31-08-2022
13 min.
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P0667 PCM/ECM/TCM Internal Temperature Sensor Range/Performance

The P0667 trouble code is a generic OBD-II diagnostic trouble code related to the internal temperature sensor of the PCM, ECM, or TCM.

P0667 – PCM/ECM/TCM Internal Temperature Sensor Range/Performance

This code means that the vehicle's control module has detected that the signal from its internal temperature sensor is outside the expected range or does not behave as expected.

Unlike many sensor codes, P0667 does not necessarily refer to a separate temperature sensor mounted somewhere on the engine or transmission. In many vehicles, the temperature sensor is integrated into the electronic control module itself.

The exact meaning and diagnostic procedure can vary significantly between manufacturers.

What Does P0667 Mean?

P0667 can be understood as:

P = Powertrain
0 = Generic OBD-II code
6 = Computer output/control-related fault
6 = Internal temperature sensor
7 = Range/performance

In simple terms:

The control module believes its internal temperature sensor is reporting a temperature that is implausible, outside the expected range, or not changing correctly.

The affected module can be:

PCM — Powertrain Control Module
ECM — Engine Control Module
TCM — Transmission Control Module

Depending on the vehicle, one module may perform multiple functions.

What Is the Internal Temperature Sensor?

Electronic control modules contain processors, memory, voltage regulators and other electronic components.

These components generate heat while operating.

An internal temperature sensor allows the module to monitor its own temperature.

The module can use this information to:

Monitor electronic component temperature
Protect internal circuitry
Detect overheating
Adjust operation when necessary
Trigger protective strategies
Diagnose internal electrical problems

If the sensor signal becomes implausible, the module can store P0667.

What Does "Range/Performance" Mean?

The Range/Performance portion of P0667 is important.

It does not necessarily mean that the sensor circuit is completely open or shorted.

Instead, the control module has detected that the temperature signal is not behaving within the expected operating range.

For example, the module may detect a temperature value that is:

Too high
Too low
Implausible compared with operating conditions
Changing too quickly
Not changing when it should
Inconsistent with other internal temperature information

This is different from a straightforward electrical "high" or "low" circuit fault.

Symptoms of P0667

The symptoms depend heavily on the affected control module and vehicle.

Possible symptoms include:

Check Engine Light
Transmission warning light
Reduced engine performance
Transmission shifting problems
Limp mode
Delayed gear changes
Harsh shifting
Poor fuel economy
Engine starting problems
Intermittent warning lights
Multiple communication-related codes
Control module shutdown or reset
Intermittent electrical problems

Some vehicles may store P0667 with little or no noticeable drivability symptom.

Is P0667 Serious?

P0667 can be serious and should not be ignored.

The importance of the code depends on which module is affected and whether the module is actually overheating.

If the control module is experiencing excessive internal temperature, continued operation could potentially cause further electronic problems.

If P0667 is caused by an incorrect sensor reading rather than actual overheating, the vehicle may continue to operate normally for some time.

However, because the fault involves the control module itself, proper diagnosis is important.

Common Causes of P0667

Internal temperature sensor failure

The sensor integrated into the control module may have developed an internal fault.

Control module internal fault

An electronic component inside the PCM, ECM or TCM may be malfunctioning.

Control module overheating

Excessive temperature around the module can cause abnormal internal temperature readings.

Poor module ventilation or cooling

If the module is mounted in a location exposed to excessive heat or inadequate airflow, its temperature may become abnormal.

Power supply problem

Incorrect voltage supplied to the module can affect internal sensor readings.

Ground problem

A poor control-module ground can create abnormal electrical behavior.

Corroded connectors

Corrosion can increase electrical resistance and cause module-related faults.

Water intrusion

Moisture entering a control module or connector can damage electronic circuits.

Wiring problems

Depending on the vehicle, wiring or communication circuits associated with the module can contribute to the fault.

Software or calibration problem

In some vehicles, incorrect or outdated module software can cause abnormal temperature monitoring.

Actual excessive module temperature

The code can be triggered because the control module is genuinely getting too hot.

Can P0667 Be Caused by an Overheating ECU?

Yes.

This is one of the important possibilities.

If the ECM/PCM/TCM is located near a significant heat source, excessive temperature can affect its internal electronics.

Potential heat sources include:

Engine compartment heat
Exhaust components
Turbocharger
Transmission
Radiators
Cooling system components

If the module is actually overheating, simply replacing the module may not solve the problem unless the cause of the excessive heat is also addressed.

Can Low Battery Voltage Cause P0667?

Potentially, yes.

Control modules are sensitive to supply voltage.

A weak battery, poor battery connection, failing alternator or unstable power supply can cause unusual electronic behavior.

Check:

Battery voltage
Charging voltage
Battery terminals
Main grounds
Module power supply

before condemning the control module.

Can a Bad Alternator Cause P0667?

Yes, potentially.

An alternator that produces unstable voltage can interfere with control-module operation.

Voltage spikes or excessive electrical noise can also create unusual electronic faults.

If P0667 appears together with several unrelated electrical or communication codes, the charging system should be checked.

Can a Bad Ground Cause P0667?

Yes.

A poor ground connection can cause voltage differences within the control module.

Inspect:

Battery negative connection
Engine ground straps
Chassis grounds
ECM/PCM/TCM ground connections
Ground terminals for corrosion

A bad ground should be corrected before replacing an expensive control module.

Can Water Damage Cause P0667?

Yes.

Water intrusion can damage the internal electronics of a PCM, ECM or TCM.

Inspect for:

Corrosion
Moisture
Water marks
Green or oxidized terminals
Damaged connector seals

If the module has suffered water damage, the internal temperature sensor may be only one of several affected circuits.

Can P0667 Cause Limp Mode?

Yes, it can.

If the affected control module cannot reliably monitor its internal temperature, the vehicle may enter a protective operating strategy.

Depending on the vehicle, this may result in:

Reduced engine power
Limited transmission operation
Fixed gear selection
Delayed shifting
Reduced throttle response

Not every vehicle will enter limp mode.

Can P0667 Cause Transmission Problems?

Yes, if the TCM is involved.

If P0667 relates to the Transmission Control Module, the vehicle may experience:

Harsh shifting
Delayed shifts
Incorrect gear selection
Transmission limp mode
Limited available gears
Torque converter operation problems

If the TCM is integrated with another module, the symptoms may be different.

Can P0667 Cause Starting Problems?

Potentially.

If the affected ECM/PCM is malfunctioning or repeatedly resetting, the engine may have:

Extended cranking
Intermittent no-start
Engine stalling
Loss of communication with diagnostic equipment

However, P0667 by itself does not automatically mean that the vehicle will not start.

How to Diagnose P0667

Because the sensor may be integrated into the control module, diagnosis should focus on both the temperature reading and the condition of the module itself.

1. Scan all diagnostic trouble codes

Do not diagnose P0667 in isolation.

Look for:

Low-voltage codes
Communication codes
Module internal fault codes
Over-temperature codes
Sensor codes
CAN bus codes
Transmission codes

Additional codes can provide important clues.

2. Determine which module is reporting the code

Identify whether P0667 is associated with:

The scan tool and manufacturer-specific diagnostic information should identify the affected module.

3. Check live data

Look for the internal module temperature parameter if it is available.

Observe whether the temperature:

Appears reasonable
Is extremely high
Is extremely low
Remains fixed
Changes abruptly
Does not respond normally to ambient conditions

A temperature reading that is clearly implausible is a strong diagnostic clue.

4. Compare the temperature with actual conditions

For example, if the vehicle has been parked overnight and the scan tool reports an extremely high module temperature before the engine starts, the reading is suspicious.

Similarly, a temperature that remains unchanged while the module warms up may indicate a sensor or internal circuit problem.

5. Check module power supply

Measure the voltage supplied to the affected module.

Check both:

Power circuits
Ground circuits

Do not rely solely on a visual inspection.

6. Check the battery and charging system

Test:

Battery condition
Charging voltage
Alternator output
Voltage stability

Electrical instability can create confusing module faults.

7. Inspect connectors

Check the PCM/ECM/TCM connectors for:

Corrosion
Bent pins
Loose terminals
Water intrusion
Damaged seals
Poor terminal tension

8. Inspect the module environment

Determine whether the module is exposed to excessive heat.

Look for nearby:

Exhaust components
Turbocharger
Cooling system faults
Heat shields that are missing or damaged

9. Check module grounds

Verify all relevant ground circuits according to manufacturer specifications.

10. Check communication networks

If other communication codes are present, inspect the relevant CAN or communication circuits.

A communication problem can sometimes create multiple apparently unrelated module faults.

11. Check technical service information

Manufacturer-specific service bulletins and diagnostic procedures can be particularly important for P0667.

Some manufacturers may have known software updates or specific module tests.

12. Consider module replacement only after testing

If power, ground, wiring, cooling and communication circuits are correct and the internal temperature reading remains implausible, an internal module fault becomes more likely.

How to Test the Internal Temperature Sensor

This is different from testing a conventional external temperature sensor.

In many vehicles, the sensor is inside the PCM, ECM or TCM and cannot be accessed separately.

Therefore, you may not be able to simply disconnect the sensor and measure its resistance.

The preferred diagnostic method is usually to:

Connect a capable scan tool.
Access the module's live data.
Locate the internal temperature parameter.
Compare the reading with actual conditions.
Monitor the value as the module warms.
Check module power and ground.
Follow manufacturer-specific testing procedures.

If the manufacturer confirms that the internal sensor has failed, the entire control module may need to be repaired or replaced.

Can the Internal Temperature Sensor Be Replaced Separately?

Usually, no.

In many applications, the internal temperature sensor is integrated into the control module's circuit board.

This means replacing the sensor may require specialized electronic repair.

Depending on the vehicle, the practical repair may involve:

Professional module repair
Module replacement
Software programming
Immobilizer synchronization
Configuration
Coding

A replacement module may not simply work when plugged in.

Does P0667 Always Mean the ECU Is Bad?

No.

This is an important distinction.

Before condemning the ECU, ECM or TCM, verify:

Power supply
Ground
Battery voltage
Charging system
Connector condition
Water intrusion
Heat exposure
Wiring
Communication circuits
Software updates

An external electrical problem can sometimes cause a module to report an internal fault.

Can P0667 Be Caused by Software?

Yes, in some vehicles.

Control modules operate using software and calibration data.

A software issue may cause incorrect temperature monitoring or an incorrect diagnostic decision.

If the manufacturer has released a software update addressing P0667 or related module temperature monitoring, programming the module may resolve the issue.

Can P0667 Be Intermittent?

Yes.

An intermittent fault can occur because of:

Heat
Vibration
Loose connections
Voltage fluctuations
Internal electronic failure
Temperature-related component behavior

The vehicle may operate normally when cold and develop symptoms after the module becomes hot.

This pattern can be an important diagnostic clue.

Why Does P0667 Appear When the Engine Is Hot?

If the code appears only after extended driving, consider the possibility of heat-related module problems.

Monitor the internal module temperature before and after the fault occurs.

Also inspect whether the module is exposed to abnormal heat from nearby components.

Why Does P0667 Appear Immediately After Starting?

If the code appears immediately after a cold start, actual module overheating is less likely.

Possible causes include:

Incorrect internal temperature signal
Internal sensor failure
Module memory/software issue
Power supply problem
Ground problem
Connector problem

The live-data temperature reading can be particularly useful in this situation.

Can P0667 Be Cleared?

Yes.

The diagnostic code can generally be cleared using an appropriate OBD-II scan tool.

However, if the underlying problem remains, the code will likely return.

Clearing P0667 without diagnosing the cause does not repair the vehicle.

Can You Drive With P0667?

It depends on the symptoms.

If the vehicle operates normally and the code is intermittent, it may remain driveable temporarily.

However, if there is:

Limp mode
Transmission malfunction
Stalling
Loss of engine power
Multiple communication faults
Severe overheating
Intermittent no-start

the vehicle should be diagnosed promptly.

Common Diagnostic Mistakes With P0667

Immediately replacing the ECU

The module should not be condemned before checking power, ground, connectors and voltage stability.

Assuming the code refers to an external temperature sensor

P0667 often involves an internal module temperature sensor.

Ignoring battery voltage

Low or unstable voltage can create confusing electronic faults.

Ignoring module grounds

A poor ground can mimic internal module problems.

Ignoring heat exposure

A control module exposed to excessive heat may develop temperature-related faults.

Replacing the module without checking the cause

If excessive heat or water intrusion caused the original failure, the replacement module may eventually suffer the same problem.

Failing to program a replacement module

Many vehicles require programming, coding or configuration after ECM/PCM/TCM replacement.

What Is the Correct Repair for P0667?

The repair depends on the confirmed cause.

Possible repairs include:

Repairing a power supply problem
Repairing a poor ground
Cleaning or repairing module connectors
Repairing damaged wiring
Correcting water intrusion
Improving module heat protection
Replacing damaged heat shields
Repairing the charging system
Updating module software
Professionally repairing the control module
Replacing and programming the PCM/ECM/TCM

The internal temperature sensor itself may not be separately replaceable.

What Happens After Replacing the Control Module?

Depending on the vehicle, a replacement PCM, ECM or TCM may require:

Software programming
Vehicle configuration
Immobilizer/key synchronization
Security relearn
Transmission adaptation
Calibration updates

Therefore, module replacement should be performed according to the manufacturer's procedure.

How to Verify the Repair

After repairing the cause:

Clear the diagnostic codes.
Start the vehicle.
Monitor internal module temperature data.
Check charging voltage.
Monitor module communication.
Drive the vehicle under normal conditions.
Allow the module to reach normal operating temperature.
Re-scan for diagnostic codes.

P0667 should not return, and any related symptoms should be gone.

Frequently Asked Questions About P0667

What does P0667 mean?

P0667 means the PCM, ECM or TCM has detected a range/performance problem with its internal temperature sensor.

Is P0667 an engine temperature sensor code?

Not usually. It generally refers to a temperature sensor associated with the control module itself.

Does P0667 mean the ECU is bad?

Not necessarily. Power, ground, voltage, connectors, heat, wiring and software should be checked first.

Can P0667 cause limp mode?

Yes, depending on the vehicle and affected module.

Can P0667 cause transmission problems?

Yes, particularly if the TCM is affected.

Can P0667 cause hard starting?

Potentially, especially if the ECM/PCM is malfunctioning or resetting.

Can low battery voltage cause P0667?

It can contribute to abnormal control-module behavior.

Can a bad alternator cause P0667?

Yes, unstable charging voltage can contribute to module-related faults.

Can overheating cause P0667?

Yes. Excessive module temperature can cause or contribute to the fault.

Can water damage cause P0667?

Yes. Water intrusion can damage module electronics and connectors.

Can P0667 be intermittent?

Yes. Heat, vibration, voltage fluctuations and internal electronic problems can make the fault intermittent.

Can I drive with P0667?

Possibly for a short period if the vehicle operates normally, but the fault should be diagnosed, especially if warning lights, limp mode, transmission problems or stalling are present.

Can the internal temperature sensor be replaced?

In many vehicles it is integrated into the control module and is not designed to be replaced separately.

Do I need a new ECU for P0667?

Not automatically. Proper electrical and thermal diagnosis should be completed before replacing the module.

Final Thoughts on P0667

P0667 – PCM/ECM/TCM Internal Temperature Sensor Range/Performance indicates that a control module has detected an abnormal reading from its internal temperature monitoring circuit.

The main areas to investigate are:

Internal module temperature reading
PCM/ECM/TCM power supply
Ground connections
Battery and charging voltage
Module connectors
Water intrusion
Wiring
Excessive heat exposure
CAN communication
Software/calibration
Internal control-module failure

A logical diagnostic sequence is:

Scan All Modules → Identify the Affected Module → Check Additional Codes → Monitor Internal Temperature Data → Check Battery/Charging Voltage → Test Power and Grounds → Inspect Connectors → Check Heat and Water Exposure → Check Communication → Check Software Updates → Evaluate Internal Module Failure

The most important point is that P0667 does not automatically mean the ECU, ECM or TCM must be replaced. Because this code concerns the control module's internal temperature monitoring, accurate live-data analysis and electrical testing are essential before deciding that the module itself has failed.