Powertrain, generic · Auxiliary emission controls
P0407 EGR Sensor B Circuit Low
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. What EGR sensor B is depends on the manufacturer – on systems with a second valve or pressure sensor it is that second sensor. GM's diesels of 2017/18 use P0407 for the coolant temperature sensor at the inlet of the high-pressure EGR cooler: low means a resistance below 55 Ω, i.e. very hot or shorted to ground, MIL after two trips. No manufacturer document available to us uses the code for a second position sensor. A substitute value is used.
Likely causes
Sensor wire shorted to ground
Sensor faulty
Connector corroded (near coolant or exhaust)
Engine module input
Symptoms
- Check engine light on
- Usually no change in driving
- EGR or EGR cooler protection possibly restricted
Repair estimate
DifficultyEasyDIY possible
Parts and labour€30–250
Time0.5–1.5 h
Typical range across vehicles; the real cost depends on what the testing finds.
Parts involved
egr sensor begr cooler coolant temperature sensorsensor wiringengine control module
Related codes
References: gsi.ext.gm.com, gsi.ext.gm.com, law.cornell.edu.