P0513 on 2018-2019 Fiat 500: Invalid Key Causes and Fixes

What's Unique About the 2018-2019 Fiat 500

For this generation of Fiat 500 and its platform mates (like the Jeep Renegade and Fiat 500X), the immobilizer system is highly sensitive to electronic disruptions. A key issue, highlighted by manufacturer Technical Service Bulletin (TSB) S2208000073, is that the P0513 code can be triggered after the vehicle's main computer (PCM) has been reprogrammed (flashed) or replaced. This indicates that the key data can be lost or corrupted during other unrelated service procedures. Furthermore, a significant voltage drop from a dead or disconnected main vehicle battery can also corrupt the security data in the PCM or BCM, leading to a surprise no-start condition even with a valid key.

Diagnostic Flowchart

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

Symptoms You May Notice

• Engine cranks but will not start.
• Engine may start and then immediately stall.
• Flashing security light on the instrument panel (often looks like a key or a lock).
• Check Engine Light is on.
• "Key not detected" message on the instrument cluster.

Most Likely Causes

1. Faulty or Unprogrammed Ignition Key 🔴 High Probability Keys can be damaged by being dropped or getting wet, and non-OEM replacement keys may have compatibility issues. A dead or weak CR2032 battery in the key fob can also prevent the signal from being sent.
   How to confirm: Try starting the vehicle with a known-good spare key. If the spare key works, the problem is with the primary key. A simple and inexpensive first step is to replace the CR2032 battery in the key fob. 🎬 Watch: How to replace your Fiat 500 key fob battery.
   Typical fix: If the battery is the issue, replace it. If the key's internal transponder has failed or lost its programming, the key must be replaced and programmed to the vehicle by a dealer or qualified locksmith with access to FCA's systems.
   Est. part cost: $5-$15 for a battery, $250-$500 for a new key and programming from a dealer.
2. Lost Key Programming due to PCM Flash/Replacement or Battery Drain 🟡 Medium Probability As documented in TSB #S2208000073, replacing or reprogramming the Powertrain Control Module (PCM) can cause it to lose synchronization with the existing keys, triggering a P0513 code. This is also extremely common after the main vehicle battery goes completely dead, causing data corruption in the security modules (PCM/BCM).
   How to confirm: This cause is highly likely if the P0513 code appeared immediately after the PCM was serviced, the main vehicle battery was replaced, or the vehicle was jump-started. A full system scan may show a U0426 code (Invalid Data From Immobilizer) in other modules.
   Typical fix: The keys must be re-synchronized with the PCM and the immobilizer module using a dealer-level scan tool (like WiTech). A 'Proxy Alignment' procedure is often required to make all vehicle modules recognize each other again. 🎬 See how a professional Proxi Alignment procedure is performed. In severe cases of data corruption, the PCM may need to be 'virginized' and reprogrammed by a specialist.
   Est. part cost: $0 in parts, but labor for reprogramming will apply, typically 1-2 hours.
3. Faulty Radio Frequency Hub (RF Hub) / Immobilizer Module ⚪ Low Probability The RF Hub (also called the SKIM or Wireless Ignition Node) is the component that reads the key's signal. Like any electronic module, it can fail internally or suffer from poor connections. On some Fiat/Chrysler platform mates, this module is located behind the rear seat or in the trunk.
   How to confirm: A professional scan tool is needed to check for communication with the RF Hub. If the module is unresponsive, has internal fault codes, or fails a self-test, it is likely faulty.
   Typical fix: The RF Hub module must be replaced and programmed to the vehicle's VIN and keys. This requires a dealer or specialist with online access to FCA security systems.
   Est. part cost: $150-$300 for the module, plus programming labor.
4. Wiring or Antenna Ring Issue ⚪ Low Probability The antenna ring around the ignition switch (or in the center console for keyless go models) picks up the key's signal. Damage to this ring or its wiring can prevent the signal from reaching the RF Hub module.
   How to confirm: Visually inspect the wiring around the ignition cylinder or center console for damage. A mechanic can test the continuity of the antenna coil with a multimeter; an open circuit indicates failure.
   Typical fix: Repair the damaged wiring or replace the antenna ring.
   Est. part cost: $50-$150 for the antenna ring.

Rare But Worth Checking

• Faulty Body Control Module (BCM):

Diagnosis Steps

1. Check the battery in the key fob (typically a CR2032) and replace if it's weak or old.
2. Attempt to start the car with a known-good spare key. If it starts, the first key is the problem.
3. Observe the dashboard for a flashing security light, which confirms an immobilizer issue.
4. If the issue occurred after a PCM replacement, software update, or dead vehicle battery, suspect a module synchronization issue as described in TSB #S2208000073.
5. Scan the vehicle with a high-level OBD-II scanner (like AlfaOBD or wiTECH) capable of reading security system codes from the PCM, BCM, and RF Hub.
6. Check for communication with the RF Hub/Immobilizer module. Note any specific fault codes stored in that module.
7. Inspect the wiring and connectors at the ignition switch antenna ring and the RF Hub module for any visible damage or corrosion.
8. If key programming is attempted and fails, suspect a deeper issue like a faulty BCM or corrupted PCM data requiring specialist intervention.
9. Perform a 'Proxy Alignment' procedure with a capable scan tool to ensure all modules on the CAN bus network are communicating correctly.

Parts You'll Likely Need

• Transponder Key Fob (OEM #68191237AC (supersedes 68191237AA, 68191237AB) or 68238593AA) — The transponder chip inside the key is the most common point of failure, either through damage, battery death, or losing its programming.
  Trusted brands: Mopar (OEM)
  OEM price range: $200-$350
  Aftermarket price range: $75-$150
• Radio Frequency Hub (RF Hub) / Immobilizer Module (OEM #68638464AA (for platform mate 500X, may vary for 500)) — This module reads the key signal. If it fails, no key will be recognized. Replacement requires professional programming.
  Trusted brands: Mopar (OEM)
  OEM price range: $150-$300
• Key Fob Battery (OEM #CR2032) — This is the most common and cheapest potential fix. A weak battery can fail to power the transponder chip correctly.
  Trusted brands: Duracell, Energizer
  OEM price range: $5-$10
  Aftermarket price range: $2-$5

Related Codes That Often Appear With This One

• U0426 - Invalid Data Received From Vehicle Immobilizer Control Module

Technical Service Bulletins (TSBs) & Recalls

• S2208000073: No Start, After Flash And Or PCM Replace, DTC P0513 Invalid Skim Key Setting

Platform-Specific Known Issues

• A known issue documented in TSB #S2208000073 involves this code appearing after a PCM replacement or software flash, causing a no-start situation due to lost key synchronization.
• These vehicles are known to be sensitive to low voltage from the main battery, which can corrupt security data in the PCM or BCM, leading to P0513 without any parts actually failing.

Mechanic-Grade Diagnostic Values

• Immobilizer Antenna Ring Continuity — expected: The coil should show continuity (a low resistance reading, not an open circuit).. Failure: An 'OL' (Over Limit) or infinite resistance reading on a multimeter indicates the coil inside the antenna ring is broken.

Scan Tool Commands That Help

• wiTECH, AlfaOBD, Autel: Proxy Configuration Alignment (Proxi Alignment) — This is the most critical function for this platform. It must be run after replacing a major module (BCM, PCM, RF Hub) or after a data corruption event (e.g., dead battery) to force all modules on the CAN network to re-synchronize their configuration and security data.
• wiTECH, AlfaOBD: PCM Replaced — As specified by TSB S2208000073, this routine must be run when the PCM is replaced or reflashed. It re-establishes the security handshake between the BCM, RF Hub, and the new/updated PCM.
• Autel MaxiIM, Smart Pro, etc.: Key Programming / Learning — Used to add new keys or re-learn existing keys. For Fiat, this requires obtaining the vehicle's 5-digit security PIN and often involves a 'pre-coding' step where the new key is prepared with vehicle-specific data before it can be learned by the car.
• Autel MaxiIM: Write new BCM data to ECU — An advanced function used after a BCM swap to force the original ECU to accept the new module. This may fail if the ECU is not in a 'virgin' (factory reset) state, indicating that the ECU itself may need to be reset by a specialist before it will pair with a different BCM.

Wiring & Ground Locations

• Body Control Module (BCM) — Located in the driver's side footwell, behind the plastic trim panel to the left of the brake pedal and above the OBD-II port.. The BCM is the central gateway for the immobilizer system. All security communications pass through it. A loose connector or fault at the BCM can cause a total communication breakdown and trigger P0513.
• Main Chassis/Engine Ground Strap — Underneath the battery and battery tray. One end connects to the chassis near the battery, and the other connects to the transmission case.. This strap is notorious for corrosion on Fiat 500s. A poor ground can cause unstable voltage and electrical noise throughout the vehicle, disrupting communication between the BCM, PCM, and RF Hub, leading to intermittent or persistent P0513 codes even when all modules are good.
• Radio Frequency Hub (RF Hub) — On platform mates like the Fiat 500X and Jeep Renegade, this module is located in the rear of the vehicle, often behind the rear seat or under the package tray. Its exact location on the 500 may vary but is separate from the BCM.. This is the module that directly receives the signal from the key fob's transponder. A loose connection or failure of this specific module will prevent any key from being recognized.

Real Owner Repair Stories

• MHH AUTO Forum (2013 Fiat 500 (similar immobilizer architecture)) — Car would not start and set code P0513 after swapping the Body Control Module (BCM).
  ❌ Tried (didn't work) Programming new keys using an Autel MaxiIM IM508. The tool reported 'success,' but the car still wouldn't start., Performing a 'Proxy Alignment' with AlfaOBD. The procedure completed, but the P0513 code immediately returned., Manually writing the correct VIN to the Engine Control Unit (ECU) using AlfaOBD.
  ✅ What actually fixed it The underlying issue was that the original ECU would not accept the security data from the replacement BCM. The scan tool's 'key programming success' message was misleading. The proposed and correct fix in this scenario is to have the original ECU sent to a specialist to be put into a 'virgin' state (factory reset). Only then can it be properly paired with the replacement BCM and keys via a proxy alignment.