Faulty EGR B valve or actuator with an internal short or high current draw; Wiring in the EGR B control circuit shorted to earth or chafed; Corroded, damaged or loose connector at the EGR valve or control unit; Carbon build-up in the EGR valve causing sticking and excessive load on the actuator; Water or coolant ingress into the actuator or its connector; Fault in the engine control unit output driver; Outdated control unit software where the manufacturer has issued a known correction.

P045C

EGR B Control Circuit Low.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
4: AreaAuxiliary emission controls
5C: FaultThe specific fault in that area

What it means

P045C is the generic code for a low signal in the control circuit of exhaust gas recirculation (EGR) system 'B'. The engine control unit monitors the voltage on the EGR B actuator control circuit and has seen it lower than expected for the commanded state, which usually points to a short to earth or a faulty actuator or driver. Which EGR the 'B' refers to (second bank or second valve) depends on the vehicle and engine.

Symptoms

Engine warning light on
Rough or unstable idle
Hesitation or poor response under acceleration
Occasional stalling at idle or when slowing down
Slightly reduced fuel economy
Engine may enter a limited performance mode

Possible causes

Faulty EGR B valve or actuator with an internal short or high current drawlikely
Wiring in the EGR B control circuit shorted to earth or chafedlikely
Corroded, damaged or loose connector at the EGR valve or control unitlikely
Carbon build-up in the EGR valve causing sticking and excessive load on the actuatorpossible
Water or coolant ingress into the actuator or its connectorpossible
Fault in the engine control unit output driverrare
Outdated control unit software where the manufacturer has issued a known correctionrare

How to diagnose

Read all stored and pending codes and note the freeze frame data, including engine temperature, load and speed when the code set
Check for related EGR codes or other circuit codes that suggest a shared wiring or power supply fault
Inspect the EGR B valve wiring and connector for chafing, melted insulation, corrosion, water and bent or pushed-back pins
Use a scan tool with live data or actuator tests to command the EGR B valve and compare commanded and actual position, if the vehicle supports it
Check the actuator supply voltage and earth at the connector, following the wiring diagram for that model
Measure the actuator coil or motor resistance and compare it with the manufacturer specification
With the harness disconnected at both ends, test the control wire for continuity and for a short to earth
Remove the valve if access allows and inspect it for heavy carbon, sticking or damage

How to fix

Repair or replace damaged wiring that is shorted to earth in the EGR B control circuit
Clean or replace corroded or damaged connector terminals and seal out any moisture
Replace the EGR B valve or actuator if it is shorted, seized or out of specification
Clean heavy carbon deposits from the EGR passages where the manufacturer allows, then refit the valve and test it
Check for a software update only if the manufacturer lists one for this fault, and have a suspect control unit tested before any replacement
Clear the code after repair and road test to confirm it does not return

Can I keep driving?

Medium severity

The car can usually be driven carefully for a short time, but the EGR system may not work correctly and the engine may run poorly or stall. Have it diagnosed soon, as a stuck or failed valve can increase emissions and may cause further drivability problems.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.