2021 Jeep Wrangler PCM Update TSB 18-005-26

Jeep has issued Technical Service Bulletin (TSB) 18-005-26 REV. A to address various performance concerns and diagnostic trouble codes affecting the 2021 Jeep Wrangler. This bulletin, dated February 17, 2026, supersedes the previous TSB 18-005-26 issued on January 29, 2026, and focuses on a critical 2021 Jeep Wrangler PCM update.

The TSB applies to 2021 Jeep Wrangler vehicles equipped with the 3.6L V6 24V VVT Engine UPG I W/ESS (Sales Code ERC). It is applicable to vehicles in North and South America, Enlarged Europe, Middle East & Africa, India & Asia Pacific, and China markets.

Symptoms

Owners of affected 2021 Jeep Wrangler vehicles may experience a Malfunction Indicator Lamp (MIL) illumination on the dashboard. This is often accompanied by specific Diagnostic Trouble Codes (DTCs) being set. Additionally, customers might observe other issues related to the vehicle's performance.

Commonly reported symptoms include:

• A "Service Transmission" message appearing in the Instrument Panel Cluster (IPC) due to clutch slip detection, primarily in manual transmission models.
• The vehicle entering "limp home mode."
• A "spark knock/detonation sound from the engine at idle."
• Customers might experience wheel spin or slippage, which the PCM could misinterpret as excessive clutch slippage, leading to the IPC message to prevent clutch damage.

Fault Codes / DTCs

This 2021 Jeep Wrangler PCM update specifically addresses vehicles that have set one or more of the following Diagnostic Trouble Codes:

Code	Description	Conditions
P08A6	Gear Lever Position Sensor System – Multiple Sensor Correlation	Manual Transmission and North America Only
P152F	Engine Hood Switch 2 / Engine Hood Switch 1 Correlation	North America Only
P0300	Multiple Cylinder Misfire	All markets

Diagnosis

When diagnosing these symptoms, technicians are instructed to use a wiTECH Scan Tool. This tool, along with appropriate Diagnostic Procedures available in DealerCONNECT/Service Library, helps verify that all related systems are functioning as designed. If other DTCs or symptom conditions are present, they should be recorded and addressed before proceeding with the TSB's repair.

Repair Procedure Summary

The core of the repair involves reprogramming the Powertrain Control Module (PCM) with the latest available software. This 2021 Jeep Wrangler PCM update is designed to resolve the underlying software issues causing the reported symptoms and DTCs.

Key steps for the repair include:

1. Battery Preparation: Install a battery charger to ensure the battery voltage remains between 13.2 volts and 13.5 volts throughout the flash process. Maintaining stable voltage is crucial for a successful update.
2. PCM Reprogramming: Reprogram the PCM using the latest software available via the wiTECH Diagnostic Application. If any issues arise during the flashing process, technicians are advised to submit a ticket to the Helpdesk.
3. DTC Clearance: After the PCM update, all Diagnostic Trouble Codes that may have been set in any module due to the reprogramming must be cleared using the wiTECH application.

This TSB also includes other software enhancements, such as an engine oil pump operating in high-pressure mode with cold engine oil. This aims to improve valvetrain component reliability.

Important Warnings

• Battery Voltage: It is critical to install a battery charger and ensure the battery voltage does not drop below 13.2 volts and does not climb above 13.5 volts during the flash process. An unstable voltage can interrupt or corrupt the update.
• Interrupted Flash: If the flash process is interrupted or aborted for any reason, it must be restarted from the beginning.
• Post-Flash Actions: After applying TSB 18-005-26 REV. A, it is not necessary to send DID-I or DID-A information.

Required Tools or Parts

Technicians will require a wiTECH or equivalent diagnostic scan tool to perform the diagnosis and the PCM reprogramming procedure outlined in this TSB.

What Owners Should Know

This software update is reimbursable under the provisions of the vehicle's warranty. If your 2021 Jeep Wrangler exhibits any of the symptoms or DTCs mentioned, it is recommended to visit an authorized Jeep dealership for diagnosis and the necessary PCM software update.

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Source: NHTSA ID: 11029673