P045C

Code

Generic P — Powertrain

EGR B Control Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 19 EN: 42 RU: 24

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Page language: EN

Causes

Open, short to ground, or short to voltage in the EGR B control wiring or connectors
Faulty EGR B valve, solenoid, or actuator (internal short or low coil resistance)
Poor or corroded connector pin contact at valve or PCM
Blown fuse or poor 12 V supply to the EGR circuit
Faulty PCM output driver
Intermittent connection or mechanical damage to wiring harness

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Reduced engine performance or hesitation under load
Rough idle or stumbling if EGR operation is affected
Failed emissions test (increased NOx)
Possible stored or pending related EGR flow/position codes

What to check

Read freeze frame and live data for EGR command and feedback values
Scan for additional related codes (EGR flow, position, supply faults)
Visually inspect EGR B connector and wiring for damage, corrosion, pin push-out or oil contamination
Verify relevant fuses and 12 V supply to the EGR circuit
Backprobe EGR B connector and measure voltage while commanding EGR ON/OFF
Measure coil/actuator resistance at the harness and compare to spec

Signal parameters

Control signal type: typically PCM-driven switched circuit (low-side) or PWM; duty 0–100% when commanded
Expected commanded voltage: low ≈ 0 V when PCM switches to ground, high ≈ battery voltage (approx. 12 V) when not switched (or vice versa depending on vehicle design)
Typical PWM frequency: manufacturer-dependent (often 5–50 Hz for some EGR solenoids); consult vehicle data for exact frequency
Actuator coil resistance: commonly in the tens to low hundreds of ohms (varies by actuator); compare to vehicle spec
If circuit is 'low' the measured control voltage will be near 0 V when it should be high or the PCM output reads a low-voltage fault

Diagnostic algorithm

Retrieve all codes and freeze frame data. Note engine conditions when fault set (temp, RPM, load).
Inspect the EGR B connector and harness for corrosion, damage, pin deformation or oil intrusion. Repair any visible issues.
Verify power and ground sources: check related fuses, battery voltage at the EGR supply and secure ground connections.
With key on (engine off), backprobe the control and supply pins at the EGR B connector. Record voltages at rest.
Command the EGR B ON using a scan tool while monitoring the control pin. Observe voltage or PWM duty change; if voltage remains low, suspect wiring/actuator/PCM.
Measure actuator coil resistance (engine off, connector disconnected). If resistance is out of specification (open or short), replace actuator.
Check continuity between the EGR B connector and the PCM pin for opens/shorts to ground or battery. Repair any wiring faults.
If wiring and actuator check OK, perform a bench or fused jumper test to actuate the valve briefly (apply appropriate voltage per vehicle spec) to confirm mechanical operation. Use caution and a fuse when applying power.
If harness and actuator are good but circuit still indicates low, suspect PCM driver fault. Verify with OEM wiring diagrams and consider PCM bench testing or replacement per manufacturer procedures.
After repair, clear codes and road test under conditions that previously set the code. Confirm no return of P045C and related EGR complaints.

Likely causes

Corroded/loose connector at the EGR B actuator or harness chafing causing a short to ground
Failed EGR B solenoid/actuator with internal electrical fault
Open or shorted control wire between PCM and EGR B
Bad ground or blown fuse affecting the circuit

Fault status

⚠️ Status

EGR B control circuit low voltage detected — PCM commanded EGR B but measured control circuit voltage is below expected threshold (possible short to ground, open, faulty actuator, or PCM output fault).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2 hours