U0422 on 2019-2020 Ram 2500: Invalid BCM Data Causes and Fixes

What's Unique About the 2019-2020 Ram 2500

On this generation of Ram Heavy Duty trucks, U0422 is very commonly associated with the optional Active-Level™ Air Suspension. The Air Suspension Control Module (ASCM) is sensitive and may log this code due to temporary events like a battery disconnect or even if the optional power running boards are obstructed. Ram has issued technical service bulletins (TSBs) acknowledging these software sensitivities, often recommending a simple fuse reset or a software update as the first line of defense before attempting more complex repairs. A user on HDRams.com confirmed that pulling the F50 ASCM fuse 🎬 Watch: How to reset your air suspension and check fuses cleared the active code, which then allowed the dealer to perform the TSB flash update.

Diagnostic Flowchart

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

Symptoms You May Notice

• "Service Air Suspension System" message on the instrument cluster.
• Air suspension may be inoperable or stuck at one height.
• Power running boards may not operate correctly or display an "obstruction" message.
• Erratic behavior of interior/exterior lights, power windows, or door locks.
• Check Engine Light or other warning lights may be illuminated.
• In some cases, the truck may enter a 'limp mode' with reduced functionality.
• Incorrect outside temperature reading (e.g., -40 degrees).
• Loss of backup camera guidance lines or inability to switch camera views.

Most Likely Causes

1. Temporary Glitch After Battery Disconnect or Low Voltage 🔴 High Probability → Shop Vehicle Battery The Air Suspension Control Module (ASCM) can initialize at a different speed than the BCM after a power interruption, causing it to miss an expected communication handshake and log a fault. This is a known software sensitivity confirmed by FCA documentation.
   How to confirm: The code appears immediately after a battery replacement, jump-start, or dead battery event. Check battery voltage; a reading below 12.4V at rest indicates a weak battery. The BCM may log a specific low-voltage code if its power supply drops below 9.0 volts.
   Typical fix: First, try clearing the code with a scan tool. If it persists, perform a hard reset by pulling the F50 20A ASCM fuse in the Power Distribution Center for a few minutes, then reinstalling it. This fix was confirmed by multiple owners on HDRams.com. If the code returns, a software update per TSB #08-078-20 may be required for 2020 models.
   Est. part cost: $0
2. Obstructed Power Running Boards 🟡 Medium Probability If equipped, when the power running boards are obstructed by ice, mud, or an object, the BCM sends a 'Signal Not Available' (SNA) message that the ASCM interprets as invalid data, triggering U0422-00. The hinge pins are also known to corrode and seize, which can cause the motor to strain and the module to report an error.
   How to confirm: The 'Service Air Suspension' message appears simultaneously with the 'Power Side Steps Obstructed' message. Check for and clear any obstructions. Cycle the boards by opening and closing the door.
   Typical fix: Clear the obstruction and cycle the power running boards. The code should move to 'stored' status and can then be cleared with a scan tool like wiTECH. In cases of corrosion, the hinge pins may need to be pressed out, cleaned, and lubricated. 🎬 See how to rebuild and unjam seized power running boards
   Est. part cost: $0
3. Air Suspension Control Module (ASCM) Software Issue 🟡 Medium Probability Ram has released several software updates to address communication glitches. TSB 08-078-20 specifically addresses U0422 appearing after a battery disconnect on 2020 models. Other TSBs also address communication loss and erroneous messages that can be resolved with a flash.
   How to confirm: A dealership or a shop with a capable scan tool (like wiTECH) can check the current software calibration of the ASCM and compare it against the latest available version per TSBs.
   Typical fix: Reprogramming the ASCM with the latest software version. This must be done by a dealer or a properly equipped independent shop. The labor cost for flashing a module is typically around one hour of labor, ranging from $150 to $300.
   Est. part cost: $0 (if covered by warranty/recall), $150-$300 (labor for flashing)
4. Failing Body Control Module (BCM) ⚪ Low Probability → Shop Body Control Module Water intrusion from a leaking windshield, cracked rear window frame, or leaking third brake light (CHMSL) can drip onto the BCM or its connectors, causing corrosion and internal faults. This is a known issue, with owners reporting catastrophic electrical problems after windshield tinting jobs due to water runoff onto the BCM.
   How to confirm: Multiple, seemingly unrelated electronic systems are malfunctioning (e.g., lights, locks, radio, A/C all at once). A diagnostic scan shows numerous communication codes pointing to the BCM. A technician will test power, ground, and network circuits at the BCM, which is located under the driver's side dashboard.
   Typical fix: Replacement of the Body Control Module. The new module must be programmed to the vehicle's specific VIN and configuration; the truck will not start until this is done.
   Est. part cost: $300-$600

Rare But Worth Checking

• CAN Bus Wiring Fault: The Controller Area Network (CAN) is the vehicle's communication backbone. A chafed, corroded, or shorted wire between the BCM and ASCM can corrupt messages, causing this code. This is rare but can occur after accidents, rodent damage, or previous improper repairs.
• Improperly Installed Aftermarket Accessories: Aftermarket electronics like remote starters, alarms, LED lighting decoders, or trailer brake controllers can interfere with the CAN bus network if not installed correctly. There are owner reports of widespread electrical issues, including U0422, that were resolved by unplugging a faulty aftermarket trailer brake controller.

Diagnosis Steps

1. Check Battery Health: Ensure the battery voltage is above 12.4V with the engine off. Charge or replace the battery if necessary. Low or unstable voltage is a primary cause of network codes. The BCM requires a stable voltage between 9.0 and 16.0 volts to function correctly.
2. Scan All Modules: Use a high-quality OBD-II scanner that can read codes from all vehicle modules (ASCM, BCM, PCM, etc.). Note which module is specifically logging the U0422 code. For this generation, you may need a security gateway bypass cable (like a Chrysler 12+8 cable) 🎬 Watch: How to install a security gateway bypass for diagnostics to gain full diagnostic access.
3. Check for TSBs: Check for any open recalls or Technical Service Bulletins (TSBs). TSB #08-078-20 (for 2020 models) and TSB #9004157 are highly relevant.
4. Perform Fuse Reset: As a first, simple step, remove the F50 20A ASCM fuse from the under-hood Power Distribution Center for 60 seconds, then reinstall it. Many owners have reported this clears the fault. Also check that all fuses in the panel are fully seated, as loose fuses have been found to be a cause.
5. Inspect for Obvious Causes: Check for obstructions under power running boards (if equipped). Visually inspect the BCM (under driver's dash) and its connectors for any signs of water intrusion or corrosion, especially after a windshield replacement or tint job.
6. Advanced Diagnostics (CAN Bus Check): With the battery disconnected, measure the resistance between Pin 6 (CAN High) and Pin 14 (CAN Low) at the OBD-II port. A healthy CAN C bus should read approximately 60 ohms. A reading of 120 ohms indicates a missing terminating resistor in a key module (like the PCM or TIPM). With the ignition on, voltage should be ~2.7V for CAN High and ~2.3V for CAN Low.
7. Module Verification: If wiring is confirmed to be good, the final step is to determine if the BCM itself is faulty. This is typically a process of elimination and may involve flashing the module with updated software before condemning it.

Parts You'll Likely Need

• Body Control Module (BCM) (OEM #68406223AF (example, VIN specific)) — If software updates and wiring checks fail, the BCM itself may have an internal fault causing it to send corrupt data. Replacement requires professional programming. Note: The searched part number is an example and may not be correct for all vehicles; always verify with VIN.
  Trusted brands: Mopar
  OEM price range: $400-$600
  Aftermarket price range: $250-$450

Related Codes That Often Appear With This One

• U0132 — This code means 'Lost Communication with Air Suspension Control Module'. It can appear alongside U0422, indicating a broader communication breakdown on the network involving the air suspension system. TSB #9004157 and TSB 08-175-21 list this as a related code.
• U0421 — This code means 'Invalid Data Received from Suspension Control Module'. The TSB #9004157 mentions it appearing with U0422, suggesting a two-way communication problem between the BCM and ASCM.
• C15E1-97 — 'Left Rear Air Spring Intake - Component or System Operation Obstructed or Blocked'. This code is also mentioned in TSB 08-175-21, indicating the software update addresses physical operation faults as well as communication errors.

Technical Service Bulletins (TSBs) & Recalls

• 9004157: Addresses U0422, U0132, and U0421 on 2019 models, recommending a fuse pull to clear temporary faults.
• 08-175-21: Supersedes TSB 08-073-20. Involves reprogramming the ASCM with updated software to address a host of DTCs and symptoms like 'Service Air Suspension' light, inoperable system, and communication codes on 2019-2022 models.
• S1923000001: Incomplete TSB number from pass 1. No further valid information found.

Platform-Specific Known Issues

• A known software issue can cause U0422 to set in the Air Suspension Control Module (ASCM) after the battery has been disconnected.
• TSB #9004157 specifically addresses U0422 on 2019 models, noting the condition was under investigation and that a simple fuse pull could resolve temporary occurrences.
• TSB #08-175-21, which supersedes a 2020 TSB, provides a software update for the ASCM on 2019-2022 models to fix various communication and operational faults, including symptoms that can trigger U0422.
• Water leaks from the rear sliding window frame or the Center High-Mounted Stop Lamp (CHMSL) are known issues on these trucks and can lead to water damage to modules located in the cab.

Mechanic-Grade Diagnostic Values

• CAN Bus Network Resistance — expected: ~60 Ohms. Failure: A reading of ~120 Ohms indicates a terminating module is offline or its resistor has failed. A reading near 0 Ohms indicates a short between the CAN High and Low wires.
• CAN High Voltage (Key On, Engine Off) — expected: ~2.7 Volts. Failure: Significant deviation, or a reading of ~2.5V if shorted to CAN Low.
• CAN Low Voltage (Key On, Engine Off) — expected: ~2.3 Volts. Failure: Significant deviation, or a reading of ~2.5V if shorted to CAN High.
• BCM Operating Voltage — expected: 10.0 to 16.0 Volts. Failure: A BCM-specific DTC (B2199-16) can be set if voltage on its main power circuits drops below 9.0 volts for more than a second, which can lead to invalid data transmission.

Hidden / Shadow Codes Worth Checking

• U0422-00: The '-00' is a Failure Type Byte (FTB) that can be seen with advanced scan tools like wiTECH. It provides more specific information but does not fundamentally change the meaning of the code. In this case, it's often seen when the BCM sends a 'Signal Not Available' status for the power running boards. (see via OEM-level scan tools like wiTECH or high-end aftermarket scanners.)

Scan Tool Commands That Help

• wiTECH 2.0: Flashes Tab / Reflash Module — Used to check for and apply available software updates to the ASCM or BCM, which can resolve known communication glitches per TSBs. A stable power supply (13.2-13.5V) is required during the flash.
• wiTECH 2.0: Restore Vehicle Configuration — This function is mandatory after replacing the Body Control Module. It downloads the vehicle's specific configuration from FCA servers and programs it to the new BCM. The vehicle will not operate correctly until this is performed.
• AlfaOBD (Aftermarket): Backup vehicle configuration to a file / Restore vehicle configuration — For advanced DIYers, this allows saving the current BCM configuration before removal and restoring it to the new module, potentially avoiding a trip to the dealer for programming.

Wiring & Ground Locations

• CAN Bus Star Connector (Hub) — Located under the dashboard, often near the steering column or behind the passenger side kick panel. It is a multi-position connector (often green) where many CAN bus wires converge.. This is a central junction for the CAN network. A poor connection or corrosion in this single connector can disrupt communication between multiple modules, including the BCM and ASCM, causing network-wide faults.
• Security Gateway Module (SGW) — Located directly behind the instrument cluster.. On this platform, the SGW prevents direct write access (like clearing codes or running bidirectional tests) from the OBD-II port. A 12+8 bypass cable must be connected directly to the SGW and its harness to allow a scan tool full diagnostic control.
• BCM Power and Ground Circuits — At the BCM connectors under the driver's side dash.. Specific circuits to test are the fused B+ inputs (circuits A903 and A904) and the main ground circuits (e.g., Z906). High resistance on these power or ground paths can cause the BCM to malfunction and send invalid data.

Real Owner Repair Stories

• Ram Heavy Duty Forum user (Ram Heavy Duty with Air Suspension) — 'Service Air Suspension' message appeared and would not clear.
  ❌ Tried (didn't work) Restarting the truck multiple times.
  ✅ What actually fixed it The owner inspected the under-hood fuse box and found several fuses were not fully seated. Firmly pushing in all fuses, specifically mentioning those related to the air suspension (05, 50, 87), resolved the issue and the message disappeared.
• 5thGenRams Forum user (2019 Ram 1500 (120k miles)) — After a windshield tint job, headlights and taillights strobed, multiple warning lights appeared, park sensors alarmed, and turn signals failed. Wiggling BCM wires made symptoms worse.
  ❌ Tried (didn't work) Disconnecting/reconnecting battery., Air drying the BCM area with a fan overnight., Dealer replacing the battery for $460, which did not fix the issue.
  ✅ What actually fixed it The story strongly implies the root cause was water intrusion into the Body Control Module (BCM) from the tinting procedure, a known vulnerability. The final repair was not posted, but the diagnostic path clearly pointed to a water-damaged BCM that the dealer was initially misdiagnosing.
• RamForum.com user (Ram Truck) — A host of electrical issues and communication codes.
  ❌ Tried (didn't work) Diagnosing individual modules.
  ✅ What actually fixed it The issue was traced to a faulty aftermarket trailer brake controller that was disrupting the CAN bus network. Unplugging the aftermarket controller resolved all symptoms.

"I Checked Everything" — The Actual Cause

• A complex 'Invalid Data' code (U0422) accompanied by a 'Service Air Suspension' message was traced back to a simple mechanical issue. Instead of a failed module or wiring short, the cause was several fuses in the main fuse box that had worked themselves loose. Standard electronic tests would not have found this; a physical inspection and push on all fuses resolved the problem.

When the Usual Fixes Don't Work

• While a software glitch or temporary power loss is a very common cause, do not assume it's always a simple reset. In one documented case, a 2019 Ram 1500 owner experienced a cascade of electrical failures after a windshield tinting. The dealer insisted the battery was bad, but replacing it did nothing to solve the problem. The symptoms pointed directly to a water-damaged BCM, a fix far more involved than a simple fuse pull or software flash. This highlights the need to consider the physical environment and recent service history of the truck, as water intrusion can create identical symptoms but requires a much more complex repair.

Model Year Variations Within This Range

• 2019+: Full diagnostic access (clearing codes, bidirectional controls) requires bypassing the Security Gateway Module (SGW) located behind the instrument cluster. An adapter, commonly a 'Chrysler 12+8 Cable', is needed to connect a scan tool directly to the CAN bus wiring before and after the SGW.
• 2019 vs. 2018: BCM connector pinouts can change even on the same generation truck. For example, when adding OEM bed lights, the cargo lamp driver circuit on a 2018 model was on BCM connector C1, pin 5. For the 2019 model, that same function moved to connector C3, pin 17. This confirms that wiring diagrams specific to the exact model year are critical.