P0669 — PCM/ECM/TCM Internal Temperature Sensor « A » Circuit High

The OBD-II trouble code P0669 indicates an issue with the internal temperature sensor circuit within the Powertrain Control Module (PCM), Engine Control Module (ECM), or Transmission Control Module (TCM). Specifically, it suggests that the sensor’s voltage reading is higher than expected, which could be caused by a malfunction or electrical problem. Note that labels and coding names can vary depending on the vehicle manufacturer.

Fast Facts

  • System affected: Powertrain Control System / Transmission System
  • Severity: Moderate, depending on the symptoms
  • Main symptoms: Check engine light, potential poor driveability
  • Driveability: Limited / No

Manufacturer variations for trouble code P0669

Manufacturers may assign different label IDs or code descriptions for the same issue, but P0669 primarily relates to the internal temperature sensor circuit in the PCM, ECM, or TCM. Variations include:

  • Ford: P0669
  • Honda: P0669
  • BMW: P0669
  • Volkswagen: P0669
  • Mercedes-Benz: P0669
  • And various other OEMs may use this same generic code with slight variations in the diagnostic trouble code description.

What does trouble code P0669 mean?

At its core, P0669 indicates that the vehicle’s PCM, ECM, or TCM has detected an abnormally high voltage signal in the internal temperature sensor circuit “A”. This sensor is responsible for monitoring critical internal temperatures within the component controlling engine or transmission functions. When the sensor’s readings suggest a high temperature or the circuit’s voltage exceeds the set threshold, the ECU triggers this code.

Generally, the ECU monitors the sensor’s voltage relative to temperature readings, expecting it to stay within a certain range. If the voltage reading is too high, it can trigger the fault code. This situation can occur during various engine or transmission operational states, especially during warm-up phases or under specific conditions where the circuit gets compromised.

Severity and risks of trouble code P0669

The severity of P0669 varies based on the vehicle’s behavior and other symptoms. While it might not bring the vehicle to a complete stop immediately, it indicates a potential problem with internal temperature readings that are vital for proper operation. If left unresolved, it can lead to erratic engine or transmission performance, increased wear, or even damage due to improper system management.

In most cases, driving the vehicle with this code is possible but not advisable without proper diagnostic attention. The vehicle might limp or operate with reduced efficiency. In some instances, if the sensor’s circuit is severely compromised, shutdowns or limp modes could activate to protect critical components.

Symptoms of trouble code P0669

Common symptoms associated with P0669 include:

  • Illuminated Check Engine Light or Service Vehicle Soon warning
  • Erratic transmission shifting or engine behavior
  • Reduced performance or power, especially under load or during warm-up
  • Unusual internal temperature gauge readings (if applicable)
  • Possible overheating warnings if the internal sensor influences cooling behavior

Most likely causes of trouble code P0669

Some causes are more prevalent than others when diagnosing P0669. Understanding the root problems can help streamline repairs and prevent unnecessary replacements.

  1. Faulty or damaged internal temperature sensor “A” within the PCM, ECM, or TCM assembly.
  2. Corrosion or poor electrical connection on the sensor’s wiring harness or connector.
  3. Damaged wiring harness or harness routing issues, causing high resistance or short circuits.
  4. Malfunction within the control module itself, possibly due to a firmware issue or internal failure.
  5. Environmental factors or water ingress affecting sensor or connector integrity.

How to diagnose trouble code P0669

Diagnosing P0669 involves a series of systematic checks to confirm the fault and identify its origin. These steps are broad and should respect manufacturer-specific procedures when available.

  1. Visually inspect the wiring harness and connector attached to the sensor for corrosion, damage, or disconnection.
  2. Check for other stored codes that could be related or help pinpoint the issue.
  3. Monitor live data using an OBD-II scanner to observe the internal temperature sensor readings under various operating conditions.
  4. Test the wiring continuity between the control module and the sensor to rule out open circuits or shorts.
  5. Perform voltage tests at the connector to verify the circuit voltage levels align with manufacturer specifications.
  6. If possible, replace the sensor temporarily with a known good unit to see if the fault clears or persists.

Possible repairs for trouble code P0669

Repairs depend on the identified cause. Here are typical solutions:

  • Replace the internal temperature sensor “A”: a common repair, best performed by a qualified technician.
  • Repair or replace damaged wiring harness or connector: often a basic repair, but may require professional expertise if extensive wiring issues are found.
  • Clean or secure electrical connections: a simple step that can restore proper circuit function.
  • Update or reflash the control module’s firmware: a professional repair in some cases, to fix internal faults.
  • Replace the entire control module: only if confirmed as faulty and other measures fail.

Vehicles commonly associated with trouble code P0669 in Europe

This code is not brand-specific but can

Retour en haut