P0490
Exhaust Gas Recirculation A Control Circuit HighP0490 is a generic OBD-II powertrain diagnostic trouble code: Exhaust Gas Recirculation A Control Circuit High. It is logged by the engine control unit when the egr monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0490 means
P0490 is a generic SAE OBD-II diagnostic trouble code defined as Exhaust Gas Recirculation (EGR) Vacuum Regulator Solenoid Control Circuit High. It is set when the powertrain control module (PCM) detects an abnormally high voltage signal on the EGR vacuum regulator solenoid control circuit — typically above the expected duty-cycle or reference voltage range. The EGR system recirculates a metered portion of exhaust gas back into the intake manifold to lower peak combustion temperatures and reduce nitrogen oxide (NOx) emissions. The vacuum regulator solenoid modulates the vacuum supply to the EGR valve in response to PCM commands; a circuit high fault means the PCM cannot pull the control line low as commanded, pointing to an open circuit, a short to battery voltage, or a failed solenoid driver.
Unlike a mechanical EGR fault (P0400–P0408 range), P0490 is purely electrical in nature. The most frequent root causes are damaged, corroded, or disconnected wiring and connector terminals at the solenoid harness plug, although a failed solenoid winding or, in rare cases, a faulty PCM driver stage can produce the same high-voltage reading.
When P0490 is active the PCM typically illuminates the malfunction indicator lamp (MIL) and may default EGR to a fixed or disabled state. This can result in increased NOx emissions, rough idle, reduced low-speed torque, and marginally higher fuel consumption.
Common causes
Most-frequently reported root causes when P0490 is logged.
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1
Open circuit in the EGR vacuum regulator solenoid control wiring (broken wire or loose terminal)
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2
Short to battery positive voltage on the solenoid control circuit
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3
Corroded, burnt, or water-damaged harness connector at the EGR solenoid
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4
Failed EGR vacuum regulator solenoid (open or high-resistance winding)
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5
Carbon buildup causing solenoid plunger to stick, overloading the driver circuit
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6
Faulty PCM solenoid output driver stage (rare — rule out all external causes first)
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7
Damaged vacuum lines causing back-pressure that stresses solenoid operation
Symptoms drivers notice
How to diagnose P0490
A typical diagnostic flow when this code is present.
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1
Connect a scan tool, record all stored DTCs and freeze-frame data
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2
Visually inspect the EGR vacuum regulator solenoid harness connector and wiring for corrosion, burnt insulation, pulled-back terminals, or obvious breaks
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3
With the ignition OFF, disconnect the solenoid connector and measure solenoid winding resistance; compare to manufacturer specification
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4
With the ignition ON (engine OFF), back-probe the control wire at the solenoid connector and measure voltage
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5
Command the EGR solenoid ON/OFF via the scan tool's bidirectional controls and verify the control circuit voltage toggles correctly
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6
Inspect vacuum lines connected to the solenoid for cracks, kinks, or disconnections and repair as needed before re-testing
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7
Clear codes, perform a road test drive cycle, and confirm no reoccurrence
Vehicles where we've handled P0490
Platforms in our catalogue with confirmed P0490 coverage.
Related powertrain codes
- P0400 — Exhaust Gas Recirculation Flow Malfunction
- P0401 — Exhaust Gas Recirculation Flow Insufficient Detected
- P0402 — Exhaust Gas Recirculation Flow Excessive Detected
- P0403 — Exhaust Gas Recirculation Circuit Malfunction
- P0404 — Exhaust Gas Recirculation Circuit Range/Performance
- P0405 — Exhaust Gas Recirculation Sensor A Circuit Low
Frequently asked questions
Can I drive with a P0490 code?
The vehicle is usually driveable since P0490 is an electrical circuit fault rather than a catastrophic failure. However, the EGR system may be disabled by the PCM, leading to increased NOx emissions, rough idle, and slightly higher fuel use.
Is P0490 the same as P0489?
No. P0489 is the companion 'circuit low' code, set when the PCM detects abnormally low voltage on the EGR vacuum regulator solenoid control circuit. P0490 specifically indicates a high-voltage condition — typically an open circuit or short to battery positive.
Will cleaning the EGR valve fix P0490?
Cleaning the EGR valve may resolve a sticking plunger that was overloading the solenoid driver, but P0490 is fundamentally an electrical fault. Always diagnose the wiring and solenoid resistance first.
How much does it typically cost to repair P0490?
A replacement EGR vacuum regulator solenoid typically costs $40–$150 in parts, with 0.5–1.5 hours of labour. Wiring repairs vary widely. PCM replacement is the most expensive scenario but is rare.
Disabling P0490 in software
RaceTune can permanently disable P0490 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
ECUs with a P0490 disable in our catalogue
Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.
- Bosch EDC16C31 verified 1 software version
- Bosch EDC17C50 verified 1 software version
- Bosch EDC17C74 verified 1 software version
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
Got P0490 in your scan?
Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.
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