What P046D means
Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx.
How the engine computer detects it
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. P046D means brief excursions of sensor A out of its valid range, too short for P0405/P0406. Ford gasoline engines from 2020 set it when the position signal stays above 95 % or below 5 % of its range for just 0.4 s, whereas 4 s set P0405/P0406; the check runs continuously during the EGR monitor above 8.25 V and 400 rpm. EGR is then switched off.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light on, may come and go
- Usually no noticeable change
- Occasional jerking when EGR switches off
Common causes
- Loose contact or corrosion at the EGR valve connector Most likely
- Chafed wire with brief short to ground or positive Possible
- Position sensor in the valve worn Possible
- Disturbed 5 V reference Less likely
How to diagnose P046D
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: egr valve position sensor, egr valve, sensor wiring, engine control module.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 4
- Auxiliary emission controls
- 6D
- Specific fault
Questions drivers ask
Can I drive with code P046D?
Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.
Will my car pass an emissions inspection with P046D?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P046D clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
Can I fix P046D myself?
Often yes, with an OBD-II scanner and basic tools. Difficulty: easy. Start with the cheapest checks before replacing expensive parts.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.