U0100 on 2014-2015 Ram 2500: Lost Communication with ECM/PCM Causes and Fixes

What's Unique About the 2014-2015 Ram 2500

For this specific generation of Ram 2500 with the 6.7L Cummins engine, a U0100 code is famously linked to a software issue. Ram issued a Technical Service Bulletin (TSB #18-037-16 REV. A) acknowledging that a software glitch could cause a "No crank/No start issue" accompanied by the U0100 code. This makes a dealer-level software update a primary and unique fix for these trucks, distinguishing it from the purely hardware-related faults that cause this code on other vehicles.

Diagnostic Flowchart

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

Symptoms You May Notice

• No-crank, no-start condition.
• Engine stalls intermittently while driving.
• Check Engine Light is on.
• Multiple other warning lights may illuminate on the dashboard (e.g., ABS, traction control, airbag).
• Transmission may be stuck in one gear or shift erratically.
• Gauges on the instrument cluster may behave erratically or not work.
• Scan tool cannot communicate with the ECM/PCM.
• Radio or other interior electronics may act erratically.

Most Likely Causes

1. ECM/PCM Software Glitch 🔴 High Probability Ram released TSB #18-037-16 REV. A specifically to address a no-crank/no-start condition with code U0100 caused by a software issue on models with the 68RFE transmission (DG7 sales code).
   How to confirm: A dealership can check the vehicle's current software calibration number against the one specified in the TSB. If it's an older version, the update is needed.
   Typical fix: The dealership performs a software reflash of the Powertrain Control Module.
   Est. part cost: $0-$200 (Labor for the reflash)
2. Corroded or Damaged ECM/PCM Wiring/Connectors 🟡 Medium Probability The ECM is mounted on the driver's side of the engine block, and its large connectors (a 60-pin C1 and 50-pin C2) are highly susceptible to moisture, oil, and road grime intrusion. This leads to corrosion on the pins and terminals, disrupting communication. Forum users frequently report finding greenish or whitish powder-like corrosion inside these connectors.
   How to confirm: Disconnect the battery, then unplug the main C1 and C2 connectors from the ECM. Visually inspect the pins and sockets on both the harness side and the ECM side for any signs of corrosion, moisture, or bent pins.
   Typical fix: Clean the connector pins and sockets carefully with electrical contact cleaner and a small, soft brush. Apply dielectric grease before reconnecting to prevent future corrosion. In severe cases, the connector pigtail or individual terminals may need to be replaced. A Mopar repair kit for the 60-way C1 connector is available under part number 05135640AA.
   Est. part cost: $10-$150 (For cleaner, grease, or a pigtail kit)
3. Faulty Totally Integrated Power Module (TIPM) ⚪ Low Probability → Shop Fuse Box The TIPM is a known weak point on many Chrysler, Dodge, and Ram vehicles of this era. It acts as the central electrical hub, and internal failures of its relays or circuit board can disrupt power to the ECM or corrupt the CAN bus network, directly triggering U-codes like U0100.
   How to confirm: Diagnosis is complex. It often involves checking for power at specific fuses that feed the ECM and ruling out all other causes. A mechanic may perform a TIPM reset or use a diagnostic tool to check for internal TIPM faults. Symptoms like erratic fuel pump behavior, lights, or wipers often point to the TIPM.
   Typical fix: Replacement of the TIPM with a new or remanufactured unit that is programmed to the vehicle's VIN. A common part number for this application is 68243265AA.
   Est. part cost: $400-$1200
4. Poor Battery Voltage or Bad Grounds ⚪ Low Probability → Shop Vehicle Battery The dual-battery system and complex electronics in the Cummins Ram are sensitive to low voltage. A weak battery or corroded ground straps can cause unpredictable communication errors across the CAN bus. Key ground locations are from the battery to the body, and from the engine block to the chassis frame.
   How to confirm: Test both batteries individually; each should be above 12.4V with the engine off. Load test the batteries to ensure they are healthy. Inspect and clean the main battery terminals and all major ground straps from the engine to the chassis for corrosion and tightness.
   Typical fix: Recharge or replace weak batteries. Disassemble, clean, and tighten all main ground connections.
   Est. part cost: $5-$600 (For cleaning supplies or new batteries)

Rare But Worth Checking

• Failed ECM/PCM: While possible, the Engine Control Module itself is rarely the point of failure. It should only be considered after all wiring, software, and power/ground issues have been thoroughly ruled out. An internal ECM failure can be caused by water intrusion or an internal short.
• Failed ABS Module: → Shop ABS Control Module In some cases, a failing Anti-lock Brake System (ABS) module can broadcast corrupt data onto the CAN bus, causing a network-wide communication failure that logs a U0100 code. A user on RamForum.com reported that replacing a faulty ABS module resolved their U0100 and no-start issue.

Diagnosis Steps

1. Check for Technical Service Bulletins (TSBs). The first step for this specific vehicle is to confirm with a dealer if the software update from TSB #18-037-16 REV. A applies and has been performed.
2. Perform a full vehicle scan to see which other modules are reporting a loss of communication. This helps determine if the issue is isolated to the ECM or is a network-wide problem.
3. Check Battery and Grounds. Test both batteries and their connections. Inspect the main ground straps located on the passenger side body, driver side body, and from the engine block to the frame.
4. Inspect ECM Connectors. Disconnect the battery, then unplug and meticulously inspect the 60-pin C1 and 50-pin C2 connectors at the ECM for any signs of corrosion, moisture, or bent/damaged pins.
5. Check CAN Bus Integrity. With the battery disconnected, use a multimeter to check the resistance between Pin 6 (CAN High) and Pin 14 (CAN Low) at the OBD-II diagnostic port. A healthy network should read approximately 60 ohms. A reading of 120 ohms suggests an open circuit or a missing terminating resistor, while a reading near 0 ohms indicates a short between the CAN lines.
6. Check for Power at the ECM. Using a wiring diagram, verify that the ECM is receiving battery power and ignition-on power at the correct pins in its connectors. A loss of power from the TIPM can cause the U0100 code.
7. If all wiring, grounds, and power sources are good, and the TSB has been performed, further professional diagnosis of the TIPM or other modules (like the ABS module) is required.

Parts You'll Likely Need

• ECM Software Update — This is the official fix from Ram for the common no-crank/no-start issue associated with U0100 on these trucks, as per TSB #18-037-16 REV. A.
  Trusted brands: Mopar (Dealer Service)
  OEM price range: $100-$200
  Aftermarket price range: N/A
• Totally Integrated Power Module (TIPM) (OEM #68243265AA) — The TIPM is a common failure point on these vehicles and can cause a wide range of communication codes, including U0100, by failing to supply power to the ECM or corrupting the network.
  Trusted brands: Mopar, Dorman
  OEM price range: $800-$1200
  Aftermarket price range: $400-$700
• ECM Connector Repair Kit (OEM #05135640AA) — If corrosion is found in the 60-pin C1 connector at the ECM, this Mopar kit may be needed to replace damaged terminals or the connector housing itself.

Related Codes That Often Appear With This One

• U0101 — Lost Communication with TCM. Since the TCM and ECM are on the same CAN bus, a network-wide issue will often cause both codes to appear together.
• U0140 — Lost Communication with Body Control Module (BCM)/TIPM. This often points towards a faulty TIPM or a problem with the main CAN bus wiring that connects the TIPM to other modules.
• C2206 — Vehicle Configuration Mismatch. This code can appear alongside U0100 when a module like the ABS unit is failing and causing network chaos, as seen in some owner reports.

Technical Service Bulletins (TSBs) & Recalls

• 18-037-16 REV. A

Platform-Specific Known Issues

• A software update is required to fix a no-crank/no-start condition with code U0100, as documented in TSB #18-037-16 REV. A.
• Corrosion in the large 60-pin C1 and 50-pin C2 connectors at the ECM is a frequent problem leading to communication faults. These are located on the driver's side of the engine block and are exposed to the elements.
• Failure of the Totally Integrated Power Module (TIPM) is a well-documented issue on this platform and can be the root cause of the U0100 code by cutting power to the ECM.

Mechanic-Grade Diagnostic Values

• CAN Bus Resistance (Battery Disconnected) — expected: ~60 Ohms. Failure: 120 Ohms indicates an open in the bus or a missing terminating resistor. ~0 Ohms indicates a short between CAN High and CAN Low wires.
• CAN Bus Voltage (Key On, Engine Off) — expected: CAN High (Pin 6 to ground): ~2.7V. CAN Low (Pin 14 to ground): ~2.3V.. Failure: Voltages that are stuck high, low, or at 0V indicate a short to power or ground on that line.
• Ground Circuit Resistance — expected: < 0.1 Ohms. Failure: Higher resistance indicates a poor ground connection, which can cause floating voltages and communication errors.

Scan Tool Commands That Help

• wiTECH or AlfaOBD: Proxy Alignment (Proxi) — This procedure is required after replacing a major control module like the TIPM, ABS module, or Instrument Cluster. It synchronizes the vehicle's configuration across all modules. Failure to perform a proxy alignment can result in a flashing odometer and persistent communication codes.
• wiTECH or JScan/AlfaOBD: ABS Bleed — If the ABS module or HCU is suspected or replaced, this function is necessary to cycle the internal valves and solenoids to properly bleed air from the hydraulic unit after repairs.

Wiring & Ground Locations

• ECM C1 & C2 Connectors — Driver's side of the engine block, below the fuel filter housing.. These are the main data and power connectors for the ECM. They are highly prone to corrosion from water, oil, and road salt, which directly interrupts communication and power, causing U0100.
• Battery to Body Ground — A 10-gauge wire from the negative battery terminal to the body, just above the driver's side headlight assembly.. This is a primary ground point for many electronic modules. Corrosion here can cause widespread electrical issues, including communication faults.
• Engine Block to Frame Ground — A large 2/0 gauge cable from the left front of the engine block to the vehicle frame.. This is the main ground path for the engine and its components, including the ECM. A poor connection here can lead to unstable power for the ECM.
• CAN C Bus Wires — Throughout the engine harness. The CAN C (+) is typically a white wire with a light green stripe, and the CAN C (-) is a white wire with a brown stripe.. These two twisted wires are the physical network. Chafing or shorts in the harness where it routes around the engine or through the firewall can bring down the entire network.

Real Owner Repair Stories

• cumminsforum.com user (2014 Ram 3500 6.7L) — No-start, U0100 code, scan tool would not communicate with ECM.
  ❌ Tried (didn't work) Checking all fuses., Inspecting ECM connectors (they were clean)., Checking battery voltage and grounds.
  ✅ What actually fixed it Found a corroded CAN bus wire inside the main wiring harness loom near the driver's side shock tower. The corrosion was not visible externally. The owner cut open the loom, found the compromised white/green wire, spliced in a new section, and the truck started immediately.
• hdrams.com user (2015 Ram 2500 6.7L) — Truck would intermittently not start, throwing U0100. Wiggling the main engine harness could sometimes make it start.
  ❌ Tried (didn't work) Dealer performed the TSB software update., Cleaned ECM connectors., Replaced both batteries.
  ✅ What actually fixed it The problem was traced to a pin inside the C222 connector, a large, gray, 22-pin inline connector located on the driver's side frame rail. The pin had poor tension, causing an intermittent open on the CAN bus circuit. Replacing the single terminal within the connector resolved the issue permanently.

OEM Part Supersession History

• 68243265AA (and others) → RL243265AA, 68243265AB, 68243265AC — Standard part revisions and remanufacturing.
  Heads up: When replacing the TIPM, the Body Control Module (BCM) may need to be flashed with the latest software to ensure proper functionality with the new or revised TIPM part. Failure to do so can cause feature malfunctions even if the U0100 code is resolved.