U0102

Lost Communication With Transfer Case Control Module

Car Fault Codes Network

Can you still drive? With care, short trips only

Who can fix it? Needs a workshop

Typical repair time 30 minutes – 4 hours

Typical cost SAR 100 to 4,500

What it means

Another module has stopped receiving messages from the transfer case control module over the CAN bus. This module exists on four-wheel-drive vehicles and controls switching between two-wheel drive, four-wheel drive and low range. When communication is lost, the drive mode may not change, and the cause is usually module power, its connector or the bus wiring; several U codes together point to a bus or battery problem.

Symptoms5

Four-wheel-drive light flashing or a warning light on.
Unable to shift into or out of four-wheel drive or low range.
Vehicle stuck in one drive mode.
Scan tool cannot communicate with the transfer case module.
Check engine light or other lights on with it on some vehicles.

Possible causes6

Weak battery or loose terminals.
Blown module power fuse.
Module connector corroded by water or mud, especially after water crossing or underbody washing.
Poor module ground.
Open or shorted bus wiring to the module.
Internal module failure.

How to diagnose5

Read codes from all modules; if many modules report lost communication, start with the battery and the bus, and if only the transfer case control module is missing, focus on it.
Try to communicate with the transfer case control module directly with a scan tool; no response points to lost power, ground or wiring to it.
Locate the transfer case control module from the manufacturer information, which exists only on four-wheel-drive vehicles with an electronic transfer case, and its location varies by make, then check its power fuse and measure power and ground at its connector.
Inspect the module connector for water, corrosion or loose terminals, and check the bus wiring to it.
Disconnect the battery and measure resistance between the CAN bus wires at the module connector, comparing with the manufacturer specification to find an open or short.

How to fix6

Charge or replace the battery, and clean and tighten its terminals.
Replace the blown fuse after finding why it blew.
Clean the module connector and repair the ground or damaged bus wiring.
Update the module software if the manufacturer has an update.
Replace the transfer case control module if proven faulty with good power and bus wiring, then program and code it to the vehicle.
Clear codes in all modules and 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 battery, fuse or corroded connector, rises with underbody wiring repairs, and is highest if the 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

Can I drive with this code?

Usually yes, with caution on normal roads, but do not rely on four-wheel drive in sand or off-road until it is fixed, because shifting may not work.

Why does the code appear after a desert trip or a water crossing?

Water and mud can reach the module connectors or wiring under the vehicle and cause corrosion or a short.

Does every vehicle have this code?

No. It only appears on vehicles with a transfer case controlled by its own module.

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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