P0490Generic code

P0490 Code: Exhaust Gas Recirculation Control Circuit High

The P0490 code indicates high voltage in the control circuit of the EGR valve, from an open circuit or a short to voltage. Expect an unstable idle, stalling when you stop and pinging under load. Carbon is the number one mechanical problem.

Severity
Medium
Can I keep driving?
Yes, but with caution
Estimated cost
$80 to $600
Difficulty
Medium
System
Emissions Control
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0490 code means

The computer controls how far the EGR valve opens with a vacuum solenoid or an electric motor. That is how it regulates how much exhaust gas goes back into the intake, depending on load and temperature.

The computer monitors the control circuit from its own driver transistor. The P0490 code indicates high voltage in the control circuit (an open circuit or a short to voltage). Before replacing the component, check the fuse, relay, connector and wiring, since they are the most common cause.

If the valve does not obey, two things can happen: it can stick closed (pinging under load, high NOx) or stick open (unstable idle, hesitation, the engine stalls when you stop). Carbon on the valve seat is the most frequent mechanical cause.

To confirm it, measure the continuity of each wire between the component connector and the computer connector with the key off. It should be less than 1 ohm, and an infinite reading means the wire is open. If the wiring is good, measure the component itself: infinite resistance confirms it is open inside.

P0490 code symptoms

  • Check engine light on.
  • Unstable idle, or the engine stalls when you stop.
  • Pinging when accelerating under load.
  • Loss of power (diesel).

Likely causes of the P0490 code

  1. Connector loose or broken. The most frequent cause, especially after another repair in the area.
  2. Open coil or motor, with infinite resistance in the component.
  3. Control wire cut between the component and the computer.
  4. Short to 12 V, where the control wire touches another wire that carries voltage.

How to diagnose the P0490 code step by step

  1. Command the component with the scan tool and check whether it responds.
  2. Check the fuse and relay.
  3. Measure the supply at the connector: battery voltage with the key on or when it is commanded.
  4. Measure the component resistance and compare it with the manual. Also check the insulation to ground.
  5. Check the control wire for continuity and for shorts.
  6. Command the EGR with the scan tool. At idle the engine should stumble if the valve opens and the passages are clean.
  7. Remove and clean the valve and check the EGR passages.

How to fix the P0490 code

  • Repair the connector, the wiring or the power supply.
  • Replace the EGR valve if it does not respond with correct power and control.
  • Clear the codes and verify that the monitor completes.

Technical reference data

  • Solenoid or control motor: 12 V with PWM control.
  • Approximate solenoid resistance: 10 to 30 ohms.
  • Approximate values only: check the manufacturer data for your engine.

Brand-specific notes

Carbon is the number one problem on diesels and on many GDI engines.

P0490 on Volkswagen TDI

Carbon buildup is the leading problem on Volkswagen TDI engines.

P0490 on Ford TDCi

Carbon buildup is the leading problem on Ford TDCi engines.

P0490 on Toyota D-4D

Carbon buildup is the leading problem on Toyota D-4D engines.

Frequently asked questions about P0490

Can I drive with a P0490 code?
With caution, and keep an eye on engine temperature and power. A P0490 code can bring a rough idle or stalling when you stop.
What does the EGR valve do?
The computer controls how far the EGR valve opens with a vacuum solenoid or an electric motor. That regulates how much exhaust gas returns to the intake depending on load and temperature.
Do I always have to replace the part?
No. Check the fuses, relays, connectors and wiring first.
How much does it cost to fix P0490?
Roughly $80 to $600, depending on whether it is wiring, a cleaning job or the valve itself.
What does the P0490 code mean?
It is a generic OBD2 code that means the EGR valve control circuit is reading high voltage, from an open circuit or a short to voltage.
What is the most common cause of P0490?
A loose or broken connector, especially after another repair in the area. An open coil or motor and a cut control wire come next.

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