U0648: Lost Communication With Motor Electronics Coolant Pump C

What it means

A control module has stopped receiving expected network messages from motor electronics coolant pump C. The effect on motor electronics cooling depends on the vehicle's system design.

At a glance

• Usually lights the warning light of the system that lost communication
• The engine or gearbox may go into limp mode

How it works

Motor electronics coolant pump C circulates coolant for the portion of the cooling system assigned to that pump. U0648 sets when a control module no longer receives expected network messages from pump C, making its status unavailable and potentially affecting motor-electronics cooling.

Common causes

Most likely first.

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

Symptoms

• Warning light or message related to the affected system
• Motor electronics cooling or vehicle performance may be affected

How to diagnose it

1. Scan all modules and save freeze-frame data, noting motor-electronics temperature and any pump C or cooling-system codes.
2. Check live data for pump C status and relevant temperatures to see whether the pump is unreported or heat is increasing.
3. With the vehicle safely powered down as specified by the manufacturer, inspect pump C’s connector and visible network wiring for looseness, corrosion, or damage.
4. Check pump C’s module power and ground circuits against the manufacturer’s specification.
5. Test the network wiring to pump C for opens or shorts using the vehicle wiring information.
6. If these circuits pass, confirm network communication and pump module operation before replacing it.

Common fixes

• Reconnect or clean the motor electronics coolant pump C connector.
• Repair damaged network wiring to pump C.
• Restore the pump C module’s power or ground supply.
• Replace pump C if its wiring and supplies are sound but the module remains off the network.

Can I keep driving?

Stop safely if the vehicle shows a cooling warning, rising temperature, or reduced-power message, since continued driving can overheat motor electronics. Follow the vehicle’s instructions and arrange diagnosis before relying on the vehicle.