected](https://diagxcar.com/codes/p0402) - [P0404 Exhaust Gas Recirculation "A" Control Circuit Range/Performance](https://diagxcar.com/codes/p0404) - [P0405 Exhaust Gas Recirculation Sensor "A" Circuit Low](https://diagxcar.com/codes/p0405) - [P0406 Exhaust Gas Recirculation Sensor "A" Circuit High](https://diagxcar.com/codes/p0406) - [P0410 Secondary Air Injection System "A"](https://diagxcar.com/codes/p0410) - [P0411 Secondary Air Injection System "A" Incorrect Flow Detected](https://diagxcar.com/codes/p0411) - [P0420 Catalyst System Efficiency Below Threshold (Bank 1)](https://diagxcar.com/codes/p0420) - [P0421 Warm Up Catalyst Efficiency Below Threshold (Bank 1)](https://diagxcar.com/codes/p0421) ## Repair costs - [EGR valve replacement cost](https://diagxcar.com/cost/egr-valve-replacement) --- Source page: https://diagxcar.com/codes/p0403 Updated: 2026-11-03 General information, not a substitute for a qualified mechanic.