U0100 on 2016-2020 Kia Sorento: Lost Communication with ECM/PCM Causes and Fixes

What's Unique About the 2016-2020 Kia Sorento

For the 2016-2020 Kia Sorento (the third generation, or UM), there are no widely reported, specific defects or recalls that consistently cause the U0100 code. However, this generation is known for using soy-based wire insulation, which can attract rodents and lead to chewed wires, a potential cause of this communication fault. Troubleshooting a U0100 on a Sorento follows a general, logical diagnostic path common to most modern vehicles, starting with the most basic electrical components first. A notable change for the 2019 model year was the introduction of an Integrated Gateway Power Module (IGPM) on some trims, which centralizes power distribution and could be a factor in network-wide issues.

Symptoms You May Notice

• Check Engine Light is on
• Vehicle will not start, or cranks but does not fire
• Engine stalls intermittently while driving
• Reduced engine power or 'limp mode'
• Multiple warning lights on the dashboard (e.g., ABS, Traction Control, Power Steering)
• Transmission may not shift correctly or may default to a single gear
• Erratic or rough idle
• Complete loss of power to gauges and accessories in some cases

Most Likely Causes

1. Weak or Faulty Battery 🔴 High Probability → Shop Vehicle Battery Modern vehicles like the Sorento are highly dependent on stable voltage. A battery that is failing or has low voltage (dropping below 10V during cranking) can cause unpredictable communication errors between modules before it's completely dead.
   How to confirm: Test the battery voltage with a multimeter. A healthy, fully charged battery should read approximately 12.6 volts with the engine off. Anything below 12.2 volts suggests a weak battery. A load test is the most definitive way to confirm a battery's health.
   Typical fix: Clean battery terminals and cable ends of any corrosion, or replace the battery if it fails a load test.
   Est. part cost: $150-$300
2. Poor Ground Connections 🟡 Medium Probability Corrosion or physical damage can affect the main ground straps from the battery to the chassis and from the engine to the chassis. A bad ground for the ECM/PCM is a common point of failure and prevents it from operating correctly.
   How to confirm: Visually inspect the main ground cables for tightness, corrosion, or breakage. Key locations include the strap from the negative battery terminal to the inner fender and the strap from the engine block to the frame rail. 🎬 See how to locate and inspect your car's ground cables Use a multimeter to check for voltage drop between the battery negative post and the engine block/chassis; it should be less than 0.2 volts.
   Typical fix: Clean the contact points of ground straps with a wire brush and ensure they are securely fastened. Replace any corroded or broken ground cables.
   Est. part cost: $20-$50
3. Damaged Wiring or Connectors 🟡 Medium Probability
   How to confirm: Visually inspect the wiring harness going to the Engine Control Module (ECM) for any signs of chafing, melting, or rodent damage (a known issue due to soy-based wiring). Pay close attention to where the harness may rub against the engine, frame, or brackets. Unplug the ECM connectors (with the battery disconnected) and check for corroded, bent, or pushed-out pins.
   Typical fix: Repair the damaged section of the wiring harness. Clean or replace connector pins as needed. In cases of rodent damage, extensive harness repair may be necessary, with costs ranging from $200 to over $2,500.
   Est. part cost: $10-$1000+
4. Faulty Engine Control Module (ECM/PCM) ⚪ Low Probability → Shop Engine Control Module (ECM)
   How to confirm: This is a last resort after all other possibilities (power, ground, wiring) have been exhaustively checked and confirmed to be good. A professional shop can perform tests to see if the ECM is truly offline and not responding to scan tool queries. The presence of code P0605 (Internal Control Module Read Only Memory Error 🎬 Watch: Professional ECM diagnostics for a Kia Sorento no-start) is a strong indicator of internal ECM failure.
   Typical fix: Replace the ECM. This requires programming the new module to the vehicle's VIN and security system.
   Est. part cost: $800-$1500

Rare But Worth Checking

• Aftermarket Device Interference: Poorly installed remote starters, alarms, or even plug-in insurance trackers can tap into the CAN bus wiring and cause communication failures. One owner reported that an improperly wired aftermarket stereo triggered the code. If you have any such devices, they should be the first thing you disconnect during diagnosis.
• CAN Bus Network Failure: A short or open in the main CAN bus wiring itself can bring down communication. This is rare and difficult to diagnose, often requiring an oscilloscope to check the network signals for the proper waveform. Kia has issued TSBs like ELE200 for other models regarding CAN wiring inspection, highlighting the need for careful checks of these circuits.
• Faulty Smart Junction Box / IGPM: On newer models (especially 2019+), an internal failure in the Smart Junction Box or Integrated Gateway Power Module (IGPM) can cause widespread communication issues, including U0100. This module acts as a central hub for power and data, and its failure can mimic a CAN bus or ECM fault.

Diagnosis Steps

1. Read all codes from all modules using a professional-grade scan tool. Note which modules are reporting the U0100 code and which modules are not communicating at all.
2. Check Battery Health: Test the battery's state of charge (should be ~12.6V) and perform a load test. Ensure battery terminals are clean and tight. A low-voltage condition is the most common trigger.
3. Inspect Fuses: Check all fuses related to the ECM/PCM and other control modules in both the under-hood and interior fuse boxes. A blown fuse points to a short circuit that needs to be found.
4. Inspect Grounds: Visually inspect and test the main battery-to-chassis and engine-to-chassis ground connections for corrosion and tightness. Perform a voltage drop test on the ground circuit; it should be under 0.2V.
5. Inspect ECM Wiring: With the battery disconnected, carefully inspect the wiring harness and connectors at the ECM for any visible damage, corrosion, or loose pins. Check for signs of rodent damage or chafing against other components.
6. Check for Aftermarket Devices: If any aftermarket electronics (remote starter, alarm, stereo, OBD-II dongle) are installed, disconnect them completely and re-test.
7. CAN Bus Resistance Check: With the battery disconnected, measure the resistance of the CAN bus at the OBD-II port (pins 6 and 14). It should be approximately 60 ohms. A reading of 120 ohms indicates an open circuit or a missing terminating resistor, while a reading near 0 ohms indicates a short circuit between the CAN High and Low lines.
8. Professional Diagnosis: If the steps above do not reveal the cause, the vehicle should be taken to a qualified technician who can perform advanced network diagnostics with an oscilloscope and verify ECM power/ground directly at the module connector.

Parts You'll Likely Need

• Battery — A weak or failing battery is the most common trigger for network communication codes on modern vehicles.
  Trusted brands: Interstate, DieHard, ACDelco, Kia (OEM)
  OEM price range: $200-$350
  Aftermarket price range: $150-$300
• Engine Control Module (ECM/PCM) (OEM #Varies by VIN and engine type (e.g., 39111-2GTE1, 39101-2GTE1 for some 2.0T models). Always verify with VIN.) — If all power, ground, and wiring are confirmed to be good, the module itself may have failed internally. This is a low-probability cause.
  Trusted brands: Kia (OEM), Flagship One (Remanufactured), Solo Auto (Remanufactured)
  OEM price range: $1000-$1500
  Aftermarket price range: $500-$900 (Remanufactured)
• Ground Strap — The engine-to-chassis or battery-to-chassis ground straps can corrode or break, interrupting power to the ECM and other modules.
  Trusted brands: Kia (OEM), Dorman
  OEM price range: $30-$60
  Aftermarket price range: $15-$40

Related Codes That Often Appear With This One

• U0101 — Lost Communication with TCM. If both U0100 and U0101 are present, it strongly suggests a network-wide issue (like a bad battery, faulty gateway, or CAN bus fault) rather than a single failed module.
• Multiple other U-codes — If many modules are reporting lost communication with each other (e.g., U0121 - Lost Comms with ABS, U0140 - Lost Comms with BCM), it points towards a central network problem or a faulty gateway module that routes messages.
• P0562 — System Voltage Low. This code often accompanies U0100 and strongly indicates that a weak battery or charging system problem is the root cause of the communication failure.

Technical Service Bulletins (TSBs) & Recalls

• TSB ELE200: While for a different model (Stinger),

Platform-Specific Known Issues

• Corroded Ground Strap Causing No-Start and U0100: → Shop Engine Ground Strap An owner of a 2017 Sorento on a forum reported a no-crank, no-start condition accompanied by the U0100 code. After checking the battery and fuses, the cause was found to be a severely corroded main ground strap between the engine and the chassis. Cleaning the contact points and replacing the strap resolved all issues.

Mechanic-Grade Diagnostic Values

• CAN Bus Resistance — expected: Approximately 60 Ω (measured between Pin 6 and Pin 14 of the OBD-II port with battery disconnected).. Failure: A reading of 120 Ω indicates an open circuit or a failed terminating resistor in one module. A reading near 0 Ω indicates a short between the CAN High and CAN Low wires.
• CAN High (CAN-H) Voltage — expected: ~2.5V to 3.5V (Key On, Engine Off, measured at OBD-II Pin 6 to chassis ground).. Failure: Voltage significantly outside this range indicates a short to power or ground on the CAN-H line.
• CAN Low (CAN-L) Voltage — expected: ~1.5V to 2.5V (Key On, Engine Off, measured at OBD-II Pin 14 to chassis ground).. Failure: Voltage significantly outside this range indicates a short to power or ground on the CAN-L line.
• ECM Power Supply Voltage — expected: 12.0V - 14.5V (measured at the ECM power supply pins with Key On).. Failure: Voltage drop below 10V during cranking or significant deviation from battery voltage suggests a power supply issue to the module.
• ECM Ground Circuit Voltage Drop — expected: < 0.2V (measured between the ECM ground pins at the connector and the negative battery terminal).. Failure: A reading higher than 0.2V indicates high resistance in the ground circuit, which can cause the module to malfunction.

Scan Tool Commands That Help

• Kia GDS (Global Diagnostic System) or equivalent J2534 tool: Network Scan / Topology Check — This is a primary step to get a visual map of all control modules on the CAN bus and see which ones are online (green), offline (red), or reporting codes. It quickly identifies if only the ECM is offline or if it's a wider network problem.
• Kia GDS (Global Diagnostic System) or equivalent J2534 tool: ECU Upgrade / Reprogramming — This function is mandatory after replacing the ECM to write the vehicle's VIN and immobilizer data to the new module. It can also be used to apply any available software updates that might address communication glitches.

Wiring & Ground Locations

• Main Engine Ground — Typically a braided strap running from the engine block (often near the alternator or starter) to the chassis frame rail on the driver's side.. This is a primary ground path for the entire powertrain. Corrosion or looseness here can cause a floating ground, leading to intermittent power and communication loss for the ECM.
• Battery Negative to Chassis Ground — A thick black cable from the negative battery terminal directly to the inner fender or shock tower.. This is the master ground for the entire vehicle's electrical system. Any fault here will cause widespread, unpredictable electrical problems, including U-codes.
• ECM/PCM Connector — The ECM is typically located in the engine bay, often on the driver's side firewall or attached to the air filter housing. It has large multi-pin connectors.. This is the direct interface for all ECM power, ground, and CAN bus signals. The pins for CAN-H, CAN-L, power, and ground must be tested here to confirm the fault isn't at the module's connection point.
• CAN Junction Block — Often located behind the driver's side kick panel or integrated into the under-dash fuse box (Smart Junction Box).. This is a central point where CAN bus wires from various modules meet. A loose connection or corrosion in this block can sever communication for multiple modules at once.

Real Owner Repair Stories

• Motor Vehicle Maintenance & Repair Stack Exchange (2016 Kia Sorento) — Vehicle would not start, suspected fried ECM.
  ❌ Tried (didn't work) Considering immediate ECM replacement.
  ✅ What actually fixed it The problem occurred after the owner's boyfriend was installing an aftermarket stereo system. The expert consensus was that the stereo was likely wired incorrectly, causing a short or interference on the data bus, and that this should be investigated before replacing the ECM.

Model Year Variations Within This Range

• 2019-2020: The 2019 model year refresh introduced a more powerful 3.3L V6 engine option with an 8-speed automatic transmission, compared to the previous 6-speed. Higher trims also received an updated infotainment system and the potential for an Integrated Gateway Power Module (IGPM), which centralizes some electrical functions and could be a diagnostic point not present on earlier 2016-2018 models.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Theta II Engine Rod Bearing Failure & Seizure 🔴 High — Common in 2.0L & 2.4L GDI engines, particularly 2016-2018 models. Can occur at various mileages, sometimes as low as 60,000 miles. (Ref: Subject to class-action lawsuits and a lifetime warranty extension if a Knock Sensor Detection System (KSDS) software update was performed.)
• Excessive Oil Consumption 🟠 Medium — Affects many 2.4L and 2.0T GDI engines. Often caused by stuck oil control rings. Owners report needing to add oil between changes. (Ref: No specific recall for oil consumption itself, but it is a known symptom related to the larger Theta II engine issues.)
• Engine Rattle from Timing Chain Tensioner 🟠 Medium — A rattling noise on cold startup is common, often traced to a faulty timing chain tensioner. Typically occurs between 30,000-60,000 miles. (Ref: Kia released an updated tensioner design to address the problem.)
• High-Pressure Fuel Line Leak 🔴 High — Affects 2016-2017 models with GDI engines. A leak can develop in the fuel line connected to the high-pressure pump. (Ref: Recall issued (e.g., NHTSA 18V907000) due to fire risk.)
• Rodent Damage to Wiring 🟡 Low — The soy-based coating on electrical wires can attract rodents, leading to chewed wires and various electrical faults.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used ECM from a reputable salvage yard can be a cost-effective option, but only if you have a confirmed plan for reprogramming. For wiring harnesses, a used section from a donor vehicle is often the only practical repair for extensive rodent damage, as a brand new harness can be prohibitively expensive ($2,500+).

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For an ECM: Ensure the donor vehicle was not in a flood or fire. Get the VIN of the donor car to verify compatibility and check its history.
• For a wiring harness: Inspect thoroughly for any signs of cuts, melted sections, or previous repairs. Ensure all connectors are intact with no broken locking tabs or corroded pins.

OEM-only on this vehicle (don't cheap out):

• Engine Control Module (ECM/PCM): While remanufactured units exist, an OEM module (new or used) is the safest bet for ensuring software compatibility. Avoid no-name clones. Programming is mandatory regardless of source.

Aftermarket brands forum-validated for this vehicle:

• Flagship One (Remanufactured ECM)
• Solo Auto (Remanufactured ECM)

Brands owners have reported issues with on this vehicle:

• Generic, unbranded ECMs from online marketplaces without a warranty or programming support.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0605 — Internal Control Module Read Only Memory Error; its presence strongly indicates the U0100 is caused by internal ECM failure rather than wiring.

Frequently Asked Questions