P046F

What it means

P046F is the generic code for an intermittent or erratic signal from the exhaust gas recirculation (EGR) pressure sensor 'B' circuit. The engine control unit has seen the sensor signal jump, drop out or behave implausibly compared with engine conditions and other inputs. Which sensor is 'B', and how it is used, depends on the model and engine, so check the manufacturer's data.

Symptoms

• Engine management light on
• Rough or unstable idle
• Hesitation or poor response under acceleration
• Occasional surging or stalling
• Reduced power or limp mode on some vehicles
• Failed emissions test

Possible causes

• Damaged, chafed or corroded wiring to the EGR sensor B, giving intermittent open circuit or shortlikely
• Loose, corroded or contaminated connector terminals at the sensor or control unitlikely
• Faulty EGR sensor B (pressure, differential pressure or position type, depending on the model)likely
• Blocked or sooted sensor pipe, port or EGR passages causing erratic readingspossible
• Sticking or failing EGR valve affecting the sensor signalpossible
• Poor sensor supply voltage or ground, or a weak connection in the shared circuitpossible
• Fault within the engine control unitrare

How to diagnose

1. Read all stored and pending codes and record the freeze frame data to see engine load, speed and temperature when the fault set.
2. Look up the manufacturer's data to identify which sensor is 'B' on this engine and how it is wired.
3. Visually inspect the sensor, its pipes or hoses and the wiring harness for heat damage, chafing, splits, oil or water ingress.
4. Check the connector at the sensor and control unit for bent, loose, green or contaminated terminals, and check for secure locking.
5. With the engine running, view the live sensor signal and wiggle the harness and connector to see if the reading drops out or spikes.
6. Check the sensor supply voltage, reference and ground against the wiring diagram, and test the signal wire for continuity and shorts.
7. Inspect the sensor pipes, ports and EGR passages for carbon blockage, and check the EGR valve operates freely and responds to commands.
8. Compare the live reading with the manufacturer's expected values at key-on and at idle to judge whether the sensor itself is faulty.

How to fix

• Repair or replace damaged wiring, and secure the harness away from heat and sharp edges.
• Clean or replace corroded connector terminals, or replace the connector if it cannot be restored.
• Replace the EGR sensor B if it gives erratic readings with good wiring and supply.
• Clear blocked sensor pipes, ports or EGR passages of carbon, or replace pipes that are cracked or blocked.
• Replace or properly clean the EGR valve if it is sticking or not following commands, in line with the manufacturer's procedure.
• Clear the code after repair and road test to confirm it does not return.

Can I keep driving?

Nearby codes

• P046EGenericEGR Sensor B Circuit Range/Performance
• P0470GenericExhaust Pressure Sensor A Circuit