U0002

High Speed CAN Communication Bus Performance

Car Fault Codes Network

Can you still drive? With care, short trips only

Who can fix it? Needs a workshop

Typical repair time 1 hour – 5 hours

Typical cost SAR 150 to 3,000

What it means

A module has detected that the high-speed CAN bus is working but not correctly: messages arrive corrupted, intermittent or with repeated errors, without a complete loss. The usual cause is a weak intermittent connection at a connector or wire, unstable battery voltage, or a module disturbing the bus. The code is usually stored in another module, and together with other U codes it points to a bus or power problem.

Symptoms5

Warning lights that come and go with no clear pattern.
Some gauges or indicators drop out and come back.
Occasional erratic transmission shifting.
Intermittent lost-communication codes stored in several modules.
Sometimes no clear symptom other than the stored code.

Possible causes6

Loose or corroded connector causing an intermittent connection.
Low or unstable voltage from a weak battery or alternator.
Partly damaged bus wire or worn insulation affected by vibration.
Electrical noise from added accessories such as trackers or alarms.
Moisture or water inside a connector or module.
A module working incorrectly and sending bad messages.

How to diagnose6

Read codes from all modules and note where intermittent communication codes repeat.
Check the battery and charging system and make sure voltage stays stable while running with loads on.
Gently wiggle connectors and wiring while watching communication on the scan tool to find the intermittent point.
With the battery disconnected, measure resistance between the two bus wires: a healthy bus has two 120-ohm termination resistors and reads about 60 ohms; about 120 ohms points to an open or a missing resistor, and near zero points to the two wires shorted together.
Check any accessories plugged into the diagnostic port or tapped into the bus wiring and disconnect them temporarily.
Check areas exposed to water, such as under the carpet, near the doors and near the windshield.

How to fix6

Fix any battery or charging problem.
Clean and tighten connectors, and replace loose terminals.
Repair the damaged wire or worn insulation.
Remove the accessories causing noise or reinstall them correctly.
Update the software of the faulty module, or replace and program it if proven faulty.
Clear the codes and drive in different conditions to confirm the code does not return.

Repair cost

0–500

500–2,000

2,000–5,000

5,000+

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low for a connector or battery, rises because intermittent faults take longer to trace, and is highest if a module must be replaced and programmed.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions

How is this code different from U0001?

U0001 describes a general bus fault, while this code means the bus works but with errors or dropouts. It is usually an intermittent fault that is harder to trace.

Can electrical accessories cause this code?

Yes. Trackers, alarms or plug-in devices left in the diagnostic port can disturb the bus, so disconnecting them is one of the first checks.

Why does the code go away and come back?

The cause is often a weak connection affected by heat, vibration or moisture, so the fault only shows up under certain conditions.

This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

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