P0669: Control Module Internal Temperature Sensor A Circuit High

Control modules measure their own circuit board temperature with an internal sensor to protect output stages (overtemperature is P0634) and, in GM transmission modules, as a substitute for fluid temperature. In GM's 6T70/6T75 and related automatics the sensor sits in the transmission module inside the valve body, with no external wiring – so the repair is practically always the module or valve body assembly. P0669 means the sensor signal is at the high voltage end (internal open or short to voltage): GM treats a converted value of 249 °C or more for 60 s as a fault, with the lamp after two trips and the power-up temperature as substitute. Unlike P0634, which reports a plausibly high real temperature (GM: 142 °C), P0669 reports a physically impossible value.

Symptoms

• Warning lamp
• Changed shift quality (substitute value)
• Scan tool shows an implausibly high module temperature

Most likely causes

• Module faulty internally (sensor open)
• Moisture or corrosion in the electronics
• Module supply or software

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the battery and grounds
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Clear the code and see if it returns
4. If it is a reference voltage code, disconnect sensors one at a time and see if the voltage recovers
5. Check whether a software update is available
6. Do not replace the control module without a full diagnosis

Good to know

• Repair difficulty: hard
• It can trigger limp mode.
• It affects emissions.

What each character of P0669 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 6: Control modules and outputs
• 69: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0669?

It depends on the symptoms. If the car is running normally you can go to a repair shop; if it goes into limp mode, drive as little as possible.

What causes code P0669?

The most common causes are: module faulty internally (sensor open); moisture or corrosion in the electronics; module supply or software.

Related codes

• P0668Control Module Internal Temperature Sensor A Circuit Low
• P0667Control Module Internal Temperature Sensor A Range/Performance
• P0666Control Module Internal Temperature Sensor A Circuit
• P0634Control Module Internal Temperature A Too High
• P0713Transmission Fluid Temperature Sensor A Circuit High

Sources

• law.cornell.edu: 13 CCR 1968.2
• gsi.ext.gm.com: 19OBDG03C Diagnostics
• saabwisonline.com: dtc p0667 p0668 or p0669

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.