P0513 on 2018-2025 Cadillac XT5: 'Incorrect Immobilizer Key' Causes and Fixes

What's Unique About the 2018-2025 Cadillac XT5

For this generation of Cadillac XT5 and related GM C1XX platform vehicles, P0513 is specifically addressed by Technical Service Bulletin 🎬 Watch: A short explanation of the Cadillac P0513 code. #23-NA-165. The TSB indicates that a memory corruption event can occur in the Body Control Module (BCM), especially after a low voltage situation like a jump start or battery replacement. This makes the issue less about a faulty key and more about a sensitive control module that may require a specific software update from the dealer to resolve the no-start condition. The TSB explicitly warns technicians not to replace modules before performing the software update.

Diagnostic Flowchart

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

Symptoms You May Notice

• Engine will not crank or start.
• Keyless entry functions (lock/unlock) do not work.
• Message on the dash such as "No Remote Detected" or "Place Key In Transmitter Pocket".
• Illuminated security light on the instrument panel (may be a key symbol or a padlock).
• Engine may start and then immediately stall (less common for this specific TSB issue).

Most Likely Causes

1. Body Control Module (BCM) Memory Corruption 🔴 High Probability → Shop Body Control Module As per TSB #23-NA-165, these vehicles can experience a BCM memory corruption event after a low voltage condition (e.g., jump start, battery replacement), causing it to lose recognition of valid keys. This affects vehicles with the GEN3R BCM.
   How to confirm: A GM dealer must use a proprietary scan tool (GDS2) to check for this condition and determine if the BCM software needs updating per the TSB. The bulletin specifically instructs technicians to check for P0513 and not to attempt standard immobilizer relearns before applying the software fix.
   Typical fix: The dealer performs a specific BCM programming and immobilizer relearn procedure outlined in TSB #23-NA-165. This involves using the Service Programming System (SPS) to apply a software update.
   Est. part cost: $0
2. Weak or Dead Key Fob Battery 🟡 Medium Probability → Shop Vehicle Battery This is a common issue for all vehicles with keyless start. The fob's signal becomes too weak for the car's antenna to receive.
   How to confirm: Try starting the vehicle by placing the key fob in the transmitter pocket located in the front of the center console, inside the main storage area; this allows the car to start even with a dead fob battery. Alternatively, try using the spare key. If the spare key works, the issue is with the primary key fob.
   Typical fix: Replace the CR2032 battery in the key fob.
   Est. part cost: $2-$10
3. Faulty Key Fob ⚪ Low Probability → Shop Keyless Entry Transmitter Key fobs can fail from being dropped, water damage, or internal electronic failure. The internal transponder chip can be damaged even if the lock/unlock buttons still function.
   How to confirm: If a new battery doesn't fix the issue and the spare key works perfectly, the original key fob is likely defective. A locksmith or dealer can test the fob's signal.
   Typical fix: Replace the key fob and have it professionally programmed by a dealer or qualified automotive locksmith.
   Est. part cost: $150-$400

Rare But Worth Checking

• Faulty Immobilizer Antenna: → Shop Antenna The antenna ring (also called a coil) around the ignition or start button reads the key's signal. If it fails, it cannot detect a valid key, even if the key is good.
• Poor Electrical Connection or Ground: On other GM platforms, similar symptoms have been traced to corroded wiring or poor ground connections for the BCM. While the TSB is more likely for the XT5, a visual inspection of the BCM wiring harness and ground points is a valid diagnostic step, especially if U-codes are also present.

Diagnosis Steps

1. Attempt to start the vehicle by placing the key fob in the designated transmitter pocket in the center console. If it starts, replace the key fob battery.
2. If you have a spare key, try using it. If the spare key works, the problem is isolated to the first key fob (either its battery or the fob itself).
3. Replace the CR2032 battery in the non-working key fob.
4. Check for any messages on the Driver Information Center (DIC), such as "No Remote Detected".
5. If the vehicle still won't start with a new battery or the spare key, the issue is likely with the vehicle's control modules, especially if the problem appeared after a battery replacement or jump-start.
6. The vehicle must be taken to a Cadillac dealer or a qualified shop with GM diagnostic tools.
7. A technician will scan for codes and reference TSB #23-NA-165, which details a specific BCM reprogramming and immobilizer relearn procedure to resolve the issue. They will use GDS2 to confirm the vehicle has a GEN3R BCM, which is eligible for this TSB.

Parts You'll Likely Need

• Key Fob Battery (OEM #CR2032) — This is the most common and simplest fix when the key fob signal is weak.
  Trusted brands: Energizer, Duracell, Sony
  OEM price range: $5-$10
  Aftermarket price range: $2-$8
• Keyless Entry Remote Fob (OEM #13510245, 13598516 (Verify by VIN)) — Required if the key fob's internal electronics have failed. Must be programmed to the vehicle.
  Trusted brands: ACDelco (OEM)
  OEM price range: $200-$400
  Aftermarket price range: $75-$200

Technical Service Bulletins (TSBs) & Recalls

• 23-NA-165: Vehicle Will Not Lock and Unlock (Loss of Active Functions) Crank or Start (Loss of Passive Functions) with DTC P0513 Set. This bulletin provides the specific diagnostic and programming steps to correct a BCM memory corruption issue. It applies to vehicles with a GEN3R BCM.
• 21-NA-277: An earlier TSB that also addressed P0513 on similar platforms, highlighting that this has been a known issue pattern for GM.

Platform-Specific Known Issues

• TSB #23-NA-165 directly addresses an issue where the Cadillac XT5 may not lock, unlock, crank, or start, with DTC P0513 set. The cause is identified as a potential memory corruption event in the Body Control Module (BCM), often triggered by a low voltage event like a battery replacement or jump-start. The fix is a specific dealer-performed software update and immobilizer relearn.

Hidden / Shadow Codes Worth Checking

• B389A 00: Indicates an issue with immobilizer key programming or module setup. TSB 21-NA-277 advises that if this code is not present with P0513, to disconnect/reconnect the battery for 30 seconds and recheck for it. (see via GM GDS2 or equivalent professional scan tool.)
• B3924 00, B3925 00, B3926 00, B3927 00: These are 'Environment ID' DTCs that can be set in the BCM along with P0513, indicating a module configuration mismatch, often after a low-voltage event. (see via GM GDS2 or equivalent professional scan tool.)
• B3935 57: Indicates a 'Transponder Authentication Error' with a specific symptom byte '57' meaning the key's security calculation did not match the BCM's expected value. This points to a data mismatch rather than a total signal loss. (see via GM GDS2 or professional scan tool capable of reading manufacturer symptom bytes.)

Scan Tool Commands That Help

• GDS2 (Service Programming System - SPS): Immobilizer Learn: Replacement BCM with existing transmitter fobs — This specific function is used after BCM reprogramming as per TSB 21-NA-277 to relearn the original keys without needing to replace them.
• GDS2 (Service Programming System - SPS): BCM Setup — This is a required final step after BCM programming and the immobilizer learn procedure to configure the BCM to the vehicle's specific options and ensure all systems function correctly.
• GDS2 (Service Programming System - SPS): Program Transponder or Remote Key (Add) — Used to add a new key to the system or to attempt to relearn a key that is no longer being recognized by the BCM.

Wiring & Ground Locations

• K9 Body Control Module (BCM) — Inside the passenger cabin, located under the dashboard on the driver's side, near the A-pillar or kick panel area.. The BCM is the central computer for the immobilizer system. It receives the key's signal, validates it, and sends the enable signal to the PCM. All related wiring and grounds terminate here.
• G218 — A primary BCM ground point located behind the driver's side A-pillar trim or kick panel, near the BCM itself.. A GM Technical Service Bulletin (PIT5405C) directly links a poor connection at G218 to a no-start condition with DTC P0513. The bulletin notes the dash insulation mat can get trapped under the ground nut, causing high resistance. This is a critical, non-obvious failure point.
• Immobilizer Antenna / Transmitter Pocket — The backup antenna is located inside the center console storage area, in a dedicated slot or pocket designed to hold the key fob.. This is the designated location to place the key fob to start the vehicle when the fob's battery is dead. It allows the low-power transponder chip to be read directly by a dedicated antenna.

Real Owner Repair Stories

• Reddit user post in r/Cadillac (2018 Cadillac XT5) — Vehicle would not recognize the second key fob, even after a battery change. Attempting the owner's manual key programming procedure resulted in erasing the working key and the vehicle being unable to learn any keys, new or old.
  ❌ Tried (didn't work) Replacing the battery in the non-working key fob., Performing the '30-minute relearn procedure' as described in the owner's manual., Attempting to program a new aftermarket key fob using the same manual procedure.
  ✅ What actually fixed it The vehicle had to be taken to the dealership. The dealer's service department used their proprietary scan tool (GDS2) and software to successfully program the keys. The owner's manual procedure was insufficient and led to a total lockout.

OEM Part Supersession History

• 13510245, 13598516 (FCC ID: HYQ2EB) → N/A - Applies to specific model years — Original part for pre-refresh models.
  Heads up: This key fob is for 2017-2020 models and is NOT compatible with 2020.5+ models that use the Global B electrical architecture.
• 13522879, 13544052 (FCC ID: HYQ2ES) → N/A - Applies to specific model years — New part for post-refresh models with the Global B / VIP architecture.
  Heads up: This key fob is for 2020-2025 models and is NOT compatible with pre-2020 models.

Model Year Variations Within This Range

• 2020-2025: Starting with the 2020 model year refresh, the XT5 platform transitioned to GM's new Global B electrical architecture (Vehicle Intelligence Platform). This involves a more complex and secure BCM and requires different key fobs (FCC ID: HYQ2ES). Programming or replacing the BCM on these newer models must be done with GM's latest Techline Connect (SPS2) software.