NetworkU0646

Serious

Severity: Serious - have it checked soon

Lost communication with motor electronics coolant pump 'A'

11 brands affected · Description from Toyota data.

Key terms: Control module: a small computer that runs one part of the car

Safety: This code relates to engine cooling or temperature. Overheating can damage the engine.

1What it means in plain English

Control modules in the car cannot communicate with each other over the vehicle network.

2Common causes

Wiring or connector fault on the communication bus
Faulty control module
Low battery voltage or poor ground
Water ingress in a connector or module
Aftermarket device interfering with the bus

3Can I drive?

Serious · drive with care

The car may run normally or may not run at all. If the module that has lost communication controls steering, brakes, park brake, charging or engine cooling, drive only if those systems feel normal; stop safely if the steering becomes heavy, a brake warning appears, or the engine temperature climbs. If the car will not start or runs badly, have it towed.

This page gives general information. It is not professional advice. For a definite diagnosis and a repair quote, ask a qualified mechanic to inspect the car.

4Brand data 11

Brand	Code	Description	System
Ashok Leyland CV	U0646	No description available	Network
Daewoo	U0646	No description available	Network
EOBD	U0646	Kaotatud side mootori elektroonika jahutuspumbaga 'A' Brand	Network
Ford	U0646	No description available	Network
GM	U0646	No description available	Network
Holden	U0646	No description available	Network
Honda	U0646	No description available	Network
Opel	U0646	No description available	Network
Peugeot	U0646	No description available	Network
Saab	U0646	No description available	Network
Toyota	U0646	Lost communication with motor electronics coolant pump 'A' Brand	Network

Legend: SAE is the generic J2012 description; Brand is text taken from that manufacturer’s data. Manufacturer rows keep the wording and language of the source data, and non-English text is tagged so screen readers pronounce it correctly.

5Related codes

Browse Uxxx codes or U064xx codes.