P046F code meaning
EGR Sensor B Circuit Intermittent/Erratic
Powertrain system Generic code P04xx codes Check engine light
What P046F means
Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. Which part EGR sensors A and B are depends on the maker: sensor A is usually the position sensor of EGR valve A; GM's Duramax diesels of 2017/18 use sensor B for the coolant temperature sensor at the inlet of the high-pressure EGR cooler, FCA for the position sensor of the low-pressure valve. P046F means jumps or dropouts of sensor B. GM's Duramax diesels set it when the value leaves a narrowing window around the last valid reading – 40 of 50 samples of 100 ms, MIL after two trips. A substitute value is then used and EGR cooler monitoring is suspended. Usually a loose contact or broken wire is the cause.
P046F at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P046F
- Check engine light on, may come and go
- Usually no change in driving
Common causes of P046F
- Most likelyLoose contact at the sensor connector
- PossibleChafed wire or vibration break
- PossibleSensor faulty internally
- Less likelyEngine module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
EGR sensor bSensor wiringEngine control module
What each part of P046F 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). |
| 6F | The exact fault in that area. |
What to do next
- Note P046F 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 P046F
What does P046F mean?
P046F means "EGR Sensor B Circuit Intermittent/Erratic". 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 P046F?
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 P046F fail an emissions test?
Yes, it can. P046F 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 P046F to fix?
Difficulty: easy. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P046F 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.