AutoCodes – Generic – P0668

P0668 Code - Control Module Temperature Sensor Circuit Low Voltage

Quick Answer

The Transmission Control Module (TCM) temperature sensor is located inside of the control solenoid valve assembly which has no serviceable parts. Common causes include Faulty Control Solenoid Valve Assembly, Control Solenoid Valve Assembly harness is open or shorted, Control Solenoid Valve Assembly circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P0668 indicates Control Module Temperature Sensor Circuit Low Voltage.
Common causes: Common causes include Faulty Control Solenoid Valve Assembly, Control Solenoid Valve Assembly harness is open or shorted, Control Solenoid Valve Assembly circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 7,335

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Sep 23, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P0668 Description

The Transmission Control Module (TCM) temperature sensor is located inside of the control solenoid valve assembly which has no serviceable parts. The Transmission Control Module temperature sensor provides the temperature of the Transmission Control Module substrate. This temperature reading is used in various diagnostic routines in the Transmission Control Module software. This fault is handled inside the Transmission Control Module and no external circuits are involved. The Diagnostic Trouble Code (DTC) will be set when the TCM internal temperature is −249°C (−416°F) or less for 1 min.

OBDII Code P0668 - Control Module Temperature Sensor Circuit Low Voltage - AutoCodes.com — P0668 Code - Control Module Temperature Sensor Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P0668?

Faulty Control Solenoid Valve Assembly
Control Solenoid Valve Assembly harness is open or shorted
Control Solenoid Valve Assembly circuit poor electrical connection

How to Fix the DTC P0668?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0668 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P0668 code?

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Information for Specific Makes

P0668 BMW — DME Internal Fault Interior Temperature Sensor Signal
P0668 Buick — Control Module Temperature Sensor Circuit Low Voltage
P0668 Cadillac — Control Module Temperature Sensor Circuit Low Voltage
P0668 Chevrolet — Control Module Temperature Sensor Circuit Low Voltage
P0668 GMC — Control Module Temperature Sensor Circuit Low Voltage
P0668 Mazda — ECM/TCM Internal Temperature Sensor Circuit Low
P0668 MINI — DME Internal Fault Interior Temperature Sensor Signal

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.