B3935 on 2019-2024 Chevrolet Camaro: No-Start, Security Light Causes & Fixes

What's Unique About the 2019-2024 Chevrolet CAMARO

For this generation of Camaro, the security system can be particularly sensitive. General Motors has issued Technical Service Bulletins (TSBs), specifically the PIC5650 series, acknowledging that intermittent no-start conditions with code B3935 can be caused 🎬 Watch: A quick explanation of the B3935 fault code. by simple radio frequency interference (RFI). This means other RFID-enabled items like credit cards, work badges, another car's key fob on the same keychain, or even aftermarket electronics like phone chargers and LED lights can disrupt the 125 kHz signal between the key and the car, tricking the system into thinking there's a fault when no parts have actually failed.

Diagnostic Flowchart

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

Symptoms You May Notice

• Intermittent no-crank or no-start condition.
• Engine starts and immediately stalls.
• "Service Theft Deterrent System" message on the driver information center.
• Security indicator light is illuminated or flashing on the dashboard.
• "No Remote Detected" message on the driver information center, even with the key inside the car.

Most Likely Causes

1. Radio Frequency (RF) Interference 🔴 High Probability As noted in GM TSB #PIC5650M, the vehicle's security system is sensitive to external radio signals from devices like other key fobs, toll passes, access cards, and even aftermarket phone chargers or LED lights. This is the most likely cause for intermittent issues.
   How to confirm: Remove the Camaro key fob from your keychain so it is isolated from all other keys, fobs, and RFID-enabled cards (like credit cards or office access cards). Attempt to start the vehicle. If it starts consistently, interference was the cause. If it still fails, place the isolated fob in the rear cupholder (the designated transmitter pocket) and try again.
   Typical fix: Keep the Camaro key fob separate from other devices that may cause radio frequency interference. No parts replacement is necessary.
   Est. part cost: $0
2. Weak or Dead Key Fob Battery 🟡 Medium Probability
   How to confirm: Try using the vehicle's second key fob. If the second key works reliably, the battery in the first key is the likely culprit. You can also try placing the problematic fob in the designated transmitter pocket (the rear cupholder) which is designed to start the car with a weak or dead battery.
   Typical fix: Replace the battery inside the key fob (typically a CR2032 coin cell).
   Est. part cost: $2-$10
3. Faulty Key Fob Transponder ⚪ Low Probability
   How to confirm: If a new battery and eliminating RF interference doesn't solve the issue, and the second key works perfectly, the transponder chip in the first key has likely failed. A locksmith or dealer can test the key's signal. An owner on Camaro5 forums confirmed this was their issue, which was resolved with a new key and relearn procedure.
   Typical fix: The key fob must be replaced and programmed to the vehicle by a dealer or a qualified automotive locksmith.
   Est. part cost: $150-$400
4. Body Control Module (BCM) Software Glitch ⚪ Low Probability
   How to confirm: This requires a professional diagnosis. If the code B3935 is consistently present with B2955, and no key or interference issues are found, a software issue is possible. A dealer would check for the latest calibrations.
   Typical fix: A GM dealer needs to reprogram the BCM with the latest software calibration using the Service Programming System (SPS). Labor for a reflash is often around one hour, costing approximately $150-$250.
   Est. part cost: $0 (if covered by a campaign), otherwise labor cost for reprogramming.

Rare But Worth Checking

• Faulty Keyless Entry Control Module or Antenna: If none of the above solutions work and both keys fail to start the vehicle, the module that reads the key signal or its associated antenna may have failed. This requires advanced diagnostics with a professional scan tool to check communication and signal strength.
• Faulty Body Control Module (BCM): In rare cases, the BCM itself can fail internally. This is the most expensive repair, as the module itself can cost $300-$600 from a dealer, plus 1-2 hours of labor and mandatory programming. Aftermarket pre-programmed modules are a more affordable option.

Diagnosis Steps

1. Check for other Diagnostic Trouble Codes (DTCs) stored in the system.
2. Isolate the key fob from all other keys, fobs, and RFID cards. Remove it from the keychain and try starting the vehicle.
3. If you have a second key, try using it to see if the problem disappears.
4. Replace the battery in the key fob that is causing the issue (CR2032).
5. If the vehicle displays a 'No Remote Detected' message, place the fob flat in the rear cupholder in the center console (the transmitter pocket) and attempt to start the engine. This should work even with a dead fob battery.
6. Inspect the vehicle for aftermarket electronics that could cause RFI, such as phone chargers, dash cams, or LED lighting, and unplug them.
7. If the problem persists, the vehicle needs to be diagnosed by a professional with a scan tool capable of reading Body Control Module data to check key status and antenna function.
8. A technician will check for applicable TSBs, such as #PIC5650M and #PIC5650L, to see if the symptoms match a known issue with a specific fix like a BCM re-flash.

Parts You'll Likely Need

• Key Fob Battery (OEM #CR2032) — This is the most common and simple fix for a weak signal from the key fob, which can cause authentication errors.
  Trusted brands: Energizer, Duracell, Panasonic
  OEM price range: $5-$10
  Aftermarket price range: $2-$5
• Keyless Entry Transmitter (Key Fob) (OEM #13529660, 13529662, 13529653 (verify by VIN and button configuration)) — If the internal transponder chip fails, the entire key fob must be replaced and programmed to the vehicle. Part numbers vary based on features like convertible top controls.
  Trusted brands: ACDelco (OEM)
  OEM price range: $150-$300
  Aftermarket price range: $70-$150

Related Codes That Often Appear With This One

• B3055 — Relates to a problem with the key transponder itself. Often appears with B3935.
• B3060 — Indicates an issue with the transponder system's antenna or circuitry, which is directly related to reading the key.
• B2955 — This code for the Security Sensor Data Circuit often appears with B3935 when there is a BCM software issue requiring an update, as noted in GM service bulletins.
• C0750, C0755, C0760, C0765, C0775 — These codes are related to Tire Pressure Monitoring System (TPMS) sensors. TSB #PIC5650M notes they can appear alongside B3935, suggesting a broader communication or RF interference issue within the vehicle's systems, as TPMS also uses RF signals.

Technical Service Bulletins (TSBs) & Recalls

• PIC5650M: Addresses intermittent no-crank/no-start with security light and lists B3935 among other potential codes, pointing to RFI from aftermarket devices.
• PIC5650L: Specifically warns against replacing parts for B3935 and points to Radio Frequency Identification (RFID) interference as a primary cause.
• 21-NA-061: General information bulletin for dealers on diagnosing key fobs, reinforcing the use of specialized tools.

Platform-Specific Known Issues

• TSB #PIC5650L explicitly states that for intermittent no-start issues with code B3935, technicians should investigate RF interference from other devices on the customer's keychain before replacing any parts.
• TSB #PIC5650M links B3935 with a cluster of other security and sensor codes (B3055, B3060, C0750-C0775), indicating a potential for widespread RF communication disruption from sources like aftermarket LED lights or phone chargers.
• The designated transmitter pocket to bypass a dead key fob battery or interference is located in the rear cupholder of the center console for the 2016-2024 Camaro.

Mechanic-Grade Diagnostic Values

• Keyless Entry Antenna Signal Circuit Resistance to Ground — expected: Infinite resistance (OL). Failure: Any reading less than infinite resistance indicates a short to ground.
• Keyless Entry Antenna Signal Circuit End-to-End Resistance — expected: Less than 2 Ω. Failure: A reading of 2 Ω or greater indicates an open or high resistance in the circuit.
• Keyless Entry Antenna Low Reference Circuit Resistance to Ground — expected: Less than 30 Ω. Failure: A reading of 30 Ω or greater indicates a poor ground connection.

Hidden / Shadow Codes Worth Checking

• B3935 57: Transponder Authentication Error. This is the most common symptom byte associated with B3935, indicating the BCM recognized a valid key but the cryptographic challenge-response failed. (see via A professional scan tool like the GM Tech2 or GDS2 is required to read symptom bytes.)
• B3935 71: Invalid Key. This symptom byte indicates that the transponder data received is not from a key that is learned to the vehicle. (see via A professional scan tool like the GM Tech2 or GDS2 is required to read symptom bytes.)

Scan Tool Commands That Help

• GDS2/Tech2: Immobilizer Learn / Key Learn — This function is required after replacing a key fob or the Body Control Module (BCM). It guides the technician through the process of programming new keys to the vehicle's immobilizer system.
• GDS2/Tech2: Body Control Module (BCM) Programming and Setup — Used when a BCM is replaced or if a software update (reflash) is required to fix a known bug, such as the one mentioned in bulletin PI1180A for B3935 with B2955.

Wiring & Ground Locations

• K17 Keyless Entry Control Module (KEM) — Located in the trunk area, on the driver's side (LH) rear wheel well, behind the trunk trim panel. It is often stacked with other modules like the fuel pump controller.. This module is the central brain for the keyless entry and passive start system. It communicates with the key fob, the BCM, and the various antennas. A loose connection or fault in this module can directly cause B3935.
• K9 Body Control Module (BCM) — For the 6th Gen Camaro, the primary BCM is located behind the fuse panel in the passenger side of the center console. Another source places it behind the left side of the dash.. The BCM is the final authority for immobilizer authentication. It receives the signal from the KEM and makes the decision to allow the car to start. Software glitches or internal faults in the BCM can set this code.
• Keyless Entry Antennas — There are multiple low-frequency antennas: one in the center of the dash (behind the HVAC controls), one in the rear of the center console, one in the trunk near the seatbacks, and one under the rear bumper.. These antennas are what receive the signal from the key fob. A failure or short in one of these antennas or their wiring can prevent the KEM from reading the key, leading to an authentication error.

Real Owner Repair Stories

• Camaro6 Forum user 'squish72' (2019 Camaro) — Intermittent no-start, "Service Keyless Start System" message. Scan tool revealed code B3122 (keyless entry antenna 4 short/open), which is related to the same system as B3935.
  ❌ Tried (didn't work) Replacing key fob battery, Checking fuses
  ✅ What actually fixed it The owner located the Keyless Entry Module in the rear driver's side quarter panel in the trunk. After disconnecting and reconnecting the two plugs on the module, the system began working correctly, suggesting a poor connection at the module was the root cause.
• Camaro5 Forum user 'RedTexasSS' (2012 Camaro SS) — No crank, "Service Theft Deterrent System" message. A Snap-on scanner found code B3935, Transponder Authentication Error.
  ❌ Tried (didn't work) Checking fuses, Checking battery connections, Attempting a 3x10 minute key relearn procedure that failed.
  ✅ What actually fixed it The original key fob's transponder had failed. A locksmith cut a new, simple key, and a successful 30-minute relearn procedure (3 cycles of key-on for 10 minutes until the security light goes out) allowed the car to start. A new switchblade key was then purchased and programmed.

OEM Part Supersession History

• 13508771, 13584504 → 13529660 — Standard part revision and consolidation for the Keyless Entry Transmitter (Key Fob).
  Heads up: The new part number requires programming by a dealer or qualified locksmith with access to GM's Service Programming System (SPS).
• 13592451 → 13546098 — Updated part for the various Keyless Entry Antennas used throughout the vehicle.