P0667 — PCM/ECM/TCM Internal Temperature Sensor « A »

Obd-II trouble code P0667 indicates a problem related to the internal temperature sensor within the Powertrain Control Module (PCM), Engine Control Module (ECM), or Transmission Control Module (TCM). This sensor monitors the temperature inside the control module to ensure proper operation and prevent overheating. Although the specific label may vary between vehicle manufacturers, this code generally points to an internal sensor fault.

Fast Facts

System affected: Powertrain Control Module (PCM)/Engine Control Module (ECM)/Transmission Control Module (TCM)
Severity: Moderate – may affect vehicle operation if unresolved
Main symptoms: Reduced engine performance, warning lights, potential limp mode
Driveability: Limited

Manufacturer variations for trouble code P0667

Depending on the vehicle manufacturer, the trouble code P0667 can be documented under different label variations. These variations are usually specific to OEM systems but refer to the same underlying issue related to the internal temperature sensor of the ECU/TCU.

For example, some manufacturers may use a code like U0105 or U0113 for communication errors, but P0667 is generally consistent across OEMs for this specific internal sensor issue.
Possible label variations include:
- Vehicle-specific DTCs: e.g., Ford’s U0003 for CAN communication issues, which may include internal sensor malfunctions.
- Generic OBD-II label: P0667 remains the default code across most manufacturers’ diagnostic protocols.

What does trouble code P0667 mean?

This diagnostic trouble code signifies that the vehicle’s Engine Control Unit (ECU), Transmission Control Module, or Powertrain Control Module has detected a problem with its internal temperature sensor “A”. This sensor is designed to measure the temperature inside the module itself, providing data vital for managing the module’s operation and preventing overheating.

In simple terms, P0667 means that the vehicle’s computer cannot get a reliable temperature reading from its own internal sensor. This can be caused by electronic faults, wiring issues, or sensor malfunctions. When this code appears, it usually happens in specific driving conditions, such as after a long period of vehicle use or during cold starts, where internal temperature management is critical.

The ECU uses the internal temperature data to ensure the module operates within safe thermal limits. If it detects inconsistencies, it triggers this trouble code to alert the driver that something is wrong internally, which could lead to potential overheating or malfunction if left unaddressed.

Severity and risks of trouble code P0667

P0667 is categorized as a moderate issue because it pertains to the internal health of the vehicle’s control modules. If ignored, it could potentially lead to more serious problems, such as overheating of the ECM/ECU, erroneous signals to other modules, or even complete failure of the component.

In terms of **risks**, an unresolved internal sensor fault might cause the vehicle to go into limp mode, reduce engine power, or trigger other diagnostic trouble codes related to system operation. It can also impact engine performance, fuel economy, and emissions control.

**Can the vehicle be driven?** — Limited. While it is often possible to drive the vehicle, it is generally advised to address the issue promptly to avoid further damage or unexpected breakdowns.

Symptoms of trouble code P0667

When P0667 is present, you may notice some signs indicating an internal issue within the control module. These symptoms are often subtle and can be mistaken for other electrical or sensor problems.

Warning lights: A check engine light or specific control module warning light appears on the dashboard.
Reduced engine performance: The vehicle behaves as if it’s in a limited power mode, especially during acceleration.
Erratic operation of electronic systems: Unusual behavior from sensors, actuators, or other electronic components.
Frequent stalling or rough idling: In cases where internal temperature affects the control module’s functioning.
Inconsistent or no response to diagnostic tools: Difficulties retrieving or reading live data from the ECU/ECM/TCM.

Most likely causes of trouble code P0667

This fault typically stems from internal component issues within the vehicle’s control modules or related wiring. Understanding the root causes helps in planning a proper repair strategy.

Faulty internal temperature sensor within the PCM/ECM/TCM: The sensor itself is defective or has failed due to age or thermal stress.
Electrical connection issues: Corrosion, loose wiring, or damaged connectors affecting sensor signals.
Internal damage to the control module: Overheating, moisture ingress, or manufacturing defects causing internal sensor or circuit failure.
Software glitches or outdated firmware: Rare but possible, causing improper sensor readings or diagnostic errors.
External factors: Excessive engine or ambient heat influencing internal temperature readings or sensor performance.

How to diagnose trouble code P0667

Diagnosing P0667 involves a systematic approach to confirm the internal sensor fault and eliminate other potential causes. Follow these basic steps as a guideline:

Visual Inspection: Examine the wiring harness and connectors related to the PCM/ECM/TCM for signs of damage, corrosion, or loose connections.
Check for related codes: Use diagnostic scan tools to see if other codes are present that might point to communication errors or related sensor issues.
Review live data: Connect a suitable scan tool and monitor the temperature readings from the module. Observe if the internal temperature sensor value is out of expected ranges, inconsistent, or missing.
Inspect the internal sensor circuit: Perform continuity tests on wiring and connectors to detect faults or open circuits.
Test the control module: If accessible, remove and test the control module’s internal components or consult OEM diagnostic procedures for specific sensor testing methods.

Possible repairs for trouble code P0667

Once the cause is identified, repairs generally focus on restoring proper sensor operation or addressing electrical faults. Some repairs can be classified as basic, while others require professional tools and expertise.

Replace the internal temperature sensor: If confirmed defective, this usually requires replacement of the control module or internal sensor component — a professional task in most cases.
Repair or replace damaged wiring or connectors: Cleaning corrosion, securing loose connections, or fitting new wiring harness segments — a task suitable for a skilled technician.
Update the control module’s firmware: If a software glitch is suspected, an OEM-specific update can resolve communication or sensor reading issues—performed by professionals.
Replace or repair the entire control module: In cases of internal damage or irreparable failure, replacing the ECM/ECU/TCM may be necessary, usually by a qualified workshop.

Vehicles commonly associated with trouble code P0667 in Europe

This fault is generally found across various vehicle brands, especially those with advanced control modules integrating internal temperature sensors. Specific data on affected models vary, but typical examples include:

Volkswagen Group: Volkswagen, Audi, SEAT, Škoda models with direct-injection engines and sophisticated ECUs.
Ford: Certain Ford models equipped with electronically controlled transmissions or engines.
BMW: Specific models with advanced engine control units.
Peugeot and Citroën: Vehicles with complex powertrain management systems.

Frequent mistakes with trouble code P0667

When diagnosing and repairing P0667, technicians often encounter similar pitfalls. Being aware of these can prevent unnecessary repairs and ensure accurate diagnosis.

Replacing parts without proper testing: Jumping to sensor replacement without confirming it is faulty can lead to wasted time and cost.
Ignoring related codes: Overlooking other stored codes may cause misdiagnosis of the root cause.
Misinterpreting live data readings: Misreading sensor signals or overlooking inconsistent data can lead to incorrect conclusions.
Neglecting wiring and connector issues: Focusing solely on the control module and ignoring electrical connections can leave the fault unresolved.

Quick FAQ — trouble code P0667

Can this code disappear on its own?

Typically, P0667 does not resolve spontaneously. It signals an underlying hardware or wiring issue that needs attention. Clearing the code might temporarily turn off the warning, but the problem will likely return unless addressed.

Can I keep driving?

While some vehicles may operate normally for a short period, continued driving with this fault can risk further damage to the control module or other engine components. It is advisable to have the vehicle inspected and repaired promptly.

Why does the code return after clearing it?

The code reappears because the underlying issue—such as a faulty sensor, damaged wiring, or internal control module failure—remains unresolved. Clearing the fault removes the symptom temporarily but does not fix the root cause, leading to recurrence.