2021 Jeep Wrangler DTCM Update for 4WD System Issues

Owners of the 2021 Jeep Wrangler may experience a Malfunction Indicator Lamp (MIL) illumination accompanied by specific 4WD system malfunctions. This issue is detailed in Technical Service Bulletin (TSB) 08-366-26, which provides a software update for the Drivetrain Control Module (DTCM) to resolve these concerns. The TSB applies to vehicles equipped with Command-Trac Part Time 4WD (Sales Code DHN), 2.72:1 Select-Trac Full Time 4WD (Sales Code DHP), 4:1 Rock-Trac HD Part Time 4WD (Sales Code DHW), or 4:1 Rock-Trac HD Full Time 4WD (Sales Code DHF) systems.

Symptoms

Customers may observe a "Malfunction Indicator Lamp (MIL) illumination" on their dashboard. This is often accompanied by the Diagnostic Trouble Code (DTC) C147B-92. Beyond the MIL, owners might notice several other symptoms related to the 4WD system, indicating a need for the Jeep Wrangler DTCM update.

These symptoms include:

• "4WD system warning lights", "service messages", or "flashing indicators" displayed in the Instrument Panel Cluster (IPC).
• The "vehicle does not engage 4WD properly", which can impact off-road capability and vehicle performance.

Fault Codes / DTCs

The primary diagnostic trouble code associated with this issue is:

Code	Description	Module
C147B-92	Front Axle Disconnect Sensor Performance or Incorrect Operation	DTCM

This DTC indicates a problem with the front axle disconnect sensor, which is managed by the Drivetrain Control Module (DTCM).

Diagnosis / Trigger Conditions

To properly diagnose the issue, technicians will use a wiTECH scan tool along with the diagnostic procedures available in DealerCONNECT/Service Library. The initial step involves verifying that all related systems are functioning as designed. If any DTCs or symptom conditions other than those listed in TSB 08-366-26 are present, they must be recorded and addressed before proceeding with the DTCM software update.

If the customer's reported symptoms match those described in the bulletin, the repair procedure for the Jeep Wrangler DTCM update can be initiated.

Repair Procedure Summary

The resolution for the "Jeep Wrangler DTCM update" involves reprogramming the Drivetrain Control Module with the latest available software. This process requires specific attention to battery voltage to ensure a successful update.

Before starting the reprogramming, a battery charger must be installed to maintain the battery voltage above 13.2 volts. It is crucial not to allow the charging voltage to exceed 13.5 volts during the flash process, as this could cause issues. If the flash process is interrupted or aborted for any reason, it must be restarted from the beginning.

The steps for the repair are:

1. Reprogram the DTCM using the wiTECH Diagnostic Application with the most current software. If any issues arise during the module flashing, a ticket should be submitted to the Helpdesk, accessible through the Help menu.
2. After the reprogramming is complete, all Diagnostic Trouble Codes (DTCs) that may have been set in any module due to the reprogramming process must be cleared. The wiTECH application is designed to automatically present all DTCs after the flash, allowing for easy clearing.

For vehicles in the South America (SA) market, it is important to note that after applying this TSB, there is no requirement to send DID-I or DID-A information.

Required Tools or Parts

The primary tool required for this service is:

• wiTECH or Equivalent: A diagnostic scan tool necessary for communicating with the vehicle's modules and performing the software reprogramming.

What Owners Should Know

This technical service bulletin addresses a specific software-related issue with the Drivetrain Control Module. The repair, which involves a software update, is typically reimbursable within the provisions of the vehicle's warranty. Dealers are instructed to use failure code CC (Customer Concern) when processing claims for this TSB, provided the customer's concern matches the symptoms outlined in the bulletin.

Owners experiencing a Malfunction Indicator Lamp, DTC C147B-92, or 4WD system malfunctions should contact their authorized Jeep dealer to schedule an appointment. The labor time for this specific operation, Module, Drivetrain Control (DTCM) - Reprogram, is estimated at 0.3 hours.

---

Source: NHTSA ID 11038489