🔍 Meaning
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Generic OBD-II code related to the “C” electrical circuit of the EGR (Exhaust Gas Recirculation) system.
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The PCM/ECM detects an abnormal electrical signal (voltage too low, too high, or absent).
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Note: The “C” designation varies by manufacturer (refer to the specific manual).
⚙️ EGR Function
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Purpose: To inject exhaust gases into the intake manifold to:
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Reduce combustion temperatures below 1300°C (prevent NOx formation, a pollutant responsible for smog).
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Activates only at high RPM (> 2000 RPM) to avoid power loss or stalling.
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⚠️ Symptoms
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Check Engine Light (MIL) illuminated ⚠️.
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Frequent associated codes:
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P044C(low voltage) /P044D(high voltage) /P044E(intermittent signal).
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Mechanical issues:
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Stalling or rough idle (if valve stuck open).
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Knocking during acceleration (if valve stuck closed).
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Special case: No observable symptoms.
🔧 Possible Causes
| Category | Details |
|---|---|
| Electrical Issues | – Faulty EGR “C” sensor. – Cut/shorted wires. – Oxidized connectors or damaged pins. |
| EGR Malfunctions | – Clogged EGR valve (stuck closed by carbon). – Vacuum circuit leak. – Faulty control solenoid. |
| Specific Components | – Defective EGR position sensor. – Faulty DPFE (Differential Pressure Feedback) sensor (especially on Ford). |
🛠️ Repair Procedures
1. Quick checks (no specialized tools):
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Inspect EGR connectors:
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Clean corrosion, straighten bent pins.
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Check vacuum hoses:
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Replace if cracked or detached (especially between solenoid and EGR valve).
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Clean EGR valve:
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Remove → Clear carbon obstructing passages.
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2. Specific case (Ford):
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Locate the DPFE sensor (rear of intake manifold).
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Clean the 2 rubber hoses connected to the exhaust with a fine tool.
3. Advanced diagnostics (requires equipment):
| Step | Action |
|---|---|
| Electrical circuit test | Measure wiring harness voltage/continuity (refer to manufacturer diagram). |
| “C” sensor check | Verify its resistance (manual specifications). |
| PCM simulation | Use a scanner to force EGR open/close. |
⚠️ Warning:
Never probe a circuit without an accurate diagram (risk of PCM damage).
Avoid disconnecting random connectors (may erase PCM programming).
💡 Final Recommendations
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Temporary solution: EGR cleaning resolves 50% of carbon-related cases.
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Common mistakes:
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Neglecting DPFE hoses (Ford).
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Forgetting to check vacuum circuit integrity.
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If unsuccessful:
🔧 Refer to a professional equipped with OEM diagnostic tools (e.g., Ford IDS, GM Tech2).
ℹ️ Note: This code is often accompanied by P044A (general “C” circuit fault) – their diagnosis is similar.