U0073 on 2008-2014 Scion xD: CAN Bus Communication Failure Causes and Fixes

What's Unique About the 2008-2014 Scion xD

The Scion xD is built on Toyota's B platform, sharing its core electronics with vehicles like the Yaris and Prius c. On these platforms, the U0073 code doesn't usually point to one single, universal failure. However, forum discussions and technical documents strongly suggest that the ABS (Anti-lock Brake) and Skid Control ECU, also known as the Brake Actuator Assembly, is a critical node on the CAN bus. A failure in this module or its wiring is a common reason for the entire network to go down, often triggering a cascade of warning lights including ABS, VSC, and the main Brake light.

Symptoms You May Notice

• Multiple warning lights on the dashboard at once (Check Engine, ABS, VSC, Power Steering, Brake)
• Vehicle may not start or may stall unexpectedly.
• Speedometer, tachometer, or other gauges may stop working or behave erratically
• Loss of power features like power locks or air conditioning
• Transmission may be stuck in one gear (limp mode)
• Brakes may feel different or require more effort.

Most Likely Causes

1. CAN Bus Wiring Fault 🔴 High Probability Wiring can become damaged from vibration, heat, or chafing on chassis components. Rodents are also known to chew on harnesses. Connectors can corrode from water intrusion, or become contaminated with fluids like oil, disrupting the signal.
   How to confirm: A technician will perform a visual inspection of harnesses, especially around the ABS module, fuse box, and firewall. They will check for continuity and test for shorts between the CAN High and CAN Low wires, or shorts to power/ground.
   Typical fix: Repairing the specific section of damaged wire, or cleaning/replacing a corroded connector.
   Est. part cost: $5-$50
2. Poor Battery Voltage or Ground Connection 🟡 Medium Probability → Shop Vehicle Battery All electronic modules require a stable power source. A weak battery, failing alternator, or corroded ground strap can cause voltage drops that make modules malfunction and disrupt the network. There are documented cases where low battery voltage (~9V) caused a U0073 that was misdiagnosed by a dealer as a faulty ABS module.
   How to confirm: Test the battery voltage at rest (should be >12.4V) and while the engine is running (should be 13.5-14.5V). Inspect and clean the main battery terminals and chassis ground points.
   Typical fix: Charging or replacing the battery, replacing the alternator, or cleaning/repairing ground connections.
   Est. part cost: $10-$400
3. Faulty ABS / Skid Control ECU (Brake Actuator Assembly) 🟡 Medium Probability This module is a central hub for the CAN network. An internal failure can cause it to stop communicating or flood the network with bad data, bringing the entire bus down.
   How to confirm: Using a professional scan tool to see if all other modules are reporting a loss of communication with the ABS module (often code U0129). A technician may disconnect the module and see if communication between other modules is restored.
   Typical fix: Replacement of the ABS Actuator and Pump Assembly, which often requires programming or calibration to the vehicle.
   Est. part cost: $400-$1200
4. Faulty Aftermarket Electronics ⚪ Low Probability Improperly installed aftermarket stereos, remote starters, alarms, or even plug-in insurance/telematics devices (e.g., Progressive Snapshot) can interfere with or disrupt CAN bus signals.
   How to confirm: Temporarily disconnect any and all aftermarket electronic devices, especially those plugged into the OBD-II port, to see if the U0073 code disappears and normal operation resumes.
   Typical fix: Correctly reinstalling or permanently removing the faulty aftermarket device.
   Est. part cost: $0

Rare But Worth Checking

• Failed ECM (Engine Control Module) or other module: While the ABS module is a more common culprit on this platform, any module on the CAN bus can theoretically fail and cause this code. Diagnosis involves systematically checking which module is offline. A burnt electronic smell near a specific module can sometimes indicate its failure.

Diagnosis Steps

1. Check Battery and Charging System: Before any complex diagnosis, ensure the battery has at least 12.4 volts at rest and that the alternator is charging correctly (13.5-14.5V) when the engine is running. Clean any corrosion from terminals and check main ground connections.
2. Disconnect Aftermarket Devices: Unplug any aftermarket devices, especially those connected to the OBD-II port like insurance trackers or third-party tuners. Clear codes and see if the problem returns.
3. Scan for All Codes: Use a professional scan tool to perform a full network scan. Note all 'U' codes and which modules are reporting 'no communication'. This can help pinpoint the origin of the failure.
4. Visual Inspection: Thoroughly inspect visible wiring harnesses for signs of damage, chafing, rodent activity, or corrosion, paying close attention to the wiring near the ABS module and the main fuse box.
5. Check CAN Bus Resistance: With the battery disconnected, measure the resistance between pins 6 (CAN-H) and 14 (CAN-L) on the OBD-II port. A healthy network should read approximately 60 Ohms. A reading of 120 Ohms indicates an open in the bus or a problem with one of the two terminating resistors.
6. Isolate Modules: If resistance is incorrect or the network is still down, a technician will begin disconnecting modules one by one (starting with the most likely culprits like the ABS module) and re-testing the network until communication is restored.
7. Use Advanced Diagnostics: A technician may use a tool like Toyota's Techstream to run a 'CAN Bus Check', which provides a real-time, color-coded status of all modules on the network, helping to quickly identify the non-communicating component.

Parts You'll Likely Need

• ABS Actuator and Pump Assembly (OEM #44050-52800, 44050-52G60, 44050-52G61, 44050-52820, 44510-52700) — This module is a common point of failure on the CAN bus for this platform. An internal fault can take the entire network offline.
  Trusted brands: Toyota (OEM), Aisin
  OEM price range: $800-$1500
  Aftermarket price range: $400-$800 (Remanufactured)
• Battery — A weak or failing battery can cause low voltage conditions that disrupt module communication, mimicking a more severe network fault.
  Trusted brands: Toyota TrueStart, Interstate, DieHard
  OEM price range: $150-$250
  Aftermarket price range: $100-$200
• Wiring Repair Supplies — If the issue is a broken or corroded wire, the fix involves repairing the harness rather than replacing a major component.
  OEM price range: $5-$50
  Aftermarket price range: $5-$50

Related Codes That Often Appear With This One

• U0100 — Lost Communication with ECM/PCM. This code is often logged by other modules when the U0073 fault is active, as they can no longer hear the engine computer.
• U0129 — Lost Communication With Brake System Control Module. This code specifically points to a communication problem with the ABS/VSC module, which is a common cause for U0073 on this vehicle.

Technical Service Bulletins (TSBs) & Recalls

• No specific Technical Service Bulletins (TSBs) directly addressing the U0073 code on the 2008-2014 Scion xD were found during research. Diagnosis relies on general Toyota CAN bus troubleshooting procedures.

Platform-Specific Known Issues

• The connector at the ABS Actuator Assembly is a key inspection point. Due to its location in the engine bay, it can be susceptible to moisture and corrosion over time, which can lead to intermittent or total loss of communication from this critical module.

Mechanic-Grade Diagnostic Values

• CAN Bus Network Resistance — expected: ~60 Ohms. Failure: A reading of ~120 Ohms indicates an open circuit or one missing terminating resistor. A reading significantly less than 60 Ohms suggests a short circuit between the CAN lines.
• CAN Bus Voltage (CAN-H to Ground) — expected: ~2.5V to 3.5V (average ~2.6V on a multimeter). Failure: Voltage that is stuck high, stuck low, or absent indicates a fault on the CAN High line.
• CAN Bus Voltage (CAN-L to Ground) — expected: ~1.5V to 2.5V (average ~2.4V on a multimeter). Failure: Voltage that is stuck high, stuck low, or absent indicates a fault on the CAN Low line.
• Terminating Resistor Check — expected: ~120 Ohms. Failure: If disconnecting a suspected terminating module (like the ECM or Combination Meter) does not change the bus resistance from 60 Ohms to 120 Ohms, that module likely does not contain the resistor. If the reading is already 120 Ohms, disconnecting the correct module should cause an open circuit reading.

Hidden / Shadow Codes Worth Checking

• U0073/94: This is an example of a detail code that may accompany the main U0073 code, providing more specific information about the nature of the 'Bus Off' state. (see via These manufacturer-specific detail codes are typically only visible using advanced diagnostic tools like Toyota's Techstream software.)

Scan Tool Commands That Help

• Toyota Techstream: CAN Bus Check — This function is invaluable for a U0073 code. It polls all ECUs on the network and displays a graphical layout showing which modules are communicating and which are not, quickly pointing the technician to the source of the communication breakdown.
• Toyota Techstream: Data List (for VSC/ABS) — Allows for monitoring live data from sensors and checking for momentary interruptions in the harness or connectors that could cause intermittent communication loss.

Wiring & Ground Locations

• A1, A2 — Left side of the engine compartment, part of the engine room junction block and relay block area.. These are primary ground points for components in the engine bay. A loose or corroded connection here can affect multiple systems, including the ABS module or ECM.
• B1 — Left front of the engine compartment.. Another critical engine bay ground point. Its integrity is essential for stable voltage to nearby ECUs.
• C2 — Top center of the engine.. Provides a ground path for engine-mounted sensors and components. A fault here could introduce electrical noise or unstable operation.
• ECM Location — Right rear of the engine compartment.. The ECM contains one of the two 120-Ohm CAN terminating resistors. The wiring and connector integrity at the ECM are critical for network health.

Real Owner Repair Stories

• Reddit user in r/Toyota (2019 Toyota (similar platform)) — ABS/VSC/TRC lights on, sluggish performance. Codes U0073, U0100, U0129 present.
  ❌ Tried (didn't work) Took to a dealership, who first suggested replacing ABS wheel speed sensors, then recommended replacing the entire expensive ABS module.
  ✅ What actually fixed it The owner used a Carista scanner to view live data and noticed the ignition voltage was only 9V. They replaced the weak battery, and all warning lights and codes disappeared.
• YouTube channel 'Car Hospital' (2007 Toyota Camry (similar CAN architecture)) — RPM and speedometer flickering, ABS and brake lights on, code U0073 stored.
  ❌ Tried (didn't work) Checking the full ABS wiring harness.
  ✅ What actually fixed it The technician removed the ABS control module from the hydraulic block, opened the electronic unit, and identified a failed capacitor on the circuit board. Replacing just the capacitor restored function and cleared the code.

"I Checked Everything" — The Actual Cause

• In the context of this electronic code, the equivalent of a 'smoke test clean' scenario is when all wiring resistance and continuity checks appear normal. A documented case showed that even with wiring integrity confirmed, the root cause was a weak battery providing only 9 volts, causing modules to randomly drop off the network. This was missed by a professional dealership diagnosis that immediately pointed to a faulty ABS module.

When the Usual Fixes Don't Work

• While the ABS module is a very common cause for U0073 on this platform, it should not be the default diagnosis. A well-documented case shows that a dealership incorrectly condemned the ABS module when the true fault was a weak battery causing low system voltage. The owner saved over a thousand dollars by checking the battery voltage with a simple scanner and replacing it, which completely resolved the U0073 and all related codes. This proves that basic electrical health checks must be performed before assuming the most expensive component has failed.

OEM Part Supersession History

• 44050-52800 → 44050-52821 — Standard part revision and update by the manufacturer.
  Heads up: Part number 44050-52800 is specifically for 2008-2009 models WITHOUT Vehicle Stability Control (VSC). Using it on a VSC-equipped car will not work. It is critical to match the part number to the vehicle's VIN to ensure compatibility.

Model Year Variations Within This Range

• 2008-2014: The most significant variation affecting this repair is the presence of optional Vehicle Stability Control (VSC). Base models may not have VSC and use a different ABS Actuator Assembly than models equipped with VSC. The part numbers are different, and the units are not interchangeable.

Diagnostic Flowchart

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For the ABS Actuator Assembly, which can cost over $1000 new from the dealer, a used part from a reputable automotive recycler is a very practical and cost-effective choice.

Donor-vehicle mileage cap: roughly under 100000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• Verify the part number EXACTLY matches your original unit, paying close attention to with/without VSC compatibility.
• Obtain the VIN from the donor vehicle to cross-reference its options.
• Inspect the electrical connector and pins on the used module for any signs of corrosion, moisture, or physical damage.
• Ask about the recycler's warranty and return policy in case the unit is also faulty.

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

• ABS Actuator Assembly. While a used OEM unit is acceptable, avoid no-name aftermarket clones. Stick to original Toyota/Aisin parts (new, used, or professionally remanufactured).

Aftermarket brands forum-validated for this vehicle:

• Aisin (The original equipment manufacturer for Toyota)

Brands owners have reported issues with on this vehicle:

• Unbranded, low-cost ABS modules from online marketplaces should be avoided due to the complexity and safety-critical nature of this component.

Real Owner Stories

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

Related OBD-II Codes

• U0129 — Lost Communication With Brake System Control Module. This code is often set in other modules on the network when the ABS module, a common culprit, fails and stops communicating, causing the primary U0073 fault.
• P0562 — System Voltage Low. This code may appear alongside U0073 if the root cause is a weak battery or failing alternator, as the low voltage condition disrupts communication for all modules on the CAN bus.
• U0100 — Lost Communication With ECM/PCM. Frequently appears with U0073 because a general bus failure means no modules can talk to each other, including the main Engine Control Module.
• C1241 — Low or High Power Supply Voltage (ABS/VSC Code). This code can indicate a power supply issue internal to the ABS module itself. This internal fault can be the precursor to the module failing entirely and bringing down the CAN bus, triggering the U0073.

Frequently Asked Questions