U066D: Lost Communication With Charge Air Cooler Temperature Sensor Bank 1

What it means

The vehicle bus reports loss of communication with smart charge air cooler (intercooler) temperature sensor on bank 1. Charge-air density correction switches to a substitute value.

At a glance

• Usually lights the warning light of the system that lost communication
• Affects emissions; the car can fail an emissions test

How it works

The charge air cooler, also called the intercooler, cools compressed intake air; the bank 1 temperature sensor sends its readings over the vehicle network. The control module sets U066D when communication with that specific sensor is lost, so charge-air density correction must use a substitute value.

Common causes

Most likely first.

1. Bus wiring open or shorted
2. Module without power or ground
3. Module failed

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Scan all modules for communication codes and review freeze-frame data to see whether the fault began with other network dropouts.
2. Check scan-tool data for the bank 1 charge air cooler temperature sensor and compare its status with the bank 2 sensor, if fitted.
3. Inspect the bank 1 sensor connector and wiring at the charge air cooler for moisture, corrosion, looseness, or physical damage.
4. Check the sensor's power and ground, then test its network wires for opens, shorts, or poor connections using the manufacturer's wiring information.
5. If the circuit and supplies are sound, test communication at the bank 1 sensor and determine whether its module has failed.

Common fixes

• Reconnect or clean the bank 1 charge air cooler temperature sensor connector and repair damaged wiring.
• Restore a missing or poor power or ground connection at the bank 1 sensor.
• Repair an open or short in the network wiring to the bank 1 sensor.
• Replace the bank 1 sensor if its power, ground, and network connections are good but it remains offline.

Can I keep driving?

If the engine runs normally, a short gentle trip may be possible, but avoid sustained high boost or heavy loads because charge-air temperature compensation is using a substitute value. Stop if power loss, overheating, or other serious warnings appear.