C1406 on 2023 Ram 1500: Transfer Case Brake Control Circuit Open Causes and Fixes

What's Unique About the 2023-2023 Ram 1500

For the 5th generation Ram 1500 (DT), electrical issues, particularly related to module communication and connector integrity, are a recurring theme in technical service bulletins. Ram has issued TSBs for this generation that address a wide array of DTCs, including C1406, stemming from issues as simple as improperly seated connectors on the Drivetrain Control Module (DTCM) or the transfer case itself. This suggests that before suspecting major component failure, a thorough check of the wiring and connectors is more critical on these trucks than on some other vehicles. The CAN bus communication network on these modern trucks means that one loose connector or damaged wire can cause widespread, confusing electronic issues.

Diagnostic Flowchart

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

Symptoms You May Notice

• Malfunction Indicator Lamp (MIL) or check engine light is on
• "Service 4WD" message displayed in the instrument cluster
• Inability to shift into or out of 4WD modes (4HI, 4LO)
• Four-wheel drive system is disabled
• Traction control light may be illuminated and system disabled.

Most Likely Causes

1. Loose or Damaged Wiring Connector 🔴 High Probability Ram has issued multiple TSBs (like #0823723 and RSU 22-226) specifically for loose or improperly seated connectors on the transfer case shift motor and the Drivetrain Control Module (DTCM) causing this and other codes. This is the most widely reported cause by both technicians and owners.
   How to confirm: Visually inspect the wiring harness and connectors at the transfer case motor and the DTCM. The DTCM is located under the driver's side dash, near the top of the floorboard. Perform a 'push-pull-push' test on the connectors to ensure they are fully seated.
   Typical fix: Securely reconnect the loose connector. If the connector or wiring is damaged, it will need to be repaired or replaced.
   Est. part cost: $0 - $50
2. Failed Drivetrain Control Module (DTCM) 🟡 Medium Probability The DTCM is the central computer for the 4WD system. Like any electronic module, it can fail internally. Some service procedures point to replacing the DTCM if all wiring and the transfer case motor check out.
   How to confirm: After confirming the wiring and transfer case motor are good, a technician with a compatible scan tool (wiTECH) can perform advanced diagnostics. If the module fails to communicate or actuate the motor correctly despite good inputs and outputs, it is likely faulty.
   Typical fix: Replace the Drivetrain Control Module. This may require programming by a dealership or a qualified shop.
   Est. part cost: $150 - $250
3. Failed Transfer Case Motor/Actuator ⚪ Low Probability → Shop Transfer Case Motor The 'brake control' circuit is internal to the transfer case motor assembly. An internal failure in this assembly can cause an open circuit, though it is less common than wiring issues for this specific code.
   How to confirm: A technician can test the motor's internal circuits for resistance and continuity using a multimeter. A scan tool can also be used to command the motor to actuate while monitoring its feedback.
   Typical fix: Replace the transfer case motor/actuator assembly.
   Est. part cost: $70 - $200

Diagnosis Steps

1. Check for any Technical Service Bulletins (TSBs) related to your vehicle's VIN. TSBs #0823723 and RSU 22-226 (also released as TSB 08-094-22) are highly relevant.
2. Read all DTCs from all modules to see if other related codes are present, especially communication codes like U0102-00.
3. Locate the Drivetrain Control Module (DTCM). On 2018+ Ram 1500s, it is located under the driver's side dash, above the pedals, often behind a small plastic cover. It has one blue and one white connector.
4. Inspect the DTCM connectors. Disconnect, check for damage or corrosion on the pins, and firmly reconnect them, ensuring they are fully seated. The white connector has a red safety tab that must be pulled out slightly before removal. Perform a 'push-pull-push' test as recommended by the TSB.
5. Locate and inspect the wiring harness connector at the transfer case motor. Check for damage, corrosion, or loose wires. Perform a 'push-pull-push' test to ensure it is secure.
6. If the connectors and wiring appear intact, use a multimeter to test the 'Transfer Case Brake Control' circuit for continuity between the DTCM and the transfer case motor connector, following the vehicle's specific wiring diagram.
7. If wiring is confirmed to be good, the fault is likely with either the transfer case motor assembly or the DTCM itself. Advanced diagnostics with a scan tool are required to test these components individually.

Parts You'll Likely Need

• Drivetrain Control Module (DTCM) (OEM #68483995AD) — If wiring and the transfer case motor are confirmed to be good, a faulty DTCM is a likely cause. Connector issues are common, but internal module failure can also occur.
  Trusted brands: Mopar
  OEM price range: $150-$220
  Aftermarket price range: N/A
• Transfer Case Gear Motor (OEM #68402358AA) — The brake control circuit is part of the transfer case motor. An internal failure can cause this code, though it's less common than wiring issues for this specific vehicle.
  Trusted brands: Mopar
  OEM price range: $70-$110
  Aftermarket price range: $50-$90

Related Codes That Often Appear With This One

• C140A-13 — This code for 'Transfer Case Motor Control-Circuit Open' is often listed in the same TSBs as C1406, indicating they share a common cause, likely a wiring connector issue.
• U0102-00 — This code for 'Lost Communication With Transfer Case Control Module' can appear if the DTCM connector is loose, which also causes the C1406 code.
• C1406-11 — This variant indicates a 'Circuit Short to Ground' and can be caused by the same faulty connectors or wiring harness as the 'Circuit Open' variant.
• C1406-15 — This variant indicates a 'Circuit Short to Battery or Open' and is also listed in TSBs related to DTCM connector issues.
• C1406-92 — This variant means 'Performance Or Incorrect Operation' and is also linked to the DTCM connector TSB.

Technical Service Bulletins (TSBs) & Recalls

• 0823723: Transfer Case Shift Motor Wire Harness Connector Not Secured, causing C1406-13 and other codes.
• RSU 22-226 / TSB 08-094-22: Drivetrain Control Module (DTCM) Connector Issue, causing C1406-15, C1406-92, C1406-11, and other codes due to improperly seated connectors.

Platform-Specific Known Issues

• TSB #0823723 and RSU #22-226 specifically call out improperly seated electrical connectors on both the transfer case motor and the Drivetrain Control Module (DTCM) as a cause for a group of transfer case-related DTCs, including C1406. The recommended fix is to perform a 'push-pull-push' test on the connectors to ensure they are secure.
• TSB 08-094-22 (RSU 22-226) applies to vehicles built on or after August 17, 2022, and on or before August 18, 2022, highlighting a very specific manufacturing window where this DTCM connector issue was prevalent.

Mechanic-Grade Diagnostic Values

• Resistance of Transfer Case Brake Control Circuit (e.g., T301 Switched Battery Solenoid Supply) — expected: Above 5.0 Ohms between the circuit and ground.. Failure: A resistance below 5.0 Ohms indicates a short to ground.
• Continuity of Transfer Case Brake Control Circuit (e.g., T301 or T317) — expected: Below 5.0 Ohms between the DTCM connector and the transfer case motor connector.. Failure: Resistance above 5.0 Ohms indicates an open circuit.
• Resistance of Transfer Case Brake Solenoid — expected: Approximately 21 Ohms between pin 6 (A940 Fused B+) and pin 3 (T300 Brake Signal) at the shift motor assembly connector.. Failure: A reading significantly different from 21 Ohms may indicate a faulty solenoid within the motor assembly.

Hidden / Shadow Codes Worth Checking

• C1406-11: Transfer Case Brake Control - Circuit Short To Ground. (see via Standard professional scan tool, like wiTECH. This is technically a 'symptom byte' which provides specific fault details.)
• C1406-12: Transfer Case Brake Control - Circuit Short To Battery. (see via Standard professional scan tool. This 'symptom byte' indicates the circuit is shorted to a power source.)
• C1406-15: Transfer Case Brake Control - Circuit Short To Battery Or Open. (see via Standard professional scan tool, like wiTECH. This symptom byte is explicitly mentioned in TSB 08-212-22 for the DTCM connector issue.)
• C1406-92: Transfer Case Brake Control - Performance Or Incorrect Operation. (see via Standard professional scan tool, like wiTECH. This symptom byte is also listed in TSB 08-212-22 related to the DTCM connector.)

Scan Tool Commands That Help

• wiTECH: Actuate T-Case Motor Solenoid Lock — This bidirectional command is used to test the transfer case brake control circuit. After clearing DTCs, a technician can command the solenoid on and use a test light to verify if voltage is correctly being sent from the DTCM to the transfer case motor connector.
• wiTECH: Clear All DTCs — This is a critical step when diagnosing. If the transfer case motor or DTCM connectors are disconnected, DTCs will be set. These must be cleared before attempting to actuate components, as the DTCM may disable the output circuit as a failsafe.
• wiTECH: Restore Configuration and Align Proxi — This procedure may be required after replacing and reprogramming certain modules to ensure all vehicle systems recognize the new component and its configuration.

Wiring & Ground Locations

• DTCM (Drivetrain Control Module) — Located under the driver's side dash, above the pedals. It has one blue and one white connector. On some HD trucks, it is in the passenger footwell area.. This is the control module for the 4WD system. Loose connectors at this module are the number one cause of C1406 and related codes, per multiple TSBs.
• Transfer Case Motor Connector (C1) — The electrical connector on the transfer case shift motor, located on the transfer case itself.. This is the other end of the circuit from the DTCM. A loose or corroded connector here will cause an open or short, triggering the code. The diagnostic procedure involves testing for voltage and resistance at this connector.
• T301 / T300 Circuit — This is the circuit wire for the 'Switched Battery Solenoid Supply' or 'Brake Signal' running between the DTCM and the transfer case motor connector.. This specific wire is what must be tested for opens, shorts to ground, or shorts to voltage when diagnosing C1406 variants.
• T317 Circuit — This is the circuit wire for the 'Transfer Case Motor Lock Signal' running between the DTCM and the transfer case motor connector.. This is the diagnostic input/feedback circuit. The DTCM monitors this circuit to confirm the brake's status. A fault on this wire can also cause C1406.

Real Owner Repair Stories

• Reddit user on r/GrandCherokee (Jeep Grand Cherokee (year not specified, but similar platform)) — Intermittent 'Service 4WD' light and traction control light.
  ❌ Tried (didn't work) Replacing the main battery did not fix the issue, as electrical codes returned.
  ✅ What actually fixed it The dealership diagnosed a C1406-11 (Circuit Short to Ground) and replaced the transfer case actuator/motor, which resolved all symptoms.
• YouTube video by MT406 Mechanics (2012 Jeep Grand Cherokee) — 'Service 4WD' light illuminated, code C1406-11 stored.
  ❌ Tried (didn't work) The diagnostic process involved testing the module's output directly.
  ✅ What actually fixed it Using a scan tool to actuate the motor showed no change in output voltage at the module's connector pins, indicating a failed Final Drive Control Module (DTCM). Replacing the module fixed the issue.

OEM Part Supersession History

• 68277415AC, 68277415AD, 68277415AG, 68277415AH, 68277415AI, 68277415AJ, 68277415AK, 68277415AL, 68277415AM, 68277415AN, 68277415AO, 68277415AP, 68483995AC → 68483995AD — These part numbers represent a long series of revisions to the Drivetrain Control Module (DTCM) for 2019-2024 Ram 1500s. Supersessions typically involve hardware updates or software compatibility improvements to address field issues.
  Heads up: While all parts in this list are superseded by the latest version, using an older, un-updated module from a salvage yard could re-introduce known issues. It is always recommended to use the latest part number (68483995AD) for replacement.

Model Year Variations Within This Range

• 2022 (for 2023 Model Year): Per TSB 08-094-22 (also RSU 22-226), Ram 1500s built on or after August 17, 2022, and on or before August 18, 2022, have a known manufacturing issue where the DTCM connectors may not be fully seated, causing C1406 and a host of other communication and circuit codes.