NetworkU1233

Serious

Severity: Serious - have it checked soon

Reversible alternator

13 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 the charging system. The battery may go flat and the car may stall.

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 13

Brand	Code	Description	System
Mercedes-Benz	U1233	No description available	Network
Chery	U1233	Vehicle Control Unit (VCU) CAN 0 network segment lost communication with IBS Brand	Network
Daewoo	U1233	Loss of serial communications for class 2 devices Brand	Network
EOBD	U1233	Vendbar generator Brand	Network
GM	U1233	Loss of serial communications for class 2 devices Brand	Network
Holden	U1233	Invalid Data Received From Generator Control Module Brand	Network
Opel	U1233	Loss of serial communications for class 2 devices Brand	Network
Peugeot	U1233	No description available	Network
Saab	U1233	Loss of serial communications for class 2 devices Brand	Network
Smart	U1233	No description available	Network
Sprinter	U1233	No description available	Network
Subaru	U1233	No description available	Network
Toyota	U1233	Reversible alternator 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.

5Extended variant codes 2

These 7-character codes are manufacturer-specific variants of U1233 and may be reported by some scan tools.

Brand	Code	Description	System
SsangYong	U123383	CAN communication: Electrical Brake Unit (EBU) checksum error (300) Brand	Network
Mercedes-Benz	U123388	Die Kommunikation mit dem Benutzerschnittstelle-CAN-Bus 2 hat Funktionsstörung Brand	Network

6Related codes

Browse Uxxx codes or U123xx codes.