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U0073 on 2017-2022 Kia Sportage: CAN Bus Communication Failure Causes and Fixes

Code U0073 on a 2017-2022 Kia Sportage means there's a major communication failure on the vehicle's main computer network (CAN bus). The most likely causes are wiring damage, a weak battery, or a poor ground connection. A full electrical diagnosis is required; simply replacing parts is not recommended.

23 minutes to read 2017-2022 Kia Sportage

Most Likely Cause

Damaged or Corroded CAN Bus Wiring

Est. Time

3.8 hrs

DIY Doable?

🔧 Shop

Shop Labor

$250 – $2400

Parts Price

$10 – $1500

🚫 Do not drive — Continued driving is not recommended. The loss of communication between critical modules like the ABS, power steering, and engine controller can cause unpredictable behavior, stalling, or the failure of safety systems without warning. The vehicle may enter a 'limp mode' with severely reduced power, or fail to start at all.

Key Takeaways

U0073 is a serious network failure code, not a simple part failure. Do not drive the vehicle.
Diagnosis must be methodical. Start with the easiest and most common causes: check the battery, fuses, and look for obvious wiring damage.
A professional scan tool is required to see which modules are offline, which is a critical diagnostic step.
The most likely cause is a physical problem with the wiring, a bad connection, or an unstable power supply.
Do not replace expensive control modules unless they have been definitively identified as the source of the network failure through a process of elimination.

U0073 stands for 'Control Module Communication Bus 'A' Off'. In your Kia Sportage, this means the primary communication network, known as the Controller Area Network (CAN bus), has stopped working. This network is like the vehicle's nervous system, allowing critical modules like the Engine Control Module (ECM), Transmission Control Module (TCM), ABS, and Body Control Module (BCM) to exchange data. When this network goes down, these essential components can no longer talk to each other, leading to widespread and often unpredictable system failures, such as multiple warning lights and loss of safety features.

What's Unique About the 2017-2022 Kia Sportage

The fourth-generation (QL) Kia Sportage is a modern vehicle with dozens of interconnected electronic modules. While the U0073 code is generic, on this platform it often points to issues in the physical wiring harness or a failing control module. Owners have reported seemingly unrelated electrical failures, such as a melted fuse in the main battery harness causing a total loss of power, which can also trigger network codes like U0073. A key area of concern is the Smart Junction Box (SJB), which integrates the Body Control Module (BCM). A failing SJB can cause a cascade of communication errors and electrical faults. The diagnostic process is not about a single known faulty part, but rather a methodical search for the break in the communication line, which could be anywhere in the vehicle.

Professional service recommended: Diagnosing a network communication failure requires specialized tools like an oscilloscope and a professional scan tool that can view network data, as well as access to vehicle-specific wiring diagrams. It is a complex and time-consuming process that often goes beyond the scope of DIY repair. Technicians will need to isolate modules and test network integrity to pinpoint the fault.

Symptoms You May Notice

Multiple warning lights illuminated on the dashboard at once (Check Engine, ABS, Traction Control, EPS, Airbag)
Loss of power steering (EPS warning light on)
Instrument cluster gauges dropping to zero or behaving erratically
Failure of electrical accessories like power windows, radio, or climate controls
Transmission may shift harshly or get stuck in one gear ('limp mode')
Engine may not start (no-crank) or may stall unexpectedly
Vehicle enters 'limp mode' with reduced power and RPM limited to 1800-2000
Brake warning light illuminated

⚠️ Don't Waste Money on the Wrong Fix

Replacing a single control module (like the ECM or BCM) without confirming it is the source of the network failure. The code often means that module *can't communicate*, not that it is necessarily broken.
Replacing the instrument cluster because the gauges are acting erratically. The cluster is usually just reporting the data it's receiving (or not receiving) from the network.
Overlooking a weak battery or poor charging system performance, which is a frequent and simple-to-fix root cause.

Most Likely Causes

Damaged or Corroded CAN Bus Wiring 🔴 High Probability Wiring harnesses can be susceptible to damage from vibrations, improper repairs, rodent intrusion, or water leaks. Connectors in exposed areas, like near the wheel wells or undercarriage, can suffer from water intrusion and corrosion, disrupting the CAN signal.
How to confirm: Perform a detailed visual inspection of the main wiring harnesses in the engine bay, under the dashboard, and near the fuse boxes. Look for chafed, pinched, or chewed wires. Check the resistance between CAN High (Pin 6) and CAN Low (Pin 14) at the OBD-II port with the battery disconnected; it should be approximately 60 ohms. A reading of 120 Ohms suggests a break in the circuit or a missing terminating resistor. A reading near 0 Ohms indicates a short circuit.
Typical fix: Repair the damaged section of the wiring harness. If a connector is corroded, it may need to be cleaned with a specialized contact cleaner or replaced entirely.
Est. part cost: $10-$100
Weak or Failing Battery / Poor Power Supply 🟡 Medium Probability → Shop Vehicle Battery Modern vehicles are highly sensitive to voltage. A weak battery can provide enough power to crank the engine but may drop below the threshold required for all control modules to initialize and communicate properly, especially during startup. This is a very common trigger for network communication codes.
How to confirm: Test the battery voltage with a multimeter. A healthy battery should read at least 12.4 volts at rest and maintain voltage above 10 volts while cranking. Check that the alternator is charging correctly (typically 13.8-14.5 volts with the engine running).
Typical fix: Recharge or replace the vehicle's battery. Ensure battery terminals are clean and tight.
Est. part cost: $150-$300
Faulty Control Module (e.g., BCM/SJB, ABS) 🟡 Medium Probability Any single module on the CAN network can fail internally, causing it to either stop communicating or broadcast disruptive signals that take down the entire network. On the Sportage, the Smart Junction Box (SJB), which contains the Body Control Module (BCM), is a known point of failure that can cause widespread electrical issues and communication codes.
How to confirm: This requires a professional scan tool. The diagnostic process involves disconnecting one module at a time and re-checking if communication is restored to the other modules. If the network comes back online after unplugging the ABS module, for example, then the ABS module is the likely culprit. A failing SJB may also cause parasitic battery drain.
Typical fix: Replace the faulty control module. A new module, especially the SJB/BCM, will require programming by a dealership or a qualified shop to work with the vehicle's specific VIN and options. Common SJB part numbers include 91950-D9650 (2018-2019) and 91955-D9660 (2020-2022).
Est. part cost: $400-$1500+
Poor Ground Connection ⚪ Low Probability Ground straps and connection points can corrode or become loose over time, creating high resistance and causing intermittent electrical issues for one or more modules. Key ground points are located in the engine bay and under the dashboard near the fuse panel.
How to confirm: Visually inspect and physically check the main ground points for the engine, chassis, and under the dashboard. Use a multimeter to check for voltage drops between the battery negative terminal and various ground points on the chassis and engine block. A good ground should show minimal voltage drop.
Typical fix: Clean the contact surfaces of the ground connection with a wire brush and tighten the bolt securely. Apply dielectric grease to prevent future corrosion.
Est. part cost: $1-$10

Rare But Worth Checking

Faulty Aftermarket Electronics: Improperly installed aftermarket head units, remote starters, or alarms can tap into CAN bus wires incorrectly, causing interference that disrupts network communication. If the problem started after a new accessory was installed, this should be the first suspect. The CAN bus wires are often accessed behind the radio for these installations.
Software Glitch / Required Update: While no specific TSB links U0073 to a software bug on this model, other Kia TSBs show that CAN signal processing errors can sometimes be fixed with a module software update. For example, TSB ELE299 addresses a software update for the Smart Junction Block for false brake light warnings on 2020-2022 models. This indicates that module software can be a source of communication-related issues.
Faulty Accessory Tow Hitch Wiring Harness: Kia has issued recalls (NHTSA 22V703000) for tow hitch harnesses that can short circuit due to moisture and debris accumulation on the module's circuit board, potentially causing a fire. While not directly linked to U0073, such a short circuit on a module connected to the vehicle's electrical system could potentially disrupt network communication.

Diagnosis Steps

Check Battery Health: Start with the basics. Ensure the battery is fully charged (12.4V+ at rest) and the terminals are clean and tight. Test the battery under load and verify the charging system is working (13.8-14.5V).
Scan for All Codes: Use a professional-grade scanner to read codes from ALL modules, not just the engine controller. Note which modules are not responding. This is critical for narrowing down the fault.
Inspect Fuses: Check all related fuse boxes (in the engine bay and inside the cabin) for any blown fuses, particularly those labeled for ECU, BCM, ABS, Cluster, or other control units.
Check CAN Bus Resistance: With the battery disconnected, measure the resistance between Pin 6 (CAN-H) and Pin 14 (CAN-L) on the OBD-II port. A healthy network should read approximately 60 Ohms. A reading of 120 Ohms suggests a break in the circuit or a faulty terminating resistor. A reading near 0 Ohms indicates a short circuit between the CAN lines.
Visual Inspection: Thoroughly inspect all visible wiring harnesses for signs of damage, chafing, corrosion, or rodent activity. Pay close attention to harnesses in the engine bay, under the dash, and where they pass through the firewall.

Parts You'll Likely Need

Vehicle Battery — A weak or failing battery is a common cause of low voltage, which can disrupt module communication during startup.
Trusted brands: Bosch, Interstate, DieHard
OEM price range: $200-$350
Aftermarket price range: $150-$300
Wiring Harness Repair Supplies — If the fault is a broken or corroded wire, repairing the harness is the most common fix. This is not a specific part but a collection of supplies.
OEM price range: $10-$50
Aftermarket price range: $10-$50
Control Module (ABS, BCM, etc.) — If a specific module is identified as faulty and pulling down the network, it will need to be replaced. The specific module varies depending on the diagnostic results.
Trusted brands: Kia (OEM)
OEM price range: $400-$1500+

Related Codes That Often Appear With This One

U0100 — Lost Communication With ECM/PCM
U0121 — Lost Communication With Anti-Lock Brake System (ABS) Control Module
U0140 — Lost Communication With Body Control Module (BCM)
P1326 — Knock Sensor Detection System. While not a communication code, this code puts the vehicle in limp mode, which can sometimes be confused with or occur alongside network failure symptoms.

Technical Service Bulletins (TSBs) & Recalls

TSB ELE299: Addresses a software update for the Smart Junction Block (SJB) on 2020-2022 models for a false 'Check brake light' warning, showing that software updates can fix module communication issues.
Product Improvement Campaign PI1802: Provides a software update to install the Knock Sensor Detection System (KSDS) to protect the engine. While not for U0073, it is a critical software update for this platform that can cause limp mode and warning lights, sometimes confused with network issues.

Platform-Specific Known Issues

Smart Junction Box (BCM) Failure: The Smart Junction Box (SJB), which houses the Body Control Module (BCM), is a known failure point. A faulty SJB can cause a wide array of electrical gremlins, including parasitic battery drain, flickering lights, and communication codes like U0140 and U0073. Replacement requires a part with a matching OEM number (e.g., 91950-D9650) and dealer programming.
Electronic problems in the new Kia Sportage: A forum user describes an experience with a new Sportage where multiple errors appear on the dash, the electric brake engages, and the car loses power. The dealer repeatedly replaced wiring harnesses and control units, indicating the complexity and potential for recurring CAN bus issues.

Mechanic-Grade Diagnostic Values

CAN Bus Network Resistance — expected: ~60 Ω (Ohms) between Pin 6 (CAN-H) and Pin 14 (CAN-L) at the OBD-II port with the battery disconnected.. Failure: A reading of ~120 Ω indicates an open circuit or one of the two terminating resistors is offline. A reading near 0 Ω indicates a short between the CAN-H and CAN-L wires.
CAN Bus Voltage (Key On, Engine Off) — expected: CAN-H (Pin 6 to Ground) should be ~2.6V. CAN-L (Pin 14 to Ground) should be ~2.4V. These are average readings on a multimeter; an oscilloscope will show signals fluctuating between 1.5V and 3.5V.. Failure: No voltage, or voltage that is stuck high or low, indicates a short to power or ground on the respective line.
CAN Bus Baud Rate — expected: 500k. Failure: Not directly measured, but incorrect configuration in an aftermarket device can disrupt the network.

Scan Tool Commands That Help

Kia GDS (Global Diagnostic System): Vehicle Software Management / Special Function — Used for programming a new or used Body Control Module (BCM/SJB) to the vehicle's VIN and key configuration. This is a mandatory step after replacement.
Kia GDS (Global Diagnostic System): Actuation Tests / Module Communication Status — To actively poll all modules on the CAN network and see which ones are responding and which are not. This helps isolate the source of the communication failure without having to physically disconnect each module one-by-one initially.

Wiring & Ground Locations

OBD-II / Data Link Connector — Below the left side of the driver's dashboard.. This is the primary access point for testing the entire CAN network. Pin 6 (CAN-H) and Pin 14 (CAN-L) are used for resistance and voltage checks.
Smart Junction Box (SJB) / BCM — Integrated with the interior fuse panel, located behind the glove box.. This is a central communication hub and a common failure point. A fault here can take down the entire network. It also houses fuses for multiple modules.
Multipurpose Check Connector — Located in the engine room fuse & relay box.. This connector serves as another junction point for CAN lines, providing an alternative location to test network segments if the OBD-II port gives ambiguous readings.
Transaxle Range Switch Connector (C301) — On top of the transmission housing.. While primarily for the starting system, wiring to this switch is part of a larger harness. Damage or corrosion in this area could potentially affect nearby CAN bus wiring.

OEM Part Supersession History

91950-D9650 → N/A — Model Year Specific Part
Heads up: This Smart Junction Box (BCM) is typically found on 2018-2019 Sportage models.
91955-D9660 → N/A — Model Year Specific Part
Heads up: This Smart Junction Box (BCM) is typically found on 2020-2022 Sportage models, which correspond to the facelift. Do not interchange with the earlier part number.

Model Year Variations Within This Range

2019-2022: A mid-cycle facelift was introduced for the 2019/2020 model year, which included revised front/rear bumpers, new headlamp/taillight designs, a revised instrument cluster, and new powertrain options like a mild-hybrid diesel in some markets. These changes introduced different part numbers for electronic modules like the Smart Junction Box (BCM).

Diagnostic Flowchart

The U0073 code indicates a 'Control Module Communication Bus A Off' condition. Start by verifying battery health and scanning all modules, as low voltage or a single 'noisy' module can crash the entire CAN network.

Does the battery maintain >10V during cranking and 13.8-14.5V while running?

→ Replace the battery or alternator. Modern Sportage electronics are highly sensitive to voltage drops during module initialization, which frequently triggers U0073.

Disconnect the battery. Measure resistance between Pin 6 (CAN-H) and Pin 14 (CAN-L) at the OBD-II port. What is the reading?

Are there specific symptoms like erratic gauges, parasitic drain, or a 'Check Brake Light' warning (ref: TSB ELE299)?

Does the vehicle have a Smart Junction Box (SJB/BCM) part number like 91950-D9650 or 91955-D9660?

→ The SJB is a known high-failure point on 2017-2022 Sportages. If communication is restored when the SJB is bypassed, replace and perform dealer programming per TSB ELE299.

If the network is still down, disconnect the ABS Module connector. Does the U0073 code clear or do other modules return to 'Online' status?

→ The ABS module is internally shorted, 'pulling down' the CAN bus. This is a common shared failure with the platform-mate Hyundai Tucson. Replace the ABS unit.

Inspect the main ground points in the engine bay and under the dashboard near the fuse panel. Is there corrosion or loose bolts?

→ Clean contact surfaces with a wire brush, tighten bolts, and apply dielectric grease to prevent high resistance that disrupts module communication.

→ Perform a 'pin-out' test of the CAN wiring between the SJB and the ECU. If wiring is intact, the issue may be a software conflict requiring a KSDS update (PI1802) or a faulty ECU.

If the network is still down, disconnect the ABS Module connector. Does the U0073 code clear or do other modules return to 'Online' status?

→ The ABS module is internally shorted, 'pulling down' the CAN bus. This is a common shared failure with the platform-mate Hyundai Tucson. Replace the ABS unit.

Inspect the main ground points in the engine bay and under the dashboard near the fuse panel. Is there corrosion or loose bolts?

→ Clean contact surfaces with a wire brush, tighten bolts, and apply dielectric grease to prevent high resistance that disrupts module communication.

→ Perform a 'pin-out' test of the CAN wiring between the SJB and the ECU. If wiring is intact, the issue may be a software conflict requiring a KSDS update (PI1802) or a faulty ECU.

→ A 120 Ohm reading indicates a break in the CAN circuit or a missing terminating resistor. Inspect the wiring harness for rodent damage or chafing, common in the engine bay of this platform.

→ A short circuit exists between CAN High and CAN Low. Inspect for pinched wires near the wheel wells or undercarriage where water intrusion is common.