P045A

Gas Recirculation B Control Circuit

P045A is a generic OBD-II powertrain diagnostic trouble code: Gas Recirculation B Control Circuit. It is logged by the engine control unit when the egr monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P045A
Group
Powertrain
System
EGR
Severity
Warning (MIL on)
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What P045A means

P045A is a generic SAE powertrain code that sets when the Powertrain Control Module (PCM/ECM) detects an electrical fault in the control circuit for the secondary ("B") EGR solenoid or valve actuator. The "B" designator distinguishes this circuit from the primary EGR "A" circuit — on engines with dual-loop EGR systems (common in modern diesel and some gasoline direct-injection engines), a high-pressure loop and a low-pressure loop each have their own actuator; the "B" actuator typically governs the low-pressure or secondary loop. The PCM supplies ignition voltage to the solenoid and controls it by grounding the circuit; when the expected voltage or current conditions are not met during a commanded operation, the code is stored and the MIL illuminates.

The "Control Circuit/Open" suffix (vs. P045B Range/Performance, P045C Low, P045D High) means the PCM detected an open-circuit condition — no current flowing at all — rather than a signal that is simply out of range. This is almost always an electrical fault (broken wire, corroded connector, failed solenoid coil) rather than a mechanical EGR problem. Because the fault is circuit-based, the EGR "B" valve defaults to whatever position the mechanical spring holds it, which can be fully closed (no recirculation on that loop) or, if debris holds it open, cause rough combustion events. The code does not by itself indicate whether the valve is physically stuck.

P045A is considered a moderate-severity emission-system fault. It will not typically trigger limp mode or prevent the engine from starting, but it disables part of the EGR function, which increases NOx emissions, may affect fuel economy, and will cause a fail on any official emissions test. Prompt diagnosis is recommended to avoid catalyst stress from elevated exhaust temperatures and to stay compliant with emissions regulations.

Common causes

Most-frequently reported root causes when P045A is logged.

  • 1
    Open (broken or chafed) wire in the EGR B solenoid control circuit
  • 2
    Corroded, spread, or water-intruded pins at the EGR B solenoid connector
  • 3
    Failed EGR B solenoid coil (internal open circuit)
  • 4
    Loss of ignition supply voltage to the EGR B solenoid
  • 5
    Short to voltage on the control/ground side of the EGR B circuit
  • 6
    EGR B solenoid physically blocked by carbon deposits, preventing plunger movement
  • 7
    Faulty PCM driver for the EGR B output circuit (rare)

Symptoms drivers notice

MIL (Check Engine / Service Engine Soon light) illuminated
Rough idle or engine stumble, particularly if EGR B valve is stuck open
Hesitation or misfire under acceleration (excess exhaust gas in intake at wrong time)
Slight reduction in fuel economy due to disrupted EGR calibration
Increased NOx emissions; likely emissions test failure
No perceptible drivability change in some cases — electrical fault only, valve defaults closed

How to diagnose P045A

A typical diagnostic flow when this code is present.

  1. 1
    Scan for all stored and pending codes; note any related EGR, MAP, or MAF codes that may indicate secondary faults
  2. 2
    Inspect the EGR B solenoid connector and harness for corrosion, spread pins, chafing against hot or sharp surfaces, and water intrusion; repair as needed and retest
  3. 3
    With ignition on / engine off, use a scan tool to command the EGR B solenoid on — listen and feel for an audible click indicating solenoid activation
  4. 4
    If no click, backprobe the solenoid connector with a DVOM: verify ignition supply voltage is present on the power wire, then check the control wire for proper ground signal from the PCM
  5. 5
    Measure coil resistance across the solenoid terminals (typical range 10–30 Ω depending on make/model); infinite resistance confirms an open coil — replace the solenoid
  6. 6
    If supply voltage and ground are confirmed but solenoid does not activate, manually ground the control circuit to rule out PCM driver failure; if solenoid now clicks, suspect PCM output
  7. 7
    After any repair, clear codes, perform a drive cycle that activates the EGR system, and confirm no re-set of P045A or related codes

Vehicles where we've handled P045A

Platforms in our catalogue with confirmed P045A coverage.

AUDI A4 20D

Related powertrain codes

Frequently asked questions

Can I drive with a P045A code?

Yes, in most cases the vehicle remains drivable and will not enter limp mode. However, the EGR B circuit is disabled, which raises NOx output and may cause a rough idle if the valve is stuck open. You should diagnose and repair it promptly — especially before any emissions inspection.

Is P045A the same as P0404 or P0403?

No. P0403 and P0404 relate to the primary ("A") EGR circuit — P0403 is an electrical fault on the main EGR solenoid control circuit, and P0404 is a range/performance fault on the EGR position sensor. P045A is specifically for a second, independent EGR circuit ("B"), found on engines with dual-loop EGR. The diagnosis approach is similar but targets a different actuator and wiring branch.

What vehicles commonly trigger P045A?

Any OBD-II vehicle with a dual-loop EGR system can set P045A. It appears frequently on modern turbodiesel engines (Volkswagen, BMW, Ford, and GM diesel applications), certain Nissan/Infiniti V6 and V8 petrol engines, and high-efficiency direct-injection gasoline engines where a low-pressure EGR loop is used to reduce charge temperatures and NOx. Always confirm your specific vehicle has a B-circuit EGR before replacing parts.

Will replacing the EGR B solenoid always fix P045A?

Not always. P045A is a circuit code, meaning the fault could be in the wiring, the connector, the solenoid itself, or rarely the PCM. Replace the solenoid only after confirming the coil has an open circuit (infinite resistance) or the solenoid fails to click despite verified supply voltage and a good ground path. If wiring and connector checks pass and the solenoid measures within spec, suspect the PCM driver output.

Disabling P045A in software

RaceTune can permanently disable P045A — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

ECUs with a P045A disable in our catalogue

Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.

  • Bosch EDC17C74 verified 1 software version

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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