P306d Peugeot ⚡ Fully Tested
Before replacing any parts, understand that this is an electrical circuit code, not a mechanical failure. Here are the probable causes, ranked from most to least likely:
The P306D fault code is a specific diagnostic trouble code (DTC) found in Peugeot and Citroën models equipped with DV6 diesel engines (most commonly the 1.6 HDi / e-HDi). The code technically stands for "Information on the current consumed by the injector: Injector 1/4."
In plain English, this means the engine computer (ECU) has detected an electrical anomaly with the Number 1 Cylinder Injector. It is not a sensor failure; it is a failure of the hardware itself or the wiring leading to it.
P306D = "Cylinder 3 – Torque contribution less than expected threshold."
This means cylinder 3 is firing, but very weakly. The engine is running, but the ECU sees that cylinder isn’t pulling its weight in terms of power output. It’s not a simple misfire (P0303), but a performance/efficiency misfire.
Difficulty: Moderate to Hard (V6 engines have limited access).
Cost: $20–$60 (OEM plug) + labor.
This is considered a known weakness in the DV6 engine family (used in Peugeot 207, 208, 308, 2008, and Partner models).
Verdict: P306D is a "hard fault." It will not go away on its own. Continued driving with a misfiring injector can cause unburnt fuel to enter the exhaust system, eventually destroying your DPF (Diesel Particulate Filter)—a repair that costs significantly more than a single injector.
Recommendation: Address this immediately. Replace the injector and inspect the wiring loom for oil ingress while the mechanic is in there.
The Peugeot fault code (often specifically ) relates to coherence issue
between the electronic throttle housing position and the inlet air pressure
. Essentially, the car's Engine Control Unit (ECU) detects that the physical position of the throttle valve does not match the air pressure readings it expects. Common Symptoms Engine Management Light (EML):
The orange engine warning light illuminates on the dashboard. Limp Mode:
The vehicle may enter a restricted performance mode to protect the engine, often limiting RPM or disabling the turbocharger. System Failures:
Owners frequently report secondary faults like "Active Cruise Control Fault" or speed limiter failure occurring just before the engine light. Erratic Idle/Stalling:
Issues often manifest at low speeds (e.g., in city traffic) or during idle. Potential Causes Faulty Throttle Body (Air Mixer):
The sensor within the electronic throttle housing may be failing or contaminated. Inlet Air Pressure (MAP) Sensor:
A faulty or dirty Manifold Absolute Pressure (MAP) sensor can provide incorrect data to the ECU. EVAP System Issues:
A broken purge valve or a failing carbon (EVAP) canister can cause air pressure discrepancies, specifically at low speeds or idle. Wiring/Connectors:
Corrosion or damage to the wiring harness and plugs can cause intermittent signal loss. Peugeot 306 Owners Club Recommended Troubleshooting Scan the ECU: OBD2 diagnostic scanner like those used by Meta Mechanics p306d peugeot
to confirm if the code is persistent and check for accompanying "ghost" codes. Inspect Sensors:
Check the throttle body and MAP sensor for carbon buildup or electrical damage. Check the EVAP Solenoid:
On models like the 508 or 3008, the solenoid valve (often part number V759557380
) located under the air filter box is a known failure point that triggers this specific code. Clean Connections:
Inspect the pins on the throttle position sensor (TPS) for water ingress or corrosion, which is a common issue in older models like the 306. Peugeot 306 Owners Club
For a permanent fix, it is best to visit a qualified specialist who can perform live data logging to see if the throttle position and air pressure are truly out of sync during driving. Meta Mechanics local Peugeot specialist garages in your area to help diagnose this specific fault? P306D-22 coherence problem - French Car Forum
The Peugeot fault code (specifically signifies a coherence problem
between the position of the motorized throttle housing (air mixer) and the inlet air pressure
. Essentially, the car's Engine Control Unit (ECU) is detecting a mismatch: the air pressure at the intake doesn't align with where the throttle valve is positioned. Symptoms & Impact When this code is triggered, you will likely experience: Engine Management Light (EML):
The orange engine warning light will appear on the dashboard. Limp Mode:
The vehicle may restrict engine RPM and power to protect the engine. Speed Limiter/Cruise Control Failure:
These systems are often automatically disabled when an engine management fault is detected. Erratic Performance:
You might notice a sluggish feel or decreased fuel efficiency. JustAnswer Common Causes Faulty Throttle Body/Air Mixer:
The motorized unit may be sticking, contaminated, or its internal position sensor may be failing. Inlet Air Pressure (MAP) Sensor:
A faulty or dirty sensor might be sending incorrect pressure readings to the ECU. EVAP System Issues: Some technicians have linked this code to a faulty EVAP purge valve
or a saturated charcoal canister, often located near the air filter box. Wiring and Connectors:
Corrosion or loose pins in the throttle sensor harness can cause intermittent signal loss. Peugeot 306 Owners Club Recommended Diagnostic Steps Visual Inspection:
Check the throttle body for carbon buildup or blockages and inspect the wiring harness for signs of heat damage or corrosion. Professional Scan: Use a Peugeot-specific diagnostic tool like
to read live data. This helps determine if the "value is higher than setting," which points specifically to the air intake coherence. Check the EVAP Valve: Before replacing any parts, understand that this is
On models like the 308 or 508, testing the solenoid valve located beneath the air filter box is a common fix for persistent P306D issues. P306D-22 coherence problem - French Car Forum
Understanding the Peugeot P306D Error Code: Causes, Symptoms, and Fixes
If you own a modern Peugeot—particularly models like the DS7 Crossback, 508, or others equipped with 1.6 PureTech engines—and are faced with a "Check Engine" light, you might encounter the elusive P306D fault code. Unlike standard P0xxx codes, this specific PSA (Peugeot/Citroën) group code points towards a complex interaction between engine management components.
This article explores what the P306D code means, why it happens, and how to fix it based on technical diagnostics. What is the P306D Code in a Peugeot?
The P306D-22 code on a Peugeot, often accompanied by a "22" suffix (P306D-22), is typically defined as:"Coherence between the position of the motorized throttle-housing (air mixer) and the inlet air pressure: Value higher than setting".
In simpler terms, the ECU (Engine Control Unit) expects a certain amount of air pressure (read by the MAP sensor) to correspond with the position of the electric throttle body/air mixer. When these two readings do not match, the system throws this coherence error.
Note on Confusion: While some generic scanners might suggest this is related to a cylinder misfire, on newer Peugeot PSA vehicles, it is strongly related to air intake/throttle issues. Common Symptoms of P306D
When this code is stored, your vehicle may exhibit several concerning behaviors:
Check Engine Light (EML) and "Engine Fault: Repair Needed" message on the dashboard.
Limp Mode (Reduced Power): The engine restricts power, limiting speed to around 30-40 mph.
Failed Speed Limiter/Cruise Control: These functions may stop working. Rough Idle or Stalling: Particularly after cold starts.
Cooling Fans Running Constantly: The radiator fans may run at high speed even when the engine is cold or just after it is turned off. Erratic Gear Changes (if automatic). Primary Causes of P306D
Based on mechanic diagnostics and forum discussions, the P306D code is commonly caused by:
Faulty Purge Valve/Evap Canister Solenoid: A frequent cause is the purge valve, located near the intake system, failing to regulate pressure properly, especially at low speeds.
Electric Throttle Body (Air Mixer) Malfunction: The throttle actuator itself may be faulty or contaminated, leading to inaccurate positioning.
Inlet Air Pressure Sensor (MAP Sensor): If the sensor provides incorrect data, the coherence check will fail.
Wiring Harness Issues: Corrosion or damage to the connectors feeding the throttle body or pressure sensors.
Carbon Buildup: On direct-injection engines, carbon buildup around the throttle plate can cause improper airflow readings. How to Diagnose and Fix P306D
Solving the P306D code requires a methodical approach, ideally using a specialized PSA diagnostic tool like Diagbox. 1. Initial Inspection (Easy) P306D-22 coherence problem - French Car Forum If you own a modern Peugeot (such as
The P306D fault code on Peugeot vehicles (often appearing as P306D-22) typically indicates a coherence or consistency issue between the electronic throttle housing position and the inlet air pressure. This specific error is common in modern Peugeot and DS models, such as the 508, 308, and DS7 Crossback. Common Symptoms
Active Cruise Control Fault: Often the first warning to appear on the dashboard.
Check Engine Light (EML): Typically follows the cruise control error, especially during low-speed "city" driving.
Limp Mode: The vehicle may enter a restricted power state to prevent engine damage.
Speed Limiter Failure: Disabling of driver assistance systems. Potential Causes & Diagnostic Steps
The error signals that the engine computer is seeing a mismatch between how much air it thinks should be entering (based on throttle position) and how much is actually entering (based on pressure sensors).
Purge Valve / EVAP System: Many owners have successfully resolved P306D by replacing the EVAP purge solenoid valve or the EVAP canister. In models like the 2019 508, this valve is often located beneath the air filter box near the rear of the engine.
Electronic Throttle Body: A faulty or contaminated throttle position sensor can cause incorrect readings, particularly at low speeds.
Inlet Air Pressure Sensor: A failing sensor or a leak in the intake tract can cause "incoherence" in the pressure readings.
Wiring/Connectors: Inspect for corrosion or damage at the throttle body and pressure sensor plugs. Troubleshooting Recommendations
Read Diagnostic Trouble Codes (DTCs): Use a tool like Diagbox to confirm the sub-code (e.g., P306D-22) for more specific guidance.
Inspect the Purge Valve: Given community feedback, check the solenoid valve for proper operation, as it is a frequent culprit for air coherence faults.
Clean the Throttle Body: Ensure there is no carbon buildup preventing the throttle plate from moving smoothly. P306D-22 coherence problem - French Car Forum
If you own a modern Peugeot (such as the 208, 308, 508, 3008, or Boxer) and your diagnostic scanner has flashed the code P306D, you are likely looking at your dashboard’s engine management light (EML) with a mixture of confusion and concern. Unlike common codes like P0171 (system too lean) or P0420 (catalyst efficiency), P306D is a manufacturer-specific code. This means its definition is not standardized across all car brands—it is unique to the PSA (Peugeot-Citroën) group and its partner, Ford (for certain diesel engines).
In this article, we will dissect everything you need to know about the P306D Peugeot fault code: what it means, what causes it, how to diagnose it correctly, and—most importantly—how to fix it without wasting time or money on unnecessary parts.
The "D" in P306D stands for Diesel, but not the common-rail, computer-controlled diesels we know today. This is the legendary XUD9 engine—a 1.9-litre, 8-valve, indirect injection diesel.
The Good (The Immortal Part):
The Bad (The Time Bomb Part):