U0418 on 2021 Dodge Challenger: Invalid Brake Module Data Causes and Fixes

What's Unique About the 2021-2021 Dodge CHALLENGER

The 2021 Dodge Challenger utilizes a highly integrated Controller Area Network (CAN bus) where modules for the engine, transmission, brakes, and stability control constantly share data. A glitch or fault in one module can easily trigger a cascade of communication codes in others. It's common for U0418 to appear with a host of other 'U' codes, often pointing to a single software issue rather than multiple hardware failures, as evidenced by several FCA TSBs that list dozens of such codes to be fixed by a single PCM flash. Furthermore, FCA vehicles from this era are known to be highly sensitive to battery voltage, and a weak battery can trigger this code without any actual fault in the brake system.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• ABS warning light illuminated
• Traction Control or Electronic Stability Control (ESC/BAS) warning light on
• Check Engine Light (Malfunction Indicator Lamp - MIL) may be on
• Vehicle may feel like it's in 'limp mode' with reduced power
• Cruise control may be disabled
• Brake pedal may feel soft or have a delayed response

Most Likely Causes

1. Powertrain Control Module (PCM) Software Glitch 🔴 High Probability Multiple TSBs for FCA vehicles, including Dodge, indicate that clusters of communication codes (including U0418) can be erroneously set and are resolved by updating the PCM software. TSB 18-078-22 is a prime example for a related platform.
   How to confirm: A dealership or qualified shop with a wiTECH scan tool can check the current software calibration level against the latest available version from the manufacturer. The TSB will specify the applicable software version.
   Typical fix: Reprogramming (flashing) the PCM with the latest software. This procedure requires a stable power supply to the vehicle during the flash.
   Est. part cost: $0
2. Low Battery Voltage or Poor Connection 🔴 High Probability Modern vehicles with numerous electronic modules are sensitive to voltage fluctuations. FCA TSB 18-078-22 explicitly states that DTC U0418 can be set erroneously on related platforms if battery voltage drops below 10 volts. A weak battery can cause modules to send corrupt or incomplete data during startup.
   How to confirm: Test the battery with a digital multimeter or electronic battery tester. Voltage should be above 12.4V with the engine off and between 13.5V and 14.5V with the engine running. Check for clean, tight battery terminals.
   Typical fix: Recharge or replace the battery. Clean the battery terminals and cable ends.
   Est. part cost: $150-$350
3. Wiring Harness or Connector Issue 🟡 Medium Probability The wiring harness leading to the ABS module in the engine bay is exposed to heat, vibration, and potential moisture, which can lead to corrosion or damage over time. Water intrusion from power washing the engine bay is a possible cause of connector contamination.
   How to confirm: Visually inspect the wiring harness and connector at the ABS module for any signs of damage, chafing, or corrosion. A multimeter can be used to check for continuity and shorts in the CAN bus wires (resistance between CAN High and CAN Low should be around 60 Ω).
   Typical fix: Repair the damaged section of wiring or clean/replace the affected connector. Pigtail connectors are available for repair.
   Est. part cost: $10-$100
4. Faulty ABS Control Module ⚪ Low Probability While less common than software or wiring issues, the internal electronics of the ABS module can fail, causing it to send invalid data onto the network. This can be an internal processor fault or failure of the board itself.
   How to confirm: This is typically a process of elimination. If the software is up-to-date, the battery is healthy, and the wiring is confirmed to be good, the module itself becomes the primary suspect. An advanced scan tool may be able to communicate directly with the module and identify an internal fault.
   Typical fix: Replace the ABS control module. The new module will require programming 🎬 Watch this walkthrough on replacing the ABS module and clearing lights. and initialization to the vehicle's VIN.
   Est. part cost: $500-$1500

Rare But Worth Checking

• Faulty Wheel Speed Sensor:

Diagnosis Steps

1. Connect an advanced scan tool (e.g., wiTECH) capable of reading manufacturer-specific codes from all modules.
2. Record all present DTCs and their freeze-frame data. Note if U0418 is accompanied by other communication codes.
3. Check for any available Technical Service Bulletins (TSBs) related to the stored codes or symptoms. Pay special attention to TSBs mentioning PCM software updates for communication codes.
4. Crucial First Step: Test the vehicle's battery and charging system to ensure stable voltage. A voltage below 12.4V (engine off) or outside 13.5V-14.5V (engine running) is a red flag. TSB 18-078-22 specifically notes that U0418 can be set by a battery voltage below 10V.
5. Visually inspect the wiring harness and connectors going to the ABS module, which is typically located in the engine bay attached to the hydraulic block, on the driver's side next to the windshield washer reservoir. 🎬 See exactly where the ABS module and pump are located. Look for corrosion, moisture, pushed-out pins, or physical damage.
6. If TSBs suggest a software update, have the PCM (and/or other relevant modules) flashed to the latest version by a dealer or qualified shop.
7. If the issue persists, use the scan tool to monitor live data from the ABS module, specifically the wheel speed sensors. Check for erratic readings that could cause the ABS module to send implausible data.
8. If all other steps fail to identify the cause, the ABS module itself is the likely culprit and may require replacement and programming.

Parts You'll Likely Need

• ABS Control Module (OEM #68399772AF (replaces 68399772AG), 68258644AA) — If software and wiring are ruled out, the module's internal electronics have likely failed, causing it to send corrupt data. Note: Several part numbers may exist depending on vehicle options. 68399772AF is the control module, while 68258644AA is often listed as the actuator/pump assembly. Always verify with VIN.
  Trusted brands: Mopar
  OEM price range: $250-$700
  Aftermarket price range: $400-$900 (Remanufactured)

Related Codes That Often Appear With This One

• U0402 — Implausible Data from TCM. Often set together during a network communication event.
• U0403 — Implausible Data from Transfer Case. Often set together during a network communication event.
• U0416 — Implausible Data from ESP (Electronic Stability Program). The ESP system is integrated with the ABS module.
• U0121 — Lost Communication With Brake System Control Module. This may appear alongside U0418, indicating the problem is intermittent or progressing from invalid data to a total loss of signal.

Technical Service Bulletins (TSBs) & Recalls

• 1801122: Confirms the definition for 2021 Dodge vehicles as 'Implausible Data Received From Brake System Control Module 1'.

Platform-Specific Known Issues

• A notable TSB for other 2021 FCA vehicles (Jeep Cherokee), TSB 18-078-22, explicitly states that U0418 can be set erroneously due to a low battery condition (below 10 volts), making battery testing a critical first step.
• Another TSB for 2021 Dodge Chargers with the 3.6L engine lists U0418 among a large group of communication codes that can be fixed by a PCM software update. This strongly suggests that software is a primary suspect for this code on related platforms like the Challenger.

Mechanic-Grade Diagnostic Values

• CAN C Bus Resistance — expected: Between 53.5 Ω and 67 Ω. This is measured across the CAN High and CAN Low pins at the DLC or a module connector with the battery disconnected. A perfect reading is ~60 Ω, indicating both 120 Ω terminating resistors are present and the wiring is intact.. Failure: A reading above 67 Ω suggests an open in the CAN wiring or a missing terminating resistor. A reading below 53.5 Ω suggests a short between the CAN High and Low wires. A reading of ~120 Ω indicates one of the two terminating resistors is not being seen by the network.
• CAN Bus Voltage (Key On, Engine Off) — expected: CAN High (CAN_H) should be approximately 2.5V and CAN Low (CAN_L) should be approximately 2.5V when the bus is idle. During active communication (dominant state), CAN_H shifts to ~3.5V and CAN_L shifts to ~1.5V.. Failure: Voltages shorted to ground (0V), shorted to power (5V or 12V), or stuck at a specific level indicate a wiring fault or a faulty module pulling the bus down.
• ABS Module Power Supply Voltage (During Flash) — expected: Must be maintained between 13.2V and 13.5V.. Failure: Voltage dropping below 13.2V or climbing above 13.5V can cause the software flash to fail or corrupt the module.
• Minimum Battery Voltage for Valid Operation — expected: System voltage should not drop below 10V.. Failure: A TSB for a related platform explicitly states that U0418 can be set erroneously if battery voltage drops below 10 volts, for example during engine cranking with a weak battery.

Scan Tool Commands That Help

• wiTECH (or equivalent professional scanner): ABS Initialization — This routine is mandatory after replacing the ABS control module. It allows the vehicle's other computers to recognize and communicate with the new hardware. Failure to perform this step will result in persistent communication codes and non-functional ABS/ESC systems.
• wiTECH (or equivalent professional scanner): Restore Vehicle Configuration — After installing a new ABS module, this function copies the vehicle's specific configuration data (like tire size, options, etc.) from the Body Control Module (BCM) to the new ABS module. This ensures all systems are synchronized and prevents mismatch codes.
• wiTECH (or equivalent professional scanner): Network Test (Bus Diagnostics) — This is a high-level test used to check the integrity of the entire CAN bus network. It can help identify which modules are not communicating or if there is a general network-wide fault, which is useful when multiple 'U' codes are present.
• CDA6 (Chrysler Diagnostic Application): ECU uninitialize / Clear VIN — This is an advanced, non-dealer function used to prepare a *used* ABS module for installation in a different vehicle. It wipes the VIN and initialization status from the donor module, putting it in a 'new' state so that the recipient vehicle can program its own VIN and configuration to it.

Wiring & Ground Locations

• ABS Module / Pump Assembly — In the engine bay on the driver's side, located next to the windshield washer fluid reservoir.. This is the source of the data being flagged as invalid. The main electrical connector on this module is a primary point of failure due to potential corrosion, moisture intrusion from engine washing, or pin damage.
• ABS / Traction Control Fuses — In the main fuse box in the engine compartment. Specifically, fuses F05, F06, F36, and F39 are related to the ABS and traction control systems on this platform.. A loss of power to the ABS module due to a blown fuse will cause a loss of communication or erratic behavior, which can lead to other modules setting the U0418 code.
• CAN Bus Star Connector — Location varies, but typically found behind the instrument cluster or kick panels. It serves as a central junction point for multiple CAN bus circuits.. If an entire network is down (multiple 'U' codes), a technician can disconnect modules one by one from this connector to see if communication is restored. This helps isolate a single faulty module or wiring branch that is shorting out the entire network.

Real Owner Repair Stories

• JLwranglerforums.com user (Jeep Wrangler JL (related FCA platform)) — ABS and other warning lights, codes U0418 and U140A present.
  ❌ Tried (didn't work) Initial diagnosis was unclear due to multiple communication codes.
  ✅ What actually fixed it The root cause was a failed front passenger wheel bearing that physically shredded the wheel speed sensor wiring. Replacing the wheel bearing and the damaged wheel speed sensor resolved the codes.

OEM Part Supersession History

• 68399772AF → 68399772AG — Standard revision and update by the manufacturer.
  Heads up: The new part number (68399772AG) is the correct service replacement for the older part number.