U0100 on 2013-2016 Dodge Dart: Causes and Fixes for Lost Communication with ECM/PCM

What's Unique About the 2013-2016 Dodge Dart

The Dodge Dart from this era is particularly known for electrical issues stemming from poor ground connections. Unlike many vehicles where a U0100 code might point directly to a complex module or wiring failure, on the Dart, the root cause is frequently corrosion at the main engine-to-chassis ground points. Owners on forums like dodge-dart.org repeatedly document a sudden no-crank, no-start situation that can be mistaken for a failed starter or PCM, when simply cleaning these ground terminals resolves the entire issue.

Symptoms You May Notice

• Engine will not crank or start (most common symptom).
• Multiple warning lights illuminate on the dashboard simultaneously (Check Engine, ABS, Airbag, etc.).
• Engine stalls while driving, sometimes with no warning.
• Erratic or delayed starting.
• Error messages on the dash, such as 'Engine temperature too high' even when cold.
• Wipers may activate on their own when the fault occurs.
• Scan tool cannot communicate with the PCM, but may communicate with other modules (BCM, TCM).
• Odometer mileage flashing.
🎬 Watch how to perform a proxy alignment to fix a flashing odometer.

Most Likely Causes

1. Poor Engine/Transmission Ground Connection 🔴 High Probability → Shop Transmission Assembly The design and location of the primary engine ground straps make them susceptible to moisture and corrosion over time. This creates high resistance, preventing sufficient current flow for the starter and causing voltage instability for the PCM, triggering a communication loss.
   How to confirm: Perform a voltage drop test on the ground circuit. A simpler method is to use a jumper cable to connect the negative battery terminal directly to a clean metal point on the engine block or transmission case. If the car cranks or starts with the jumper cable in place, the ground connection is faulty.
   Typical fix: Locate the ground bracket on the driver's side of the engine block. Disconnect the 10mm and 13mm bolts, remove the cable terminals, and thoroughly clean the terminals, the bracket, and the mounting surface on the block with a wire brush until all corrosion is gone and bare metal is visible. Applying dielectric grease can help prevent future corrosion.
   Est. part cost: $0-$20
2. Weak or Faulty Battery 🟡 Medium Probability → Shop Vehicle Battery All modern vehicles with complex computer networks are sensitive to low voltage. A battery that is failing or has corroded terminals can cause modules to drop off the communication network during the high current draw of startup, triggering a U0100 code.
   How to confirm: Test the battery with a multimeter. A healthy, fully charged battery should read at least 12.4-12.6 volts with the engine off. A load test, which can be done for free at most auto parts stores, is the most definitive way to confirm battery health.
   Typical fix: Recharge or replace the battery. Clean the battery terminals and cable ends with a wire brush and terminal cleaner.
   Est. part cost: $150-$250
3. Faulty Transmission Range Sensor (PRNDL Switch) 🟡 Medium Probability → Shop Transmission Assembly This sensor tells the PCM which gear the transmission is in (Park, Reverse, Neutral, Drive, Low). If it fails, it may not send a valid 'Park' or 'Neutral' signal, which is a requirement for the PCM to allow the starter to engage. This can cause an intermittent no-crank condition that may be accompanied by U0100 if the network is disrupted by the fault.
   How to confirm: With a capable scan tool, monitor the transmission range sensor data while shifting through the gears. If the data is erratic, shows an invalid position, or reads 'No Selection Active' when in Park, the sensor is likely faulty. This issue often stores specific codes like P0705 or P1C86, which are strong indicators.
   Typical fix: Replace the transmission range sensor. It is located on the outside of the transmission where the shift cable attaches. The replacement involves removing the connector, shift linkage, and two 10mm bolts.
   Est. part cost: $50-$100
4. Corroded or Loose PCM Connectors ⚪ Low Probability The PCM is located on the battery tray under the hood, an area that can be exposed to moisture or battery fumes. Over time, water can get past the connector seals and cause corrosion on the pins, leading to high resistance and communication loss.
   How to confirm: Disconnect the negative battery terminal. Unplug the large electrical connectors from the PCM and carefully inspect the pins and the connector housings for any signs of green or white corrosion, moisture, or bent/damaged pins.
   Typical fix: If corrosion is minor, it can sometimes be cleaned with a specialized electrical contact cleaner and a small brush. If corrosion is severe or pins are damaged, the connector pigtail or the PCM itself may need to be replaced. Applying dielectric grease upon reassembly is recommended.
   Est. part cost: $10-$800
5. Faulty Powertrain Control Module (PCM) ⚪ Low Probability → Shop Engine Control Module (ECM)
   How to confirm: This is a diagnosis of exclusion. If the battery is confirmed good, all power and ground connections to the PCM are verified to be perfect (both voltage supply and voltage drop tests), and the CAN bus wiring is intact, the PCM itself is the likely culprit. This requires advanced diagnostics and should be the last item to consider.
   Typical fix: Replace the PCM. The new module will need to be programmed to the vehicle's VIN and security information by a dealer or a specialized shop with the correct tools.
   Est. part cost: $400-$1000

Rare But Worth Checking

• CAN Bus Wiring Fault:
• Faulty Totally Integrated Power Module (TIPM): → Shop Fuse Box

Diagnosis Steps

1. Check Battery Health: Ensure the battery is fully charged (12.4V+). Have it load tested to confirm it's not failing under load. Clean any corrosion from the terminals and ensure connections are tight.
2. Inspect and Clean Engine Grounds: This is the most critical step for a Dart. Locate the main engine ground straps on the driver's side of the engine block. Disassemble, clean all contact surfaces (terminals, bracket, block) to bare metal with a wire brush, and reassemble securely.
3. Scan for All Codes: Use an advanced scan tool to read codes from ALL modules (BCM, TCM, ABS, etc.), not just the PCM. Look for codes related to the transmission range sensor (P0705) or other communication codes (U0101, U0141).
4. Inspect PCM Connections: Disconnect the battery. Unplug the PCM connectors (located on the battery tray) and inspect for any signs of corrosion, moisture, or damaged pins.
5. Check Fuses: Visually inspect and test all fuses related to the PCM, BCM, and ignition systems in the under-hood fuse box (TIPM). Specifically check fuses F11, F16, F18, and F24 for the PCM.
6. Test CAN Bus Network Integrity: With the battery disconnected, use a multimeter to check for resistance between Pin 6 (CAN-H) and Pin 14 (CAN-L) at the OBD-II port. A healthy network should read approximately 60 ohms. A reading of 120 ohms indicates one of the terminating resistors (usually in the PCM and another module) is offline. An open or shorted reading indicates a wiring problem.
7. Verify PCM Power and Ground: Using a wiring diagram, back-probe the PCM connector to verify that the module is receiving proper battery voltage on its power pins and has a solid ground connection (less than 0.1 volts of drop) on its ground pins.
8. Suspect PCM: If all other steps check out—power is good, grounds are perfect, and the network is intact—the PCM is likely the point of failure. This is a last resort.

Parts You'll Likely Need

• Engine Ground Strap — The original ground connections are prone to corrosion, causing a no-start and U0100 code. Cleaning is often sufficient, but replacing a heavily corroded cable may be necessary.
  Trusted brands: Mopar, Dorman
  OEM price range: $20-$40
  Aftermarket price range: $10-$25
• Transmission Range Sensor (OEM #Mopar 68197124AB) — A common failure point causing intermittent no-crank conditions that can be misdiagnosed as a PCM issue. Often accompanied by code P0705.
  Trusted brands: Mopar, Standard Motor Products
  OEM price range: $70-$90
  Aftermarket price range: $40-$60

Related Codes That Often Appear With This One

• P0705 — Indicates a fault in the Transmission Range Sensor circuit. This sensor's failure can directly cause a no-crank condition, which can be confused with or lead to a U0100 code.
• U0101 — Lost Communication with TCM (Transmission Control Module). Since the TCM and PCM are on the same high-speed CAN-C network and often share power/ground circuits, a fault affecting one can affect the other.
• U0141 — Lost Communication with BCM (Body Control Module). A widespread network failure, often due to a bad ground, power feed, or wiring short, will cause multiple modules to lose communication simultaneously.

Technical Service Bulletins (TSBs) & Recalls

• TSB 18-023-16: Flash: 2.4L Powertrain Diagnostic and System Improvements. Involves reprogramming the PCM, which can address software glitches that may contribute to communication issues.
• TSB 18-020-15 REV. A: Flash: Driveability Enhancements for 1.4L Engine. Addresses symptoms like 'Engine cranks as if it has no compression', which could be related to PCM software logic during a fault.
• Bulletin #08-068-16: This manufacturer update addresses the illumination of U0100-00 (Lost Communication With ECM/PCM) along with U0140-00 and U0101-00 to reduce the potential for misdiagnosis and incorrect module replacement.

Platform-Specific Known Issues

• Owner Experience: The $0 Ground Strap Fix: → Shop Engine Ground Strap Multiple owners on dodge-dart.org report a sudden no-crank/no-start condition. The dashboard lights up, but turning the key does nothing. After towing the car to a shop or home, they discover the issue is heavy corrosion on the engine block ground point. One user describes unbolting the two ground cables from the bracket on the engine, cleaning all contact points with a wire brush until shiny, and reassembling. The car started immediately, solving the U0100 code and saving a costly trip to the dealer.
• Owner Experience: Intermittent No-Crank from Range Sensor: A user on YouTube detailed an intermittent no-crank problem that would happen for weeks at a time. Scanning the vehicle revealed stored history codes P0705 and P1C86 for the transmission range sensor. By monitoring live data, they could see the sensor intermittently failing to report that the car was in 'Park'. Replacing the sensor, a relatively simple job on the outside of the transmission, permanently fixed the starting issue.

Documented NHTSA Reports

• An owner reported in NHTSA ODI #11331197 that every single time the vehicle died while driving or failed to start while parked, they received a U0100 engine code.
• NHTSA ODI #11153349 describes a situation where a vehicle was connected to a scanner and showed errors P2122, U1110, U11BC, U0100, and U0101 in reference to communication with the TCM and PCM.
• In NHTSA ODI #11210296, an owner noted that after driving to a shop, a code reader diagnosed U0100 "Lost Communication with the Engine Control Module."
• NHTSA ODI #11615856 records an instance where an independent mechanic used a scanner and found code U0100 "Lost Communication With ECM/PCM" after a safety concern occurred.

Mechanic-Grade Diagnostic Values

• CAN Bus Resistance (Key Off, Battery Disconnected) — expected: ~60 Ohms. Failure: 120 Ohms indicates a terminating resistor is offline; 0 Ohms indicates a short between CAN-H and CAN-L; Open Loop (OL) indicates a break in the wiring.
• CAN Bus Voltage (Key On) — expected: CAN-H (Pin 6) should average ~2.6-2.7V; CAN-L (Pin 14) should average ~2.3-2.4V.. Failure: Voltages that are stuck high, low, or match each other (e.g., both at 1.8V) indicate a short or module failure.
• PCM Ground Circuit Resistance — expected: < 0.1 Ohms. Failure: Higher resistance indicates a poor ground connection, a primary cause of U0100 on this vehicle.
• PCM Power Supply Voltage (Cranking) — expected: > 10V. Failure: Voltage dropping below 10V during cranking can cause the PCM to drop off the network.

Scan Tool Commands That Help

• AlfaOBD / OBDLink MX+: Proxy Alignment — This function is required after replacing the PCM with a used unit. Failure to perform a proxy alignment will result in a flashing odometer and potentially other stored fault codes due to a VIN mismatch between modules.
• wiTECH (Dealer Tool) or advanced bidirectional scanner: Network Test / View Network Status — This function performs a 'roll call' of all modules on the CAN bus and displays which ones are actively communicating and which are not. This can quickly confirm that the PCM is the module that is offline.

Wiring & Ground Locations

• Main Engine Ground — A bracket on the driver's side of the engine block, with cables connecting to the chassis.. This is the most common failure point. Corrosion here creates high resistance, destabilizing the PCM's power supply and causing it to lose communication, triggering U0100.
• Battery Tray Ground — Under the battery tray in the engine compartment.. This is another primary ground point for engine bay components. It should be inspected and cleaned along with the main engine ground.
• PCM Fuses — In the under-hood fuse box (TIPM). Specifically fuses F11, F16, F18, and F24.. These fuses supply power to the PCM. A blown fuse will cut all power, causing an immediate U0100 and no-start condition.
• PCM Connectors (C1-C4) — Attached to the PCM, which is mounted on the battery tray. On a 2.4L, they are often blue and green.. These are the direct interface to the PCM. Corrosion or damage to the CAN bus pins (CAN-C High/Low) within these connectors will sever communication.

Real Owner Repair Stories

• YouTube user 'South Main Auto LLC' (2014 Dodge Dart, 2.4L) — Crank but no start condition.
  ❌ Tried (didn't work) Checking fuses., Confirming battery and alternator were good., Checking the main ground wire.
  ✅ What actually fixed it The fuel pump relay in the under-hood fuse box was faulty. The owner swapped it with a similar relay from a non-essential accessory to test, and the car started immediately. A new relay permanently fixed the problem.
• YouTube user 'FDT Motors' (2013-2016 Dodge Dart 2.4L) — Flashing odometer and check engine light after installing a used PCM.
  ❌ Tried (didn't work) Using a standard Autel scan tool which could not perform the required function., Going to the dealer, who refused to program a used computer and quoted over $1250 for a new one plus programming.
  ✅ What actually fixed it The owner purchased an OBDLink MX+ bluetooth adapter and the AlfaOBD software for his laptop. Using this combination, he was able to successfully run the 'Proxy Alignment' procedure, which synchronizes the VIN across all modules and stopped the odometer from flashing.

OEM Part Supersession History

• 5150909AB → 5150909AC — Revision or update to the component.
• RL150663AD → 5150955AC — RL prefix often indicates a remanufactured part being replaced by a new part number.
• 68258528AA → 68258528AB — Minor revision.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Excessive Oil Consumption (2.4L Tigershark Engine) 🔴 High — Very common. Subject of class-action lawsuits and TSB 09-003-23. Owners may need to add oil between changes. (Ref: TSB 09-003-23 / XB1 Warranty Extension)
• Shifter Cable Bushing Failure (Automatic Transmission) 🔴 High — Extremely common, affecting nearly 300,000 vehicles. The bushing degrades, causing the shifter cable to detach from the transmission, potentially leading to a rollaway risk. (Ref: NHTSA Recall 19V-293 (Chrysler V34))
• Clutch Master Cylinder Failure (Manual Transmission) 🟠 Medium — Common issue on manual transmission models where the clutch pedal sticks to the floor or loses pressure, preventing shifting. (Ref: Subject of a class-action lawsuit and extended warranty program by FCA.)
• Transmission Control Module (TCM) Failure 🟠 Medium → Shop Transmission Assembly — A recall was issued for the TCM, which could fail and cause the transmission to unexpectedly shift into neutral while driving. (Ref: NHTSA Recall 15V-470)
• Thermostat Failure 🟡 Low — A common cause for the check engine light with code P0128, especially in colder weather.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used PCM from a junkyard can be a cost-effective option, but ONLY if you are prepared to perform a 'Proxy Alignment' procedure yourself. This requires specific software (like AlfaOBD) and a compatible OBD-II adapter (like OBDLink MX+), as most standard shops and all dealers will refuse to program a used module. Used wiring harnesses or connectors are also viable if the original is physically damaged.

Donor-vehicle mileage cap: roughly under 120000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For a PCM, ensure the donor vehicle had the exact same engine, transmission, and model year.
• Check the part number on the PCM sticker to match it as closely as possible.
• Inspect connector pins on the used module for any corrosion or physical damage before purchase.
• For a wiring harness, inspect thoroughly for any cuts, abrasions, rodent damage, or brittle insulation.

OEM-only on this vehicle (don't cheap out):

• Powertrain Control Module (PCM). While used OEM is an option with caveats, avoid aftermarket 'rebuilt' PCMs from unknown brands, as their quality and programming can be unreliable.

Aftermarket brands forum-validated for this vehicle:

• For diagnostic tools, AlfaOBD software paired with an OBDLink MX+ adapter is a community-validated solution for performing dealer-level functions like Proxy Alignment on Dodge/Chrysler vehicles.

Brands owners have reported issues with on this vehicle:

• Generic, no-name 'plug and play' tuners or software systems have been reported to damage ECUs on Chrysler vehicles.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0705 — Transmission Range Sensor Circuit Malfunction; often stored alongside U0100 when the PRNDL switch fails to signal Park/Neutral.
• P1C86 — A transmission-specific code that indicates a fault with the range sensor, frequently appearing with U0100 during no-start events.
• U0101 — Lost Communication with TCM; a companion communication code that may trigger if the network instability affects the transmission module as well as the PCM.
• U0141 — Lost Communication with Body Control Module (BCM); often seen when low voltage or ground issues cause multiple modules to drop off the CAN bus.

Frequently Asked Questions