U0100 on 2018-2024 Volvo V90: Lost Communication With ECM/PCM Causes and Fixes

What's Unique About the 2018-2024 Volvo V90

The 2018-2024 Volvo V90 is built on the modern SPA (Scalable Product Architecture) platform, which has a very high electrical demand due to numerous interconnected modules. While older Volvos had well-known issues with the Central Electronic Module (CEM) causing communication faults, the SPA platform architecture is different. For these newer models, electrical stability is paramount. The U0100 code is frequently triggered by low voltage from an aging 12V main battery or a poor ground connection before it indicates a true module failure. Owners and technicians strongly advise starting diagnostics with the battery and grounds, as this is the most common and simplest fix.

Symptoms You May Notice

• Check Engine Light is on
• Vehicle will not start (cranks but no fire, or no crank at all)
• Engine stalls intermittently while driving
• Transmission may not shift correctly or get stuck in one gear ('Limp Mode')
• Loss of power and poor acceleration
• Multiple other warning lights may appear on the dashboard (e.g., ABS, SRS, Brake)
• Instrument cluster gauges (speedometer, tachometer) may stop working or go blank
• Headlights may flicker or dim, especially under electrical load.

Most Likely Causes

1. Weak or Failing 12V Battery 🔴 High Probability Modern Volvos on the SPA platform have a high electrical demand with many onboard computers that are sensitive to voltage drops. A battery that is even slightly weak or old can cause voltage drops during startup or when systems activate, disrupting network communication and triggering a U0100 code.
   How to confirm: Test the battery voltage with a multimeter. A healthy, resting AGM battery should be at ~12.6V. A reading below 12.2V suggests it is discharged or failing. A professional load test is the definitive way to confirm a battery's health.
   Typical fix: Recharge or replace the 12V main AGM battery. The battery management system (BMS) may need to be reset with a capable scan tool 🎬 See how to perform a battery reset on your Volvo. after replacement.
   Est. part cost: $250-$450
2. Corroded or Loose Battery Terminals/Ground Straps 🟡 Medium Probability The main engine-to-chassis and battery-to-chassis ground straps can corrode or loosen over time. This creates high resistance in the circuit, leading to intermittent voltage drops and communication problems that mimic a failing battery.
   How to confirm: Visually inspect the main battery terminals for white or green crust. Locate the main engine-to-chassis ground strap (a braided metal cable) and check for corrosion, fraying, or looseness at its connection points on the engine and body. A voltage drop test across the ground circuit should show less than 0.2V; anything higher indicates a problem.
   Typical fix: Disconnect the battery. Remove, clean with a wire brush, and re-secure all ground connection points until they are shiny. Replace any ground strap that is frayed or heavily corroded.
   Est. part cost: $20-$80
3. CAN Bus Wiring or Connector Issue ⚪ Low Probability While not common, wiring can be damaged by rodents, previous repairs, or chafing against a bracket. A single compromised wire in the network can take down communication. Water intrusion into a connector can also cause corrosion and network failure.
   How to confirm: This requires advanced diagnostics. A technician would use a wiring diagram and an oscilloscope to check for a valid signal on the CAN High and CAN Low wires at the OBD-II port or ECM connector. A resistance check of the CAN bus (should be ~60 Ohms with the battery disconnected) can also find issues.
   Typical fix: Repair the damaged section of the wiring harness or clean/replace the affected connector.
   Est. part cost: $5-$100 for wiring supplies

Rare But Worth Checking

• Faulty Engine Control Module (ECM): This is a common misdiagnosis. Control modules are robust and rarely fail. All other possibilities, especially power and ground issues, must be eliminated before condemning the ECM.
• Software Glitch: Occasionally, a communication issue can be resolved by a software update performed by a Volvo dealer. Check for any available Technical Journals (TJs) or software updates, especially if the problem is intermittent and no physical cause can be found.
• Faulty Gateway Module (VGM): The Vehicle Gateway Module acts as a router between the different CAN networks. A failure in this module can prevent the ECM from communicating with other systems. Diagnosis requires a Volvo-specific scan tool.

Diagnosis Steps

1. Read All Codes: Use an advanced OBD-II scanner to read codes from all modules, not just the engine. Note any other 'U' codes or power-related codes like P0562.
2. Check Battery Health: This is the most critical first step. Use a multimeter to check the resting voltage (should be ~12.6V). Perform a professional load test to confirm its health. Many auto parts stores offer this service for free.
3. Inspect Power and Grounds: Clean any corrosion from the battery terminals. Follow the negative battery cable to the chassis and ensure the connection is clean and tight. Locate the main engine-to-chassis ground strap and inspect it for corrosion or damage. Perform a voltage drop test on the ground circuit to confirm its integrity.
4. Check Fuses: Inspect all fuses related to the ECM, Gateway Module (VGM), and other control modules in the fuse boxes (engine bay and interior).
5. Visual Inspection of Wiring: Look for any obvious signs of wiring damage, such as rodent nests, chafing, or damage from previous repairs, particularly around the ECM, battery area, and main harness looms.
6. CAN Bus Network Test (Professional): If the above steps don't reveal the issue, the next step is to test the CAN bus itself. This involves measuring resistance between CAN-High and CAN-Low at the OBD-II port (should be 60 ohms with battery disconnected). An oscilloscope is used to check for a valid signal waveform.
7. ECM Diagnosis (Professional): Only after confirming the wiring, power, and grounds are good should the ECM be considered the problem. A technician can perform specific tests on the ECM's power, ground, and communication circuits before recommending replacement.

Parts You'll Likely Need

• 12V AGM Battery (OEM #31652945 (Varies by vehicle spec, confirm with VIN)) — The most frequent cause of network communication codes on modern, electrically-demanding vehicles like the V90.
  Trusted brands: Volvo (OEM), Bosch, Interstate, Deka
  OEM price range: $350-$450
  Aftermarket price range: $250-$350
• Engine Ground Strap (OEM #31439121 (Varies, confirm with VIN)) — A corroded or broken ground strap is a common and inexpensive cause of major electrical and communication faults that can mimic a failed module.
  Trusted brands: Volvo (OEM)
  OEM price range: $40-$80
  Aftermarket price range: $20-$50

Related Codes That Often Appear With This One

• U0101 — Lost Communication with TCM (Transmission Control Module). The TCM and ECM are on the same high-speed CAN bus and communicate constantly. A network-wide problem will often cause both codes to appear.
• U0155 — Lost Communication with Instrument Panel Cluster (IPC). If the network is down, the instrument cluster will also lose its data feed from the ECM, triggering this code.
• U0140 — Lost Communication with Body Control Module. On Volvos, this often refers to the CEM or VGM. A fault here points towards a more central network failure.
• P0562 — System Voltage Low. This code is a strong indicator that the root cause of the U0100 is a power supply issue, such as a failing battery or alternator, rather than a module or wiring fault.

Technical Service Bulletins (TSBs) & Recalls

• Volvo Technical Journal (TJ) 31895: Addresses various software-related issues and communication faults. A dealer can check if this or other software updates are applicable to your VIN and symptoms.

Platform-Specific Known Issues

• Dual Battery System: Many SPA-platform Volvos have a main 12V AGM battery in the rear and a smaller auxiliary/support battery in the engine bay. The support battery helps with the start/stop system and stabilizes voltage. A failure of this smaller battery can also contribute to widespread electrical and communication faults. Both batteries should be tested during diagnosis.

Mechanic-Grade Diagnostic Values

• CAN Bus Network Resistance — expected: 60 Ohms. Failure: A reading of 120 Ohms indicates a missing terminating resistor or a break in the wiring. A reading of 40 Ohms or less suggests an extra, unwanted resistor or a short circuit.
• CAN Bus Voltage (Key On, Engine Off) — expected: CAN High and CAN Low wires should both read approximately 2.5V.. Failure: Significant deviation from 2.5V on either line indicates a bias issue or a short on the bus.
• ECM Ground Circuit Resistance — expected: Below 1 Ohm. Failure: A reading higher than 1 Ohm between the ECM ground pins and a clean chassis ground point indicates a poor ground connection that can cause communication loss.
• Auxiliary/Support Battery Voltage — expected: ~12.6V or higher (fully charged). Failure: A voltage below 12.2V indicates the support battery is discharged or failing and can cause system voltage instability, leading to communication codes.

Scan Tool Commands That Help

• Volvo VIDA (Vehicle Information & Diagnostics for Aftersales): ECM Reload — This function is used to reinstall the existing software on the Engine Control Module. It can resolve software glitches or corruption that may be causing the U0100 code, especially if no physical faults are found. This is often performed before condemning the ECM itself.
• Volvo VIDA: VGM Recovery/Reload — According to Volvo Technical Journal TJ 36514, if the Vehicle Gateway Module (VGM) becomes unresponsive after a failed software download, it can disrupt all vehicle communication. VIDA may not even connect to the car. The TJ outlines a specific procedure involving a donor VGM to re-establish communication and perform a software reload on the original module.

Wiring & Ground Locations

• Central Electronic Module (CEM) — Located in the cabin, under the dashboard on the driver's side, near the steering column.. This module is a central hub for communication networks. It is notoriously susceptible to water damage from clogged sunroof drains, which can leak down the A-pillar and drip directly onto the CEM, causing corrosion and widespread communication failures, including U0100.
• Vehicle Gateway Module (VGM) — For SPA platform vehicles like the V90, the VGM is typically located in the passenger compartment. A Volvo TJ includes an image showing its location, often accessible from the cabin.. The VGM is the central router between different CAN bus networks. A software failure or internal fault in the VGM can completely isolate the ECM from the rest of the vehicle, directly causing a U0100 code.
• Main Engine Ground Strap — A braided metal cable connecting the engine block to the chassis/frame, typically visible in the engine bay.. Corrosion or looseness of this primary ground is a very common cause for intermittent and voltage-sensitive U-codes on SPA platform vehicles. It creates high resistance, destabilizing the electrical system that all modules rely on.

Model Year Variations Within This Range

• 2022-2024 (with Android Automotive OS): Vehicles with the Android Automotive Operating System (iCUP) are specifically mentioned in Technical Journals (like TJ 36514) regarding Vehicle Gateway Module (VGM) software failures. While the U0100 fault can occur on any year, the diagnostic path and potential for software-induced communication loss with the VGM are more formally documented for these later 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:

• Excessive Engine Oil Consumption (T5/T6 Engines) 🔴 High — Common enough to warrant a Volvo Extended Warranty Program (P10207/P10186) for piston/ring replacement on affected vehicles, typically under 8 years/100k miles. Often linked to piston ring design on 2.0L 'Drive-E' engines. (Ref: Quality Bulletin P10186 / P10207)
• Premature/Uneven Brake Wear 🟠 Medium — Owners frequently report replacing brake pads and rotors sooner than expected, sometimes under 30,000 miles. Rear brakes can wear faster than fronts, partly attributed to the Pilot Assist and Auto Hold features using them for stabilization and control.
• Sensus Infotainment System Glitches 🟡 Low — The center touchscreen (Sensus) can occasionally freeze, go blank, or become unresponsive. This often affects audio, navigation, and climate controls. A system reboot (holding the home button for ~20 seconds) often resolves the issue temporarily.
• Automatic Emergency Braking (IntelliSafe) False Activation 🟠 Medium — Some owners report the 'City Safety' or automatic braking system engaging without a clear obstacle, causing sudden and unexpected braking. Software updates from the dealer can sometimes mitigate this sensitivity. (Ref: Recalls for AEB software have been issued for some model years, check NHTSA for VIN-specific recalls.)

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used part is almost never a smart choice for control modules (ECM, CEM, VGM) on this platform. While physically interchangeable, they are 'locked' to the original vehicle's VIN and security information. The cost of 'cloning' the data from your old module to a used one by a specialist service, combined with the risk of the used part failing, often makes it a poor value proposition. Used mechanical parts like ground straps are perfectly acceptable.

What to inspect on the donor part:

• For a used control module (if attempting a clone): Match the OEM part number exactly.
• Ensure the donor vehicle was not involved in a flood or fire.
• Ask for a photo of the connector pins to check for corrosion or damage.

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

• Engine Control Module (ECM)
• Central Electronic Module (CEM)
• Vehicle Gateway Module (VGM)

Aftermarket brands forum-validated for this vehicle:

• For Batteries: Bosch, Interstate, Deka are reputable alternatives to OEM.
• For Module Cloning/Repair Services: Companies like XeMODeX specialize in Volvo electronics and are frequently mentioned in forums.

Brands owners have reported issues with on this vehicle:

• Avoid unbranded, no-name control modules from online marketplaces. They are highly likely to be incompatible or fail quickly, and cannot be properly programmed to the vehicle.

Real Owner Stories

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

Related OBD-II Codes

• P0562 — System Voltage Low — often appears alongside U0100 when a weak 12V battery or failing ground strap causes voltage drops across the CAN bus.
• U0121 — Lost Communication With Anti-Lock Brake System (ABS) Control Module — frequently triggers simultaneously with U0100 when network communication is disrupted.
• U0140 — Lost Communication With Body Control Module — another 'U' code that may appear when the Gateway Module (VGM) or power supply to the network is compromised.
• U0001 — High Speed CAN Communication Bus — related to the physical integrity of the CAN High and CAN Low wires which, if damaged, will trigger U0100.

Frequently Asked Questions