2021-2025 Jeep, Fiat, Alfa Romeo Erroneous CEL DTCs

The Stellantis Technical Service Bulletin (TSB) 18-028-25, titled "Check Engine Light Illuminated - Erroneous Fault Codes Set," addresses a specific issue affecting various 2021-2025 Jeep, Fiat, and Alfa Romeo models. This bulletin is crucial for owners experiencing a Malfunction Indicator Lamp (MIL) illumination without an actual underlying component failure. The TSB highlights that certain diagnostic trouble codes (DTCs) may be set erroneously due to random false readings from the intake pressure and temperature sensors.

This issue specifically impacts vehicles equipped with the 1.3L I4 Turbo MAir DI Engine w/ESS (Sales Code EYF) or the 1.3L I4 Turbo PHEV Engine (Sales Code EYG). If you own a 2021-2025 Jeep Renegade, Fiat 500X, Jeep Compass, or Alfa Romeo Tonale and your Check Engine Light is on, this information is highly relevant.

Symptoms

Owners of affected vehicles will primarily notice the Malfunction Indicator Lamp (MIL), commonly known as the Check Engine Light, illuminated on their dashboard. Upon further investigation by a technician, one or more of the following Diagnostic Trouble Codes (DTCs) will likely be found stored in the Powertrain Control Module (PCM) or Engine Control Unit (ECU):

• P012C: Turbocharger/Supercharger Inlet Air Pressure Sensor 1 Circuit Low
• P012D: Turbocharger/Supercharger Inlet Air Pressure Sensor 1 Circuit High
• P006C-MAP: Turbocharger Inlet Air Pressure Correlation

These codes indicate an issue with the inlet air pressure sensor or its correlation with the Manifold Absolute Pressure (MAP) sensor. However, as the TSB explains, these codes may not always signify a true component fault.

Fault Codes / DTCs

The following Diagnostic Trouble Codes are specifically mentioned in TSB 18-028-25 as potentially setting erroneously:

Code	Description	Module
P012C	Turbocharger/Supercharger Inlet Air Pressure Sensor 1 Circuit Low	PCM/ECU
P012D	Turbocharger/Supercharger Inlet Air Pressure Sensor 1 Circuit High	PCM/ECU
P006C-MAP	Turbocharger Inlet Air Pressure Correlation	PCM/ECU

These codes are critical for diagnosing the issue, but it's important to understand their context as described in this bulletin.

Cause of the Erroneous CEL DTCs

The root cause for the "Check Engine Light Illuminated - Erroneous Fault Codes Set" condition is identified as a random false reading of the intake pressure and temperature. This means that the vehicle's Powertrain Control Module (PCM) or Engine Control Unit (ECU) is receiving incorrect data from the sensors, leading it to falsely believe there is a problem and trigger the Malfunction Indicator Lamp and store the associated DTCs. This is why a Jeep Renegade erroneous CEL DTCs might appear without an actual mechanical failure.

Important Warnings for Owners and Technicians

This Technical Service Bulletin 18-028-25 includes critical instructions to prevent unnecessary repairs and part replacements.

• DO NOT replace the IAP sensor or the MAP sensor. The bulletin explicitly states that replacing these sensors will not resolve the issue if the problem is due to erroneous readings rather than a faulty sensor.
• DO NOT PERFORM OTHER OPERATIONS OR REPLACE ANY PARTS. If, after following the prescribed diagnostic steps, no wiring issues are found and the DTCs do not reset after a test drive, no further action or part replacement is necessary. This prevents owners from incurring costs for parts that are not actually defective.

These warnings are crucial for ensuring that vehicles are repaired correctly and efficiently, avoiding costly and ineffective part replacements.

Diagnosis and Repair Summary

For vehicles exhibiting the Malfunction Indicator Lamp illumination and storing the erroneous DTCs, technicians are instructed to follow a specific diagnostic and repair procedure:

1. Save the Vehicle Scan Report: Before any work begins, a complete scan report of the vehicle's systems should be saved. This documents the initial state and confirms the presence of the specific DTCs.
2. Inspect Electrical Connections: The primary focus of the inspection should be on the electrical connections for both the Idle Air Pressure (IAP) sensor and the Manifold Absolute Pressure (MAP) sensor. Technicians should look for any signs of damage, corrosion, or looseness in the wiring.
3. Repair Wiring Issues: If any wiring issues are identified during the inspection, they should be repaired or corrected as necessary. This is the only repair action recommended if a physical fault is found.
4. Erase DTCs and Test Drive: If no wiring issues are found, the stored DTCs should be erased from the PCM/ECU. Following this, a test drive must be performed to determine if the erroneous CEL DTCs reappear.
5. Return Vehicle to Customer: If, after the test drive, none of the specific DTCs (P012C, P012D, P006C-MAP) reset, the vehicle should be returned to the customer. No further operations or part replacements are required. This confirms that the issue was indeed an erroneous reading.

This procedure ensures that the actual cause of the Jeep Renegade erroneous CEL DTCs is properly identified and addressed, without resorting to unnecessary component replacements.

Owner Action

If you own a 2021-2025 Jeep Renegade, Fiat 500X, Jeep Compass, or Alfa Romeo Tonale and your Check Engine Light is illuminated with any of the DTCs P012C, P012D, or P006C-MAP, it is recommended to schedule an appointment with your authorized Stellantis dealership. Inform them about the illuminated Malfunction Indicator Lamp and mention the possibility of erroneous fault codes as described in TSB 18-028-25. This TSB is for "Information Only," meaning it provides guidance to technicians on how to correctly diagnose and address the issue without necessarily being a full-blown recall or warranty repair campaign. However, proper diagnosis can prevent unnecessary costs.

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Source: NHTSA ID: 11019436