P0407 code meaning
EGR Sensor B Circuit Low
Powertrain system Generic code P04xx codes Check engine light
What P0407 means
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.
P0407 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.5 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0407
- Check engine light on
- Usually no change in driving
- EGR or EGR cooler protection possibly restricted
Common causes of P0407
- Most likelySensor wire shorted to ground
- PossibleSensor faulty
- PossibleConnector corroded (near coolant or exhaust)
- Less likelyEngine module input
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
EGR sensor bEGR cooler coolant temperature sensorSensor wiringEngine control module
What each part of P0407 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 07 | The exact fault in that area. |
What to do next
- Note P0407 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0407
What does P0407 mean?
P0407 means "EGR Sensor B Circuit Low". Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. It is a generic code, so it means the same on every make.
Is it safe to drive with P0407?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0407 fail an emissions test?
Yes, it can. P0407 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0407 to fix?
Difficulty: easy. A typical repair takes 0.5 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0407 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.