U0402 on 2013-2015 Dodge DART: Implausible TCM Data Causes and Fixes

What's Unique About the 2013-2015 Dodge DART

The Dodge Dart from this era, built on the FCA CUSW platform, is known for specific communication issues, particularly in models with the 2.4L engine. FCA (the parent company of Dodge) released several Technical Service Bulletins (TSBs) indicating that a PCM software update is often required to correct the logic that interprets data from the TCM. 🎬 See how to diagnose and fix the U0402 invalid data code. This strongly suggests the problem is frequently not a hardware failure but a correctable software flaw that FCA has actively addressed. The TSBs note that after the PCM flash, the TCM software must also be verified and updated if necessary. A key difference is the transmission type: 2.0L/2.4L models use a conventional automatic with an integrated TCM, while the 1.4L Turbo uses a Dual Dry-Clutch Transmission (DDCT) with a separate hydraulic controller (Smart Drive Unit) that can fail and mimic TCM issues.

Diagnostic Flowchart

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

Symptoms You May Notice

• Check Engine Light is on
• Transmission warning light is illuminated
• Erratic or harsh shifting
• Vehicle enters 'limp mode' (stuck in one gear)
• Delay or failure to engage a gear when shifting from Park.
• Flashing gear indicator on the dashboard
• Car unexpectedly shifts into Neutral while driving
• Traction control or other warning lights may also illuminate.

Most Likely Causes

1. Outdated Powertrain Control Module (PCM) Software 🔴 High Probability Manufacturer TSBs #18-022-17 REV. A and #18-023-16 directly list U0402 as a code that can be resolved with a PCM software update for the 2.4L engine. This is the most documented and common fix.
   How to confirm: A Dodge dealership or a properly equipped independent shop can check the current software calibration ID of the PCM and compare it against the latest version available from FCA using a tool like wiTECH.
   Typical fix: Flashing the PCM with the updated software calibration. The TSBs note that the TCM software level should also be checked and updated as needed after the PCM flash. The flash process takes approximately 5-6 minutes once connected.
   Est. part cost: $0
2. Failing Transmission Control Module (TCM) 🟡 Medium Probability The TCM itself can fail due to internal hardware issues like cracked solder joints or moisture ingress, causing it to send corrupted data packets onto the vehicle's communication network. There was also a recall for some Dart models due to a faulty TCM mounting bracket that could lead to issues. This applies primarily to the 2.0L and 2.4L engine models.
   How to confirm: After ruling out software and wiring, a technician may use a high-level scan tool to monitor data from the TCM. If the data is clearly erratic, the module is unresponsive, or it fails a bidirectional test, it is likely faulty.
   Typical fix: Replacement of the TCM. The new module must be programmed to the vehicle's VIN and undergo a 'quick learn' procedure.
   Est. part cost: $300-$700
3. Wiring or Connector Issues ⚪ Low Probability Harnesses can be subject to chafing, and connectors can suffer from corrosion or water intrusion. Owners on forums specifically mention checking the main TCM connector for loose pins and the harness routing near the transmission for any signs of rubbing or damage. The STAR connector, a central CAN bus junction point, is another potential failure point.
   How to confirm: Visually inspect the wiring harness and connectors between the PCM and TCM for any signs of damage, corrosion, or loose pins. Pay close attention to the large connector at the TCM itself. A multimeter can be used to check for continuity and proper voltage/ground at the TCM connector pins.
   Typical fix: Repairing the damaged section of the harness or cleaning/replacing the affected connector.
   Est. part cost: $10-$100
4. Low Battery Voltage or Poor Grounds ⚪ Low Probability All modern electronic modules are sensitive to voltage. A weak battery, failing alternator, or corroded ground connection can cause modules to behave erratically and send invalid data. This is a common cause for a variety of network codes on many modern cars, not just the Dart.
   How to confirm: Test the battery and charging system. Ensure battery voltage is above 12.4V with the engine off and between 13.5V-14.5V with the engine running. Check the main battery terminals, chassis ground (e.g., G100, G102), and the ground strap to the transmission for tightness and corrosion.
   Typical fix: Replacing a weak battery, repairing the charging system, or cleaning/tightening ground connections.
   Est. part cost: $5-$250

Rare But Worth Checking

• Failed Powertrain Control Module (PCM): While the PCM is the module *receiving* the bad data, it can fail internally in rare cases, causing it to misinterpret otherwise good data. This is uncommon and should only be considered after all other possibilities are exhausted.
• Failed Smart Drive Unit (SDU) (1.4L Turbo DDCT Only): On models with the 1.4L Turbo engine and Dual Dry-Clutch Transmission (DDCT), the hydraulic control unit, called the Smart Drive Unit (SDU), can fail. Symptoms are nearly identical to a TCM failure (limp mode, no gear engagement) and can be misdiagnosed as a bad TCM or transmission.

Diagnosis Steps

1. Scan for all stored trouble codes in all modules to see if other communication codes are present.
2. Check for applicable Technical Service Bulletins (TSBs) for your vehicle's VIN. Specifically, inquire about TSBs #18-022-17 REV. A and #18-023-16.
3. If a relevant TSB exists for a software update, have a dealership perform the PCM reflash. This is the most likely solution and should be the first step. Ensure they also check for any required TCM software updates.
4. If no TSB applies or the update doesn't fix the issue, test the battery and charging system to ensure stable voltage (13.5V-14.5V when running).
5. Inspect the main engine and transmission ground straps for corrosion and tightness. Key grounds are G100 and G102 at the front of the engine compartment.
6. Visually inspect the wiring harness and connectors between the TCM and PCM. Pay special attention to the main connector on the TCM for any damage, moisture, or corrosion.
7. Test the CAN bus network. With the battery disconnected, measure resistance between CAN-H and CAN-L pins at the OBD-II port; it should be approximately 60 Ohms. With the ignition on, CAN-H and CAN-L should both read approximately 2.5V.
8. If all wiring and power sources are good, the fault likely lies with the Transmission Control Module (TCM) itself (on 2.0L/2.4L models) or the Smart Drive Unit (SDU) (on 1.4L models).
9. As a final step, consider a faulty PCM, though this is rare.

Parts You'll Likely Need

• Transmission Control Module (TCM) (OEM #68258732AC (supersedes 68258732AB, 05150807AI and others)) — If a software update doesn't resolve the code, the TCM is the next most likely component to have failed, causing it to send invalid data. This part is specific to the 2.4L engine with the 6-speed automatic transmission.
  Trusted brands: Mopar
  OEM price range: $450-$800
  Aftermarket price range: $300-$500

Related Codes That Often Appear With This One

• U0140 — This code for 'Lost Communication With Body Control Module' is listed in the exact same TSBs (#18-022-17 REV. A and #18-023-16) as U0402, suggesting a common root cause in the PCM software that affects communication with multiple modules.
• P0133 — O2 Sensor Slow Response. Also listed in TSBs #18-022-17 REV. A and #18-023-16, indicating the PCM software update addresses multiple potential faults simultaneously.
• P0456 — EVAP System Small Leak. Also listed in TSBs #18-022-17 REV. A and #18-023-16, indicating the PCM software update addresses multiple potential faults.
• P2172 — High Airflow/Vacuum Leak Detected. Also listed in TSBs #18-022-17 REV. A and #18-023-16, indicating the PCM software update addresses multiple potential faults.

Technical Service Bulletins (TSBs) & Recalls

• 18-022-17 REV. A: Addresses a group of diagnostic trouble codes, including U0402, that can be corrected by a PCM software update on 2014-2015 models with the 2.4L engine. Also applies to the 2015 Chrysler 200.
• 18-023-16: Addresses a group of diagnostic trouble codes, including U0402, that can be corrected by a PCM software update on 2013-2015 models with the 2.4L engine.

Platform-Specific Known Issues

• Dodge issued TSB #18-022-17 REV. A for 2014-2015 models and #18-023-16 for 2013 models, which addresses code U0402 (among others) with a PCM software update. This should be the first diagnostic check.
• These TSBs apply specifically to vehicles with the 2.4L engine (Sales Codes ED6 or ED8).
• The TSB procedure explicitly notes that after reprogramming the PCM, the technician must also verify the TCM is programmed with the latest available software.

Mechanic-Grade Diagnostic Values

• CAN Bus Network Resistance — expected: ~60 Ohms. Failure: A reading of ~120 Ohms indicates one of the two terminating resistors is offline. A reading significantly different from 60 Ohms suggests a wiring issue.
• TCM Power Supply Voltage (Ignition On) — expected: Greater than 10V, typically 11.5V - 13.5V. Failure: Voltage below 10V indicates a problem with the power supply circuit, fuse, or ground.
• CAN Bus Voltage (Ignition On) — expected: CAN-H and CAN-L should both be approximately 2.5V. Failure: Voltages that are stuck high, low, or at battery/ground potential indicate a short in the CAN wiring.
• TCM Sensor Ground Circuit Resistance — expected: Below 5.0 Ohms. Failure: Resistance above 5.0 Ohms indicates an open or high resistance in the ground circuit for a sensor, which can cause bad data.

Scan Tool Commands That Help

• wiTECH or equivalent (Autel, Snap-On): TCM Bidirectional Test — Early in diagnosis to confirm if the TCM can receive commands to shift gears while stationary. If it fails to respond, it points towards a communication or internal TCM fault.
• wiTECH or equivalent: Reset Data Group / Quick Learn — This is a mandatory procedure after replacing the TCM on a Dodge Dart. It resets adaptations and forces the module to relearn shift points and clutch engagement.
• wiTECH or equivalent: Clutch Learn Procedure — Specifically for the Dual Dry-Clutch Transmission (DDCT) in 1.4L Turbo models, this must be performed after replacing the TCM or SDU to learn the clutch contact points.
• wiTECH or equivalent (Autel): Hydraulic Circuit Bleed — On 1.4L DDCT models, this function must be run before disconnecting the Smart Drive Unit (SDU) to depressurize the system and pump fluid back to the reservoir.

Wiring & Ground Locations

• TCM (Transmission Control Module) — Inside the cabin, on the passenger side, behind the carpet near the front footwell area.. This is the module sending the implausible data. Its location inside the cabin makes it less prone to engine bay heat/vibration but still susceptible to water intrusion from a leaking heater core or windshield.
• G100 / G102 — Located on the left front of the engine compartment.. These are primary chassis ground points. A corroded or loose connection here can cause fluctuating voltage to multiple modules, including the PCM and TCM, leading to communication errors.
• TCM Fuses — Underhood Power Distribution Center (fuses f05, F15) and the interior fuse box under the steering wheel (fuse #25).. A blown or loose fuse will cut power to the TCM, causing it to stop communicating entirely or send corrupt data as power fluctuates.
• STAR Connector — Under the left side of the dash, near the steering column.. This is a central junction point where multiple CAN bus lines meet. A loose connection or corrosion within this connector can disrupt communication between many modules, including the PCM and TCM.

Real Owner Repair Stories

• Reddit user post on r/dodgedart (2013 Dodge Dart Limited 1.4L Turbo with DDCT, 138k miles) — Car wouldn't hold a gear, gear indicator blinking, 'Service Trans' message on dash, would shift to neutral.
  ❌ Tried (didn't work) Dealer diagnosed a bad hydraulic pump., A second shop diagnosed a complete transmission failure.
  ✅ What actually fixed it The owner replaced the 'Smart Drive Unit' (SDU), which is the hydraulic control unit for the DDCT. This was a plug-and-play part that resolved all symptoms.

When the Usual Fixes Don't Work

• While the TSBs and common knowledge point heavily towards PCM software updates or TCM failure for the U0402 code, real-world owner experiences provide a critical counterpoint for the 1.4L Turbo models. In at least one documented case, two different repair shops, including a dealership, incorrectly diagnosed the issue as a hydraulic pump and then a full transmission replacement. The actual fix was replacing the Smart Drive Unit (SDU), a separate hydraulic controller specific to the dual-clutch transmission. This demonstrates that for the 1.4T engine, the diagnostic path must include the SDU as a likely culprit for U0402 symptoms, even if the code points to data from the 'TCM'.

OEM Part Supersession History

• Multiple (e.g., 05150807AD, 68258732AA) → 68258732AC — Revisions to improve reliability and address communication faults.
  Heads up: This part number series is for the 6-speed automatic transmission paired with the 2.0L and 2.4L engines. It is NOT compatible with the 1.4L Turbo engine's Dual Dry-Clutch Transmission (DDCT).

Model Year Variations Within This Range

• 2013-2016: The engine choice dictates the transmission and control system architecture. The 2.0L and 2.4L engines use a Powertech 6F24 6-speed automatic with a traditional TCM. The 1.4L Turbo engine uses a C635 Dual Dry-Clutch Transmission (DDCT) which has a separate hydraulic controller called the Smart Drive Unit (SDU) in addition to the TCM. Diagnostic paths for U0402 are significantly different between these powertrains.