Guide To P0666 OBD Error Code Solutions

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The trouble code P0666 can be defined as PCM/ECM/TCM Internal Temperature Sensor Circuit. This diagnostic fault code is a generic powertrain code, which means that it would apply to the OBD-II equipped vehicles. The specific repair steps can vary as it depends upon the vehicle make and model.

If the powertrain control module, engine control module, or transmission control module would detect some fault in the internal temperature sensor circuit, then the P0666 trouble code would start flashing up.

What causes this problem with the PCM/ECM/TCM Internal Temperature Sensor Circuit?

• The wiring might be defective
• Loose or faulty control module ground strap
• Some faults in the PCM, ECM or TCM
• Faults in the transmission cooler
• The connector might be damaged or corroded
• Kinked or damaged transmission fluid lines
• Obstruction in the airflow of the radiator or transmission cooler

1. Powertrain Control Module - A faulty Powertrain Control Module can be troublesome. You can always rely on us as we have best auto parts for our customers.
2. Electronic Control Unit - If everything is alright with PCM, then there is surely some defect in Electronic Control Unit. Get it replaced before the situation gets worse.
3. Engine Control Module - P0666 code can display due to some defects in the Engine Control Module. So, it is very important to replace the Engine Control Module with us at equitable prices.
4. Automatic Transmission Sensor - Do you remember when was the last time you got your car Automatic Transmission Sensor checked up? A defective Automatic Transmission Sensor can cause a lot of issues like displaying P0666 code.
5. Body Control Module - Poor Body Control Module can cause a lot of difficulties, so why not get it replaced at time?
6. ABS System Parts - There can be some issues with the ABS System Parts due to which you may see P0666 code appearing over and over again. Visit us to buy best quality ABS System Parts online.
7. Auto Transmission Shift Solenoid - Are you facing some faults in your Auto Transmission Shift Solenoid? Don’t worry and get them replaced or else P0666 code can turn up.

It is vital to know the symptoms of an issue as only then you would be able to solve the problem. So that’s why we have listed out some major symptoms of OBD Code P0666 here:

Common Symptoms

• There can be some issues in starting the car engine
• The car might not start at all
• Engine stall problems
• Transmission warning lamp can start appearing
• Illumination of the malfunction indicator lamp

Looking out for some ways with the help of which you can correct this fault code? Then you have arrived at the correct place. We are here to help you out, so you must check out the steps mentioned below as follows:

• If there is a failure in the module, then you must replace it
• You must correct the multiple failed modules
• Make sure to replace the defective powertrain control module

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Here are some steps which you should follow in order to diagnose this fault code:

• Start your diagnosis by testing all power and ground circuits for the affected module. Compare your findings with manufacturer’s specifications and make necessary repairs
• Be sure to clear all trouble codes and retest the system in order to ensure that the condition is rectified. If all power and ground circuits align with the manufacturer’s specifications, suspect a faulty control module
• Control module replacement will also require reprogramming it to match the vehicle. CAN stands for “controller area network.”
• The CAN represents a communication bus that allows multiple microcontrollers to communicate with one another without the need for a host computer
• The CAN bus network is actually a complex conglomeration of wiring harnesses and connectors used as a pipeline of information shared between two or more automotive control modules
• These controllers control virtually every electrical function of the vehicle, with the PCM being the primary controller
• The cruise control module uses the data for speed control purposes, the traction control system uses the data to regulate vehicle traction control strategy, and the anti-lock brake controller compares vehicle speed from the PCM with data inputs from individual wheel speed sensors to operate the anti-lock braking system
• Several tools will be instrumental in attempting to successfully diagnose this code
• A suitable OBD-II scanner (or code reader) and a digital volt/ohmmeter will be most helpful in trying to perform a successful diagnosis
• Then start with a visual inspection of all wiring and connectors
• Repair or replace damaged, disconnected, shorted, or corroded wiring, connectors, and components as necessary
• Always retest the system after repairs are completed to ensure success. If all system wiring, connectors, and components (Including fuses) appear to be in normal working order, connect the scanner (or code reader) to the diagnostic connector and record all stored codes and freeze frame data
• Continue by clearing the code and operating the vehicle to see if it returns. This will help to determine whether or not the malfunction is intermittent
• After the codes are cleared, test drive the vehicle to see if the code returns. If the code fails to immediately return, you may have an intermittent condition
• Intermittent conditions can prove to be quite a challenge to diagnose and in extreme cases may have to be allowed to worsen before a correct diagnosis can even be attempted
• Disconnecting and testing every single pin of the CAN bus could prove to be extremely time and cost prohibitive
• Additionally, some type of memory saving device must be installed, lest the PCM and other controllers lose their memory and require reprogramming
• Control module ground circuits should be tested for continuity with battery ground
• These types of codes are frequently caused by defective or disconnected system grounds. An auxiliary ground cable can be helpful in diagnosing system ground discrepancies
• Compare your findings with the manufacturer’s referenced values and repair open or shorted circuits as required
• It is often much more frugal to replace defective wiring rather than attempting to remove it from the complex web of wiring harnesses

Common Mistakes When Diagnosing the P0666 Code

• A lot of times multiple control modules can fail along with the shorted or defective ground wiring, so you must repair them