U0140 on 2014-2020 Ram 2500: Causes and Fixes for Lost BCM Communication

What's Unique About the 2014-2020 Ram 2500

For this generation of Ram trucks, particularly model years 2014-2016, the U0140 code is uniquely and strongly tied to a known software bug. Ram issued several Technical Service Bulletins (TSBs) acknowledging that the PCM's software could falsely report a communication loss with the BCM. A key symptom noted in the TSBs and confirmed by owners in forums is that the code is 'stored' or 'permanent' and cannot be cleared with a standard scan tool until the PCM is reprogrammed with updated software by a dealer.

Diagnostic Flowchart

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

Generation note: The 2014-2020 range covers two Ram 2500 generations: the Fourth Generation (DS/DJ) from 2014-2018 and the Fifth Generation from 2019-2020. The well-documented TSBs regarding the PCM software fix specifically apply to the 2014-2016 'DS/DJ' models. While U0140 can still occur on 2019+ models, it is more likely to be caused by traditional wiring or module faults rather than the specific software bug from the earlier generation.

Symptoms You May Notice

• Check Engine Light is on
• Inability to clear the U0140 trouble code with a scan tool, often showing as 'permanent'.
• Malfunctioning interior or exterior lights
• Power windows, door locks, or remote keyless entry not working.
• Wipers behaving erratically or not working
• Various other warning lights on the dashboard (e.g., security, ABS)
• Vehicle may not start or crank in some cases.

Most Likely Causes

1. PCM Software Requires Update 🔴 High Probability Multiple TSBs were issued for 2014-2016 models to address this software bug. Key TSBs include #18-072-16 Rev A (for 5.7L), #18-002-15 Rev B (for 6.4L), and #1801315.
   How to confirm: Attempt to clear the code with a standard OBD-II scanner. If the code is listed as 'permanent' and cannot be erased, it strongly indicates the software issue. A dealer can check your vehicle's VIN against applicable TSBs.
   Typical fix: Reprogramming (flashing) the PCM with the latest software version available from Ram using the dealer's wiTECH diagnostic tool. The TSBs note the importance of maintaining stable battery voltage between 13.2 and 13.5 volts during this process.
   Est. part cost: $0
2. Wiring Harness or Connector Issue 🟡 Medium Probability The CAN bus network wiring can become damaged. A known chafe point on some Ram trucks is the wiring harness near the parking brake assembly under the dash, which can rub and short out communication wires.
   How to confirm: Visually inspect the wiring harness between the PCM and BCM, paying close attention to the area around the driver's side kick panel and parking brake. The BCM is located high up under the driver's side dashboard. Disconnect the connectors at both modules (with battery disconnected) and check for bent, loose, or corroded pins.
   Typical fix: Repairing the damaged section of wire or cleaning/replacing the faulty connector. Applying dielectric grease can help prevent future corrosion.
   Est. part cost: $10-$50
3. Poor Power or Ground to BCM ⚪ Low Probability Ram trucks are sensitive to battery voltage fluctuations. A weak battery, failing alternator, or corroded ground connection can cause voltage drops that make modules go offline. The BCM has several power fuses (e.g., F10, F12, F14, F23 in the under-hood fuse box) that should be checked.
   How to confirm: Test the battery and charging system. A healthy resting battery should be ~12.6V, and the alternator should charge at 13.7-14.7V. Check for voltage and test for ground resistance at the BCM connector using a multimeter. Ground resistance should be less than 0.1 Ω. A forum user identified a key ground point to the right of the steering column.
   Typical fix: Replacing a weak battery, fixing the charging system, or cleaning/repairing the ground connection.
   Est. part cost: $5-$300
4. Faulty Body Control Module (BCM) ⚪ Low Probability → Shop Body Control Module While less common than software or wiring issues, the BCM itself can fail internally, sometimes due to water intrusion from a leaking windshield seal dripping onto the module.
   How to confirm: This is typically diagnosed by exclusion. If the PCM software is up to date, and all wiring, power, and grounds to the BCM are confirmed to be good, the BCM itself is the likely culprit.
   Typical fix: Replacing the Body Control Module. This new module will require programming to the vehicle's specific VIN and options.
   Est. part cost: $250-$500

Rare But Worth Checking

• Faulty Aftermarket Electronics: Poorly installed remote starters, alarms, or audio equipment can tap into the CAN bus network incorrectly, causing interference and communication errors. If you have aftermarket gear, this is a potential cause.
• Faulty Totally Integrated Power Module (TIPM): → Shop Fuse Box The TIPM (the main fuse box) acts as a gateway for many circuits. While major TIPM issues were more common on pre-2013 Rams, internal failures in the 2013+ Power Distribution Center (PDC) can still disrupt communication to the BCM, causing a U0140 code.

Diagnosis Steps

1. Contact a Ram dealership with your VIN to check for applicable TSBs related to U0140. For 2014-2016 models, this is the most critical first step.
2. Attempt to clear the code with a scanner. If it's listed as 'permanent' and won't clear, a PCM software update is the most likely fix.
3. If a TSB applies, have the dealer perform the reflash. If not, proceed with diagnostics.
4. Test the battery and charging system to ensure stable voltage (~12.6V at rest, 13.7-14.7V charging).
5. Visually inspect the wiring harness and connectors between the Powertrain Control Module (PCM) and the Body Control Module (BCM). Pay special attention to the harness near the parking brake assembly for chafing.
6. Check BCM-related fuses in the under-hood fuse box (TIPM/PDC).
7. Using a multimeter, check for proper power (12V+) and ground (<0.1 Ω) at the BCM connector.
8. If equipped with the tools, perform a CAN bus network test. Check for 60 ohms of resistance across the CAN high and CAN low pins (typically pins 6 and 14 at the OBD-II port) with the battery disconnected.
9. If all wiring, power, and grounds are good and the software is up to date, suspect a faulty Body Control Module (BCM) or, more rarely, a faulty PCM.

Parts You'll Likely Need

• Powertrain Control Module (PCM) Software Update — This is not a physical part, but a software reflash is the most common, manufacturer-documented fix for the U0140 code on 2014-2016 models.
  Trusted brands: Mopar (Dealer Service)
  OEM price range: $150-$250
  Aftermarket price range: N/A
• Body Control Module (BCM) (OEM #68228904AC (for 2015 models, superseded by 68228904AH)) — If the software update does not apply or fix the issue, and the wiring is confirmed to be good, the BCM itself may have failed.
  Trusted brands: Mopar
  OEM price range: $350-$500
  Aftermarket price range: $200-$400

Related Codes That Often Appear With This One

• P0300 — TSB #18-002-15 REV B links U0140 with various misfire codes (P030X, P0300) and cylinder deactivation codes, all of which are resolved by the same PCM software update on 6.4L models.
• P3400-P3497 — These are cylinder deactivation codes. TSB #18-002-15 REV B shows that these can appear alongside U0140 due to the same PCM software glitch on 6.4L models.

Technical Service Bulletins (TSBs) & Recalls

• 18-002-15 REV B
• 18-072-16
• 1801315
• 18-002-15

Platform-Specific Known Issues

• TSB #18-072-16 Rev A: Applies to 2014 models with 5.7L engine and explicitly states the fix for a 'permanent' U0140 is a PCM software update.
• TSB #18-002-15 REV B: Applies to 2015 models with the 6.4L engine, grouping U0140 with other codes (misfire, cylinder deactivation) that are all resolved by a single PCM software update.
• TSB #18-112-15: Applies to 2014 models with 5.7L engine, also noting U0140 will be 'unsuccessful' to clear until a PCM flash is performed.
• TSB #1801315: Specifically titled 'Flash: U0140 Lost Communication With Body Control Module (BCM)', this bulletin involves reprogramming the PCM.

Mechanic-Grade Diagnostic Values

• CAN C Bus Voltage (Key On, Engine Off) — expected: CAN High (Pin 6 at OBD-II): ~2.7 Volts. CAN Low (Pin 14 at OBD-II): ~2.3 Volts.. Failure: If both lines show ~2.5V, they may be shorted together. If one line shows 0V, it may be shorted to ground.
• CAN Bus Network Resistance (Battery Disconnected) — expected: ~60 Ohms across Pin 6 and Pin 14 of the OBD-II port.. Failure: A reading of ~120 Ohms indicates one of the two terminating resistors (often in the PCM or BCM) is offline or the circuit is open. A reading of 0 Ohms or very low resistance indicates a short between the CAN High and Low wires.
• BCM Power Supply Voltage — expected: 12.2-13.0V with key off; 13.5-14.7V with engine running.. Failure: Voltage below ~9V can cause the BCM to reset and go offline.

Scan Tool Commands That Help

• wiTECH (FCA Dealer Tool): Reprogram PCM / Flash ECU — This is the specific function required to perform the software update outlined in TSBs like #18-072-16 and #18-002-15 to fix the 'permanent' U0140 code on 2014-2016 models.
• wiTECH (FCA Dealer Tool): BCM Replace / Restore Vehicle Configuration — This function is required after physically replacing the BCM. It downloads the vehicle's specific configuration data (VIN, options) from FCA servers and programs it to the new module.
• wiTECH (FCA Dealer Tool): Network Topology View — This provides a visual map of all control modules on the network, color-coding them to show which are communicating, which have DTCs, and which are offline, quickly identifying a non-responsive BCM.

Wiring & Ground Locations

• BCM Main Connectors (C1-C7) — Located high up under the driver's side dashboard, often behind the knee bolster and other panels.. These are the primary connection points for all BCM power, ground, and communication lines. Corrosion or loose pins here are a direct cause of failure. For example, on one common connector (X1), Pin 11 is an ignition voltage input and Pin 25 is a ground.
• Dash Support Grounds (e.g., G300/G301) — There are multiple ground points bolted to the metal dash support structure. One common location is to the right of the steering column. Another is to the left of a vent tube near the side of the dash support.. The BCM and other interior modules rely on these chassis grounds. A loose or corroded ground bolt here can cause intermittent communication faults and trigger a U0140. These are often described as a 'spider-looking thing' where multiple black wires come to a single bolt-down point.
• Parking Brake Harness Chafe Point — The wiring harness running near the driver's side kick panel and parking brake mechanism.. The movement of the parking brake pedal can rub through the harness insulation over time, potentially shorting the CAN bus wires contained within it and causing a loss of communication with the BCM.

Real Owner Repair Stories

• RamForum.com user (2014 Ram SLT, 50,000 miles) — A 'PERMANENT' U0140 code was found using an Actron scanner. The code could not be erased.
  ❌ Tried (didn't work) Attempting to clear the code with a consumer-grade scan tool.
  ✅ What actually fixed it The user was advised by other forum members that the issue was a known software bug documented in a TSB. The confirmed fix was to have a dealer perform a PCM software update (re-flash), which resolved the permanent code.

OEM Part Supersession History

• 68228904AB, 68228904AC, 68228904AD, 68228904AE, 68228904AF, 68228904AG → 68228904AH — Standard part revision and update process by the manufacturer.
  Heads up: The final two letters of the part number often denote minor revisions or manufacturing dates and are generally interchangeable. However, the new module must be programmed to the vehicle's VIN and specific options using a tool like wiTECH to function correctly.

Model Year Variations Within This Range

• 2014-2018 (Fourth Generation): These models are highly susceptible to the PCM software bug causing a 'permanent' U0140 code, as documented in multiple TSBs. The first diagnostic step should always be checking for this software update.
• 2019-2020 (Fifth Generation): These newer models are less likely to have the specific software bug from the previous generation. For these trucks, a U0140 code should be diagnosed with a greater focus on traditional causes like wiring, grounds, or hardware failure. The diagnostic approach is more conventional.