What it means
EGR B drive line stuck low — short to ground. EGR mixes inert exhaust into intake to lower combustion peak temperature — too little raises NOx, too much causes misfires and rough running.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
EGR control B drives the valve in the engine’s second exhaust-gas-recirculation path, where fitted. P045C sets when the module detects that the B control circuit signal is lower than expected, commonly because the control wire is shorted to ground or has a poor connection.
Common causes
Most likely first.
- Short to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light on
- Pinging or knocking under load
- Power loss and hesitation
- Possible rough idle
- Failed emissions inspection (NOx)
How to diagnose it
- Review freeze-frame data and related EGR codes to confirm the fault is on control B and determine when it becomes active.
- Inspect the EGR B connector and harness for chafing, pinched insulation, water intrusion, corrosion, or terminals pushed out of position.
- Monitor EGR B circuit data while gently moving accessible harness sections to see whether the low signal changes.
- Disconnect components as directed by the wiring diagram and test the EGR B control wire for a short to ground.
- Check connector contact quality and circuit continuity, then compare measurements with the manufacturer's specification.
- If the short and connection faults are ruled out, verify the control module output and grounds using the manufacturer's diagnostic procedure.
Common fixes
- Repair chafed EGR B wiring that is contacting ground.
- Clean or repair corroded, loose, or pushed-back terminals at the EGR B connector.
- Replace a failed EGR B solenoid or valve if it is internally shorted and the wiring is sound.
- Repair a control module fault only after confirming the B circuit and its connections meet specification.
Can I keep driving?
If the engine runs smoothly, gentle driving may be possible, but stop putting it under heavy load if it pings, hesitates, or loses power. The low control signal can prevent correct EGR operation, increase NOx emissions, and lead to an emissions-test failure.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.