Emissions control: EGR, DPF, catalytic converter and AdBlueGeneric OBD-II codeUrgency: Garage soon
Code P0490: EGR control circuit: voltage too high
P0490 means: exhaust gas recirculation (EGR): control circuit "A" high.[1][2][3][4] P0490 indicates an electrical fault in the circuit that drives the EGR valve: the ECU reads a higher voltage in it than expected. According to AutoDTCs it may be an open circuit, a short to voltage or a failure of the valve driver on the control wire; TAT describes it as a voltage higher than expected in the EGR valve control circuit ("circuit A").[1][2][3]
What code P0490 means
P0490 indicates an electrical fault in the circuit that drives the EGR valve: the ECU reads a higher voltage in it than expected. According to AutoDTCs it may be an open circuit, a short to voltage or a failure of the valve driver on the control wire; TAT describes it as a voltage higher than expected in the EGR valve control circuit ("circuit A").[1][2][3]
It is a fault in the control circuit (the part that operates the valve), not in the feedback sensor or the gas flow. In a control circuit like this one, "high" means the line stays at voltage when the ECU has commanded it to earth: there is a break in the control wire or the earth, or a short to voltage.[3][5]
In the workshop manual for the 2011 diesel Saab 9-5, the ECU drives the EGR valve through its solenoid valve: it receives a reference voltage and the ECU controls it by connecting the control circuit to earth. P0490 is stored when, with EGR commanded, the ECU detects a short to voltage in the EGR motor control circuit (the manual describes it as "short to battery" or "high input").[6]
Its partner is P0489, which is the same circuit but with the signal low (short to earth).[1][4][6]
It is a generic OBD-II code (it starts with P0), so it means the same on any make; what changes from one engine to another is the most likely cause.[2][7]
Original definition (SAE J2012): Exhaust Gas Recirculation "A" Control Circuit High[1][2][3][4]
Codes from the same family
They indicate the same problem in a specific cylinder, bank or sensor. Causes, symptoms and diagnosis are those on this page.
- P0490Exhaust gas recirculation (EGR): control circuit "A" high.
- P0489Exhaust gas recirculation (EGR): control circuit "A" low. It is the partner of P0490: the same valve control circuit, but with the voltage below what is expected. In the Saab workshop manual it is described as a short to earth of the EGR motor control circuit, and AutoDTCs points to it as an electrical fault of the control circuit, not of the position sensor.[4][6][8][9]
Causes of P0490 and its family
From most to least likely, according to the sources.
- 1Damaged wiring or connector: open circuit between the ECU and the valve, control wire shorted to voltage, corroded terminals or terminals pushed out of the connector, or a harness chafed near the valve or the exhaust manifold.[1][2][3][6]
- 2Faulty EGR valve: open solenoid or valve motor winding, or a stuck valve. In Saab's procedure, if the circuits are fine, the valve is replaced.[1][2][3][6]
- 3Loss of power supply to the valve.[3]
- 4Damaged EGR driver inside the ECU: AutoDTCs and Saab leave it until last, once the wiring and the valve have been ruled out.[2][3][6]
- 5On pneumatically operated EGR valves, a faulty vacuum solenoid valve or a broken vacuum hose.[1]
Symptoms
- Engine warning light on.[1][3]Engine warning light: faults that cause it
- Somewhat rough idle or uneven engine running.[1][3]Vibrations: faults that cause it
- Less power and poorer engine performance.[1][2]Less power: faults that cause it
- Hard starting.[1]Hard to start: faults that cause it
- Higher fuel consumption.[1]Uses more fuel: faults that cause it
- EGR is disabled and the valve does not respond to commands from the diagnostic tool.[3]
- Slight knocking under load, because of the higher combustion temperature when gases are not recirculated.[3]
- More NOx and emissions: likely failure of the emissions test until repaired.[2][3]
- Often there is hardly any noticeable change when driving.[3]
How to diagnose P0490
In order: from the most likely and cheapest to check to the most expensive.
- 1Read the code, the associated codes (for example P0489 or P0403) and the freeze-frame data with a diagnostic tool to confirm the fault.[3]
- 2Command the valve with the diagnostic tool and check whether it responds; if you can, watch the signal in the control circuit at the same time. PartsAvatar also recommends comparing the EGR's operation with the manufacturer's specifications.[1][3]
- 3Inspect the connector and the valve: corrosion, loose terminals or terminals pushed out of the connector, and harness damage, especially near the exhaust manifold.[3]
- 4With the ignition on, check that the valve is receiving power.[3]
- 5With the valve and the ECU unplugged, check the control circuit: continuity (open circuit) and absence of a short to voltage, following the manufacturer's values. The Saab manual for the diesel 9-5 measures the resistance of the reference line to earth and to the ECU, and the voltage of the control line with the ignition on; those values are specific to that car.[3][5][6]
- 6Measure the resistance of the valve winding or motor and compare it with the specification.[3][5]
- 7On a pneumatically operated EGR valve, disconnect the vacuum hose and apply vacuum with a hand pump to see whether the valve moves.[1]
- 8Replace the valve only if it fails when it has correct power and earth. If the code returns with everything in order, check the ECU driver: it is the last thing to be ruled out.[3][5][6]
Can I keep driving with P0490?
Garage soon
Only one source gives an explicit assessment. AutoDTCs says you can normally keep driving, but that the EGR is usually disabled, with possible slight knocking under load, somewhat rough idle and a likely failure of the emissions test until repaired; it recommends repairing it before the inspection or before demanding use. TAT mentions poorer engine performance and more emissions, and PartsAvatar, less power and more consumption. None of the sources consulted mentions an immediate risk.[1][2][3]
Documented faults related to P0490
Known faults of specific engines and cars, with their repair cost, the affected years and their sources.
EGR valve: the most serious faults by engine and car
- Critical severityFrequency: Very frequentBMW B47EGR cooler leaks with risk of engine fireYes: the EGR valve cooler can suffer internal coolant leaks which, mixed with soot and oil, can reach combustion temperatures; BMW has launched several technical campaigns since 2018 to inspect and replace it because of the risk of engine fire.Repair (garage): €500–€1,500
- Critical severityFrequency: Very frequentBMW N57EGR cooler leaks with risk of engine fireYes: like the N47 and B47, the N57 is covered by BMW's service campaign for EGR cooler leaks, which can mix coolant with soot and oil to combustion temperatures. BMW checks free of charge the 6-cylinder engines built between July 2012 and June 2015 because of the fire risk.
- High severityFrequency: Very frequentOM651EGR and particulate filter clogging, and emissions software updatesThe particulate filter and EGR clog up with short journeys, as on any diesel with these systems. In addition, Germany's KBA required software updates on several models with this engine between 2018 and 2021 because of a function that reduced EGR outside a temperature range.Repair (garage): €800–€2,500
- Medium severityFrequency: Very frequentOM642Emissions defeat device (AdBlue/EGR) and software update campaignGermany's KBA found indications of emissions manipulation in cars with the OM642 engine (alongside the OM651): AdBlue dosing and the EGR changed between the test bench and the road. Mercedes-Benz denied it, but in 2018 it recalled hundreds of thousands of diesels in Europe.
Wiring, connectors and short circuits: the most serious faults by engine and car
- Critical severityFrequency: OccasionalBMW N62 / N63Additional turbo coolant pump with a risk of short circuit and fireIn 2011 BMW recalled 5, 6 and 7 Series, X5 and X6 models built between 2007 and 2011 because of the additional turbo coolant pump: moisture, a short circuit and, in extreme cases, a fire. In 2012 there was another campaign for a crack in the pump, with a more robust version.
- High severityFrequency: Occasional1.3 TCeBlown fuel pump fuseOn the Renault Captur II and Clio V with the 1.3 TCe engine, a 20-amp fuse can blow and leave the car without an engine. According to L'argus, in April 2021 this fault still had no factory fix; the official service centre's diagnosis includes checking, and sometimes replacing, the catalytic converter.
- High severityFrequency: OccasionalM264/M254Poorly tightened 48 V earth wiring in the mild-hybrid system (fire risk)Mercedes-Benz has issued several recalls (2022-2025) because the 12 V and 48 V earth connections of some cars with a 48 V system may be poorly tightened: resistance rises, the connection heats up and a fire cannot be ruled out. The official workshop checks them and repairs them if necessary in an hour or more.
- High severityFrequency: Occasional1.9 TDIUnit injector tappet wear and injector wiring damageOn the unit injector system, the tappets that operate the injectors can wear if the oil is not changed on time, and the injector wiring can be damaged by contact with oil, causing misfires or loss of power.
- Critical severityFrequency: CommonRover 75Seat SRS connector fault with airbag and seatbelt warning light onAuto Express warns that the Rover 75's seat SRS connector can cause the airbags to fail, and dealers were fixing it with revised connectors. The Dutch APK inspection puts the airbag or seatbelt fault warning among the most frequent defects across almost all series.
- Critical severityFrequency: OccasionalAlfa Romeo GiuliettaShort circuit from badly routed wiring that can prevent gear shifting (KBA campaign, 2010-2015)Yes: according to Germany's KBA, on Alfa Romeo Giulietta cars built between 2010 and 2015 inadequate cable routing could cause a short circuit and, as a result, gear-shift failure.
Frequently asked questions
What is the difference between P0490, P0489 and P0403?
All three are electrical faults in the circuit that drives the EGR valve. P0489 and P0490 are partners: the first is the "low" control circuit (short to earth) and the second the "high" one (short to voltage). P0403 is the general EGR control circuit fault; in the Saab manual, with the descriptor "control circuit open", and all three share the same diagnostic procedure. P0401 and P0402, on the other hand, are flow codes and usually have a mechanical cause, and P0405 and P0406 affect the position sensor.[4][6][10]
Can I drive with code P0490?
Normally yes, but it should be repaired soon. AutoDTCs says the car can usually still be driven, although the EGR is disabled and slight knocking under load, a somewhat rough idle and a likely emissions test failure may appear; it advises repairing it before the inspection or before demanding use, such as towing. The other sources do not assess urgency.[1][2][3]
Does the EGR valve need replacing when P0490 appears?
Not necessarily. The code refers to the control circuit: before replacing the valve you have to check the power supply, the earth and the wiring to the ECU, and measure the winding resistance. AutoDTCs recommends replacing the actuator only if it fails when it has correct power and earth, and the Saab procedure leaves the valve until after the circuits and the ECU until last.[3][5][6]
Can you notice P0490 when driving?
Often hardly at all. AutoDTCs notes that driving normally changes little, even though the EGR is disabled; PartsAvatar, on the other hand, mentions uneven running, hard starting, less power and more consumption. In both cases the main warning is the engine warning light.[1][3]
Will I pass the ITV with P0490 active?
If the code keeps the engine warning light on, no: according to Diariomotor, that light is a serious defect at the ITV (Spain's roadworthiness inspection, similar to the MOT) and, on Euro 5 and Euro 6 cars, the inspection also reads the OBD system. In addition, AutoDTCs warns that failing the emissions test is likely until it is repaired.[3][11]
Not sure what is wrong with your car? Describe what you notice in the symptom diagnosis or see all fault codes.
Sources
Every fact on this page links to its source. If you find an error, let us know.
- P0490 - OBD Trouble CodePartsAvatar · Technical documentation · published 14 March 2023 · consulted 2 October 2026
- P0490: EGR valve Circuit high Circuit AThe Automotive Technician (TaT) · Technical documentation · consulted 2 October 2026
- P0490 – Exhaust Gas Recirculation Control Circuit HighAutoDTCs · Technical documentation · published August 2026 · consulted 2 October 2026
- Generic OBDII P Codes P0400-P0499Rick's Free Auto Repair Advice · Other source · published 16 March 2024 · consulted 2 October 2026
- How to Test a Solenoid or Actuator Control CircuitAutoDTCs · Technical documentation · consulted 2 October 2026
- DTC P0403, P0489, or P0490 — SAAB 9-5 (9650) 2011, 4-cylinder dieselSAAB Workshop Information System Online · Technical documentation · consulted 2 October 2026
- On-board diagnosticsWikipedia · Other source · consulted 2 October 2026
- P0489 - EGR valve Circuit low Circuit A | TaTThe Automotive Technician (TaT) · Technical documentation · consulted 4 October 2026
- P0489 – Exhaust Gas Recirculation Control Circuit LowAutoDTCs · Technical documentation · published August 2026 · consulted 4 October 2026
- How to Diagnose EGR System Codes (P0401, P0402, P0403, P0406)AutoDTCs · Technical documentation · consulted 2 October 2026
- Desmontando mitos: ¿puede pasar mi coche la ITV con el testigo de «avería motor» encendido?Diariomotor · Motoring press · published 8 March 2021 · consulted 2 October 2026 · in Spanish