U0675: Lost Communication With Turbocharger/Supercharger Speed Sensor A

What it means

The vehicle bus reports loss of communication with smart turbocharger speed sensor A. Overspeed protection switches to model-based estimation; boost may be limited.

At a glance

• Usually lights the warning light of the system that lost communication
• Affects emissions; the car can fail an emissions test
• The engine or gearbox may go into limp mode

How it works

A smart turbocharger or supercharger speed sensor A measures how quickly the boost-producing unit spins and sends its readings over the vehicle network. The control module sets U0675 when it stops receiving messages from that sensor; it may estimate speed instead and limit boost to reduce overspeed risk.

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 save freeze-frame data before clearing anything, since related faults can show whether the loss is isolated to sensor A or part of a wider network problem.
2. Check whether the turbocharger or supercharger speed reading is missing or implausible in live data, and note any boost limitation or overspeed-related warnings.
3. Inspect the sensor A connector and its network wiring for looseness, corrosion, chafing, heat damage, or a short to another wire.
4. Check the sensor's power and ground circuits against the manufacturer's specification, because a failed supply can make a functioning sensor disappear from the bus.
5. Test the network wiring to sensor A for opens or shorts using the manufacturer's diagnostic procedure.
6. If wiring, power, and ground are sound, follow the manufacturer's procedure to determine whether sensor A or its communication module has failed.

Common fixes

• Secure or clean the sensor A connector and repair damaged wiring.
• Restore a faulty power or ground connection to the sensor or its module.
• Repair an open or short in the network wiring to sensor A.
• Replace the failed turbocharger or supercharger speed sensor A or its communication module, as confirmed by testing.

Can I keep driving?

Drive only gently and avoid high boost, hard acceleration, and towing until the fault is diagnosed; the system may limit power and may be relying on estimated speed to protect the turbocharger or supercharger. Stop if the engine overheats, loses substantial power, or develops unusual turbocharger noises.