Powertrain, generic · Auxiliary emission controls
P0490 EGR A Control Circuit High
Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo
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.
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
Symptoms
- Check engine light on
- EGR switched off, usually no noticeable change
- Higher NOx
Repair estimate
DifficultyMediumDIY possible
Parts and labour€50–700
Time0.5–3 h
Typical range across vehicles; the real cost depends on what the testing finds.
Parts involved
egr valveegr valve actuatoregr wiringengine control module
Related codes
References: gsi.ext.gm.com, gsi.ext.gm.com, fordservicecontent.com, saabwisonline.com.