Damaged, corroded, or disconnected wiring or connector at the charge air cooler temperature sensor.; Failed charge air cooler temperature sensor itself, producing no valid data on the communication bus.; Open or shorted communication bus circuit between the sensor and the module that reports its data.; Faulty control module that is supposed to relay or receive the sensor message, such as a failed powertrain control module.; Water intrusion or heat damage in the sensor harness causing intermittent communication loss.; Low battery voltage or poor grounds that disrupt module communication across the network.

DTC codes / U06xx · Network communication / U066D

U066DLost Communication With Charge Air Cooler Temperature Sensor Bank 1

U066D is a network communication code indicating that a control module on the vehicle's data bus has stopped receiving valid messages from the charge air cooler temperature sensor on bank 1. The computer detects this when the sensor's periodic status messages fail to arrive within the expected time window, which usually points to a wiring fault, a failed sensor, or a module communication issue rather than a direct temperature reading problem.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaNetwork communication

Symptoms you may notice

Illumination of the check engine light or service vehicle soon message with no other obvious drivability change.
Reduced engine power or limp mode if the powertrain control module substitutes a default charge air temperature value.
Poor fuel economy or altered turbocharger boost behavior because the computer lacks accurate intake air temperature data.
Intermittent rough running or hesitation under acceleration when the sensor signal drops out momentarily.
Often no symptoms besides the warning light, especially if the fault is stored but not currently active.

Common causes, most likely first

Damaged, corroded, or disconnected wiring or connector at the charge air cooler temperature sensor.
Failed charge air cooler temperature sensor itself, producing no valid data on the communication bus.
Open or shorted communication bus circuit between the sensor and the module that reports its data.
Faulty control module that is supposed to relay or receive the sensor message, such as a failed powertrain control module.
Water intrusion or heat damage in the sensor harness causing intermittent communication loss.
Low battery voltage or poor grounds that disrupt module communication across the network.

How to diagnose and fix it

Inspect the charge air cooler temperature sensor connector and harness for corrosion, chafing, or loose pins, and repair as needed.
Measure reference voltage and ground at the sensor connector to confirm the circuit is intact before condemning the sensor.
Check the communication bus resistance and continuity between the sensor circuit and the reporting module to rule out an open or short.
Replace the charge air cooler temperature sensor if wiring checks pass but no valid data is seen on a scan tool.
Verify battery voltage and ground connections at the control modules involved, as low voltage can mimic communication faults.
Clear the code and perform a road test to confirm the sensor data returns and the code does not reset.
If the fault persists, follow the manufacturer's diagnostic flow for the specific module network to isolate a failed control module.

What most technicians miss on U066D

This code often sets because of a poor connection at the sensor plug rather than a failed sensor, so wiggle-testing the harness while watching live data can reveal the real fault.
A charge air cooler temperature sensor that reads plausibly but intermittently drops off the bus will set U066D without ever storing a temperature rationality code.
Low battery voltage or a weak ground can cause multiple modules to lose communication, so check for other U-codes before replacing any single component.
The sensor may share a communication bus with other sensors, and a fault elsewhere on that bus can prevent its message from arriving and trigger this code.
Replacing the sensor without checking the reporting module's software updates or known communication issues can lead to a repeat repair.

Can I keep driving with U066D?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration or towing because the computer may be using a default charge air temperature and could reduce power unexpectedly. If the engine enters limp mode or runs poorly, stop driving and have the fault diagnosed promptly.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.