U0422 on 2019-2020 Ram 3500: Invalid Body Control Module Data Causes and Fixes

What's Unique About the 2019-2020 Ram 3500

On this generation of Ram HD trucks, the U0422 code is uniquely tied to the interplay between the Body Control Module (BCM), the Air Suspension Control Module (ASCM), and optional accessories like power-retractable running boards. An issue as simple as a jammed power step can cause the BCM to send a 'Signal Not Available' (SNA) message over the CAN bus network. The ASCM interprets this SNA message as invalid data, triggering a 'Service Air Suspension' warning and logging the U0422 code. This tight integration means that seemingly unrelated accessory problems can manifest as a network communication fault related to a critical system like the suspension.

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.
• Power running boards do not deploy or retract correctly, or an "obstructed" message appears.
• Air suspension may be disabled or behave erratically, sometimes getting stuck in one mode (like Aero Mode).
• Other body electronic issues may be present, such as problems with power locks, windows, or lights.
• Check Engine Light may or may not be illuminated.
• Backup camera guidance lines may disappear.

Most Likely Causes

1. Temporary Glitch After Battery Disconnect or Low Voltage 🔴 High Probability → Shop Vehicle Battery The ASCM and BCM are sensitive to voltage fluctuations. The ASCM can initialize faster than the BCM after power is restored, causing it to miss the expected data handshake and log U0422. This is a known software sensitivity.
   How to confirm: The code appears immediately after reconnecting the battery, jump-starting the vehicle, or experiencing a dead battery.
   Typical fix: Clear the DTC with an OBD-II scanner. For 2020 models built on or before July 8, 2020, a permanent fix requires a dealer to perform a software update for the ASCM per TSB #08-078-20.
   Est. part cost: $0 - $150
2. Obstructed Power Running Boards 🔴 High Probability If equipped, an obstruction (ice, mud, debris) that jams a power step causes the BCM to send a 'Signal Not Available' message, which the ASCM logs as U0422. This is documented in STAR Case #S1923000042.
   How to confirm: The code appears along with a message about the power steps being obstructed. Visually inspect the steps and their pivot points for any foreign objects.
   Typical fix: Remove the obstruction and cycle the power steps one full time (deploy and retract). The code should then move to 'stored' status and can be cleared with a scanner like wiTECH or potentially by a fuse pull.
   Est. part cost: $0
3. ASCM/BCM Software Anomaly 🟡 Medium Probability Intermittent software glitches can cause communication errors between modules. Ram has issued bulletins acknowledging these conditions are sometimes under investigation, as noted in Bulletin #9004157.
   How to confirm: The code appears intermittently without a clear cause. A dealer can check if the vehicle's modules have the latest software versions using wiTECH.
   Typical fix: A temporary reset can be performed by pulling the F50 20A ASCM fuse in the Power Distribution Center, waiting a minute, and reinstalling it. A permanent fix may require a software update from a Ram dealer.
   Est. part cost: $0 - $150
4. Wiring or Connector Issue ⚪ Low Probability
   How to confirm: Visually inspect the wiring harnesses and connectors at the BCM (located in the driver's side footwell, near the parking brake) and ASCM for any signs of corrosion, damage, or looseness. This requires a multimeter to check for continuity and shorts.
   Typical fix: Repair or replace the damaged section of the wiring harness or clean the affected connectors. Water intrusion from a leaking windshield is a known potential cause of BCM connector corrosion.
   Est. part cost: $10-$100
5. Failing Body Control Module (BCM) ⚪ Low Probability → Shop Body Control Module
   How to confirm: This is a diagnosis of exclusion. If all wiring, software, and other potential causes have been ruled out, the BCM itself may be failing internally. This requires advanced diagnostics with a high-end scan tool to monitor data streams.
   Typical fix: Replace the Body Control Module. The new module will require programming to the vehicle's specific VIN and configuration by a dealer or a specialized shop.
   Est. part cost: $400-$600

Diagnosis Steps

1. Check if the vehicle is equipped with power running boards. If so, inspect them for any obstructions like mud, ice, or debris. Clear any blockages and cycle the steps.
2. If the code appeared after a battery replacement or jump-start, attempt to clear the code using an OBD-II scanner. If it returns, check for TSB #08-078-20 applicability.
3. Perform a hard reset. As a temporary fix, locate the Power Distribution Center and remove the F50 20A fuse for the ASCM. 🎬 See this walkthrough on replacing the air suspension fuse. Wait 60 seconds, then reinstall it. This is a common fix reported by owners. Also check that all fuses in the box are fully seated.
🎬 Watch: Troubleshooting air suspension issues after a battery disconnect.
4. Connect a capable scan tool (like AlfaOBD or the dealer's wiTECH) to see which module is logging the U0422 code (it is almost always the ASCM on these trucks) and to check for other stored codes.
5. Check for any available Technical Service Bulletins (TSBs) related to the BCM or ASCM. A dealer may need to perform a software update, especially TSB #08-078-20 for the battery disconnect issue.
6. Visually inspect the wiring harness and connectors for the BCM (driver's side footwell) and ASCM. Look for any signs of water intrusion, corrosion, or physical damage.
7. If all other steps fail, the issue may be an internal fault in the Body Control Module, which would require professional diagnosis and replacement.

Parts You'll Likely Need

• Body Control Module (BCM) (OEM #68372337AD / 68372337AF) — This is the source of the invalid data. It is only replaced as a last resort after all other causes (software, wiring, temporary glitches) have been ruled out. Part numbers are often superseded; AF is a later revision of AD.
  Trusted brands: Mopar
  OEM price range: $400-$600
  Aftermarket price range: $250-$450

Related Codes That Often Appear With This One

• U0132 — Lost Communication With Suspension Control Module Level Control. This can appear alongside U0422 during a network disruption. A user on the HD Rams forum resolved this by pulling the F50 fuse.
• U0421 — Invalid Data Received From Suspension Control Module. This can also be set during the same fault event that triggers U0422. [Bulletin #9004157]

Technical Service Bulletins (TSBs) & Recalls

• Bulletin #9004157: Mentions U0422 in the context of an intermittent condition under investigation, and suggests a fuse pull for the ASCM as a diagnostic reset.
• STAR Case #S1923000042 / TSB #08-078-20: Documents that U0422 can be set by obstructed power side steps or after a battery reconnection, and that a software update is available for the latter.
• TSB #08-078-20: Specifically addresses U0422-00 setting in the ASCM after a battery disconnect on 2020 Ram 1500 models (and by extension, HD models with the same architecture) built on or before July 8, 2020. The fix is to reprogram the ASCM.

Platform-Specific Known Issues

• A known issue involves the power running boards getting obstructed, which causes the BCM to send a signal that the Air Suspension Control Module interprets as invalid, triggering code U0422 and a 'Service Air Suspension' message. This is detailed in STAR Case #S1923000042.
• A glitch following a battery disconnect can also cause the ASCM to set this code; a software update under TSB #08-078-20 was released for 2020 models to address this specific condition.

Mechanic-Grade Diagnostic Values

• CAN Bus Network Resistance — expected: ~60 Ohms (measured between Pin 6 and Pin 14 of the OBD-II port with battery disconnected). Failure: A reading of ~120 Ohms indicates an open circuit or a missing terminating resistor in one of the modules. A reading near 0 Ohms indicates a short between the CAN High and CAN Low wires.
• CAN Bus Voltage (Key On, Engine Off) — expected: CAN High (Pin 6): ~2.5V to ~3.5V. CAN Low (Pin 14): ~2.5V to ~1.5V.. Failure: Voltages that are stuck high, low, or at 0V indicate a short to power, ground, or an open circuit.

Hidden / Shadow Codes Worth Checking

• U0422-00: This is the most common format for this DTC, where '-00' indicates a generic or non-specific fault type. TSB #08-078-20 specifically calls out 'U0422-00' as the code set in the ASCM after a battery disconnect, confirming this is the expected variant for that issue. (see via A capable scan tool like wiTECH or AlfaOBD that can read manufacturer-specific codes from individual modules like the ASCM.)

Scan Tool Commands That Help

• AlfaOBD: Backup vehicle configuration to a file — This function should be used *before* removing the original BCM. It saves all the vehicle-specific settings, which can then be restored to the new module.
• AlfaOBD: Restore vehicle configuration from file — This is used to program a new or used BCM with the settings saved from the original module. This is a critical step after physical replacement.
• AlfaOBD: Hood Open Vehicle Configuration Program Status — A user reported that after a BCM swap and configuration restore, an airbag light remained and the radio was inoperative. Running this specific procedure resolved the lingering communication issues with other modules.
• wiTECH: Reprogram the ASCM — This is the dealer-level function required to apply software updates, such as the one specified in TSB 08-073-20 to fix communication loss codes.

Wiring & Ground Locations

• Body Control Module (BCM) — Located high in the driver's side footwell, up behind the dash assembly, often near the parking brake mechanism. It is held in by four 10mm nuts and has multiple large connectors.. This is the source of the 'invalid data'. Its location makes it susceptible to water intrusion from a leaking windshield, and its connectors can be difficult to access and fully seat, potentially causing poor connections.
• Air Suspension Control Module (ASCM) — Underneath the driver's seat, protected by a black plastic cover that clips on.. This is the module that most commonly logs the U0422 code on Ram trucks with air suspension. Checking its connections is a valid diagnostic step, especially if the F50 fuse pull doesn't resolve the issue.
• Chassis Ground — A key ground connection point is located on the sheet metal below the driver's side battery.. Corrosion at this main ground point can cause high resistance, leading to unstable voltage supply for multiple modules, including the BCM, which can cause communication codes like U0422.

Real Owner Repair Stories

• User report on RamForum.com (2014 Ram 1500 (applicable process for 5th Gen)) — Airbag light and non-functional radio after swapping in a donor BCM.
  ❌ Tried (didn't work) Swapping the BCM., Using AlfaOBD to restore the vehicle configuration from the original BCM to the donor BCM.
  ✅ What actually fixed it After restoring the configuration, the user had to run a specific AlfaOBD procedure called 'Hood Open Vehicle Configuration Program Status'. Executing this command successfully cleared the airbag code and restored radio function, completing the BCM swap process.

Model Year Variations Within This Range

• 2020: 2020 models built on or before June 18, 2020, may have ASCM software that is susceptible to setting codes like U0132 after a MIL is illuminated. TSB 08-073-20 involves a software update to correct this.
• 2020: 2020 models built on or before July 8, 2020, are specifically called out in TSB #08-078-20 for setting U0422 in the ASCM after a battery disconnect. The fix is to reprogram the ASCM with updated software.