P0490: EGR A Control Circuit High

Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. P0490 means the drive circuit of EGR valve A is shorted to battery voltage, or its output stage sees overcurrent. GM's Duramax LML sets it at 0.5 Ω or less to the supply for 3 s, GM's 2017 diesels at an H-bridge current above 8 A (160 of 200 samples), Ford diesels after 0.35 s – MIL after two trips. The output stage switches off for protection and the valve falls into its spring position, closed; EGR is off.

Medium severity. Can I keep driving?You can normally drive in moderation, but get it repaired soon: if the valve is stuck open, the engine may idle very poorly.

Symptoms

Check engine light on
EGR switched off, usually no noticeable change
Higher NOx

Most likely causes

Harness shorted to a supply wire (chafing)
EGR valve with shorted turns (low resistance, overcurrent)
Moisture in the connector
Driver in the engine module

What to check, in order

Start with the simplest. You can tick off each step.

Check the connector and any vacuum hoses
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Use live data to compare the commanded opening with the actual opening
Clean the valve and passages if they are clogged with carbon
Test the actuator with the scanner
Replace the valve if it still does not follow the command after cleaning

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P0490 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
4: Emissions
90: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0490?

You can normally drive in moderation, but get it repaired soon: if the valve is stuck open, the engine may idle very poorly.

What causes code P0490?

The most common causes are: harness shorted to a supply wire (chafing); eGR valve with shorted turns (low resistance, overcurrent); moisture in the connector.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.