01 Can Seafoam Fix Engine Problems? True Stories of Improved P… • 02 Tips for Extending the Life of Your Automatic Transmission … • 03 P0056, P0057, and P0058: HO2S Heater Control Circuit (Bank … • 04 Don’t Panic: Understanding Power Steering Fluid Leaks (Caus… • 05 B0012, B0013, B0014 - Right Front or Passenger Frontal Depl… • 06 That Faint Vibration In The Seat Could Be The First Sign Of… • 07 Understanding the Engine Block: A Comprehensive Guide • 08 People Admit They Ignored This Strange Noise Until Their En… • 09 Why Tire Pressure Light Sometimes Comes On Even When Tires … • 10 Exploring Variable Displacement Engines: Benefits and Drawb… •

DTC codes / P04xx · Auxiliary emission controls / P045C

P045CEGR B Control Circuit Low

P045C indicates that the powertrain control module has detected a low-voltage condition on the control circuit for the EGR B solenoid, which is the secondary exhaust gas recirculation valve on systems that use two EGR valves. The computer expects to see a voltage within a specific range when commanding the valve, and a reading below that threshold for a set time triggers this code.

SystemPowertrain
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaAuxiliary emission controls

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • A slight decrease in fuel economy because the EGR system is not functioning optimally
  • Intermittent rough idle or hesitation during light acceleration if the valve is stuck partially open
  • Increased nitrogen oxide emissions that may cause a failed emissions inspection
  • In rare cases, a surging or stumbling sensation when the engine is cold

Common causes, most likely first

  1. Open or shorted wire in the EGR B control circuit, often due to chafing or corrosion
  2. Failed EGR B solenoid, where the internal coil has an open circuit
  3. Corroded or loose electrical connector at the EGR B valve
  4. Faulty powertrain control module driver for the EGR B circuit, though this is less common
  5. Poor ground connection for the EGR B solenoid or its circuit
  6. Damage to the wiring harness from heat, rodents, or previous repairs

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related pending or history codes
  2. Visually inspect the EGR B solenoid connector and wiring for corrosion, damage, or looseness
  3. Measure the resistance of the EGR B solenoid with a multimeter and compare to the manufacturer's specification
  4. Check for battery voltage at the solenoid connector with the key on and the circuit commanded on
  5. Perform a voltage drop test on the ground side of the circuit to rule out a poor ground
  6. If the circuit and solenoid test good, suspect the powertrain control module and perform pinpoint tests before replacement
  7. Clear the code and test-drive the vehicle to confirm the repair and ensure the code does not return

What the EGR B low circuit really means

  • A low circuit code often results from a simple unplugged or loose connector that was missed during a previous repair, so always check the connector first.
  • The EGR B solenoid is frequently the secondary valve on systems with two EGR valves, and a failure of the primary valve can sometimes cause misleading symptoms.
  • A short to ground in the control wire can be intermittent and only set the code when the engine is hot or vibrating, so wiggle-test the harness while monitoring live data.
  • Replacing the EGR B solenoid without checking the circuit resistance can lead to a repeat failure if the root cause is a damaged wire or poor ground.
  • This code does not always mean the EGR valve itself is faulty; a low voltage signal can be caused by a failing driver in the powertrain control module, which requires thorough circuit testing.

Can I keep driving with P045C?

The vehicle is generally safe to drive with this code because it does not affect engine safety or cause a breakdown, but you should avoid long-term driving because it can increase emissions and slightly reduce fuel economy. Have the fault diagnosed soon to prevent potential secondary issues and to ensure the vehicle passes emissions testing.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage