B3935 on 2015-2022 Chevrolet Silverado 1500: Causes for Immobilizer No-Start

What's Unique About the 2015-2022 Chevrolet SILVERADO 1500

On these Silverado models and their platform-mates (GMC Sierra, Tahoe, Suburban), the immobilizer system is known to be sensitive. GM has issued multiple Technical Service Bulletins (TSBs) acknowledging that this code is frequently caused by Radio Frequency Interference (RFI) from a wide range of aftermarket devices like phone chargers, dash cams, aftermarket LED lights, or even RFID cards on the keychain. For 2014-2015 models specifically, a known software glitch in the Body Control Module (BCM) can also trigger this code, with the fix being a simple reprogram, not a part replacement.

Diagnostic Flowchart

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

Generation note: This issue affects both the third generation (K2XX; 2015-2019) and fourth generation (T1XX; 2019-2022) Silverado 1500. A BCM software update specifically addresses this code on 2014-2015 models (K2XX) per TSB PI1180A. The radio frequency interference issue is common to both generations, as noted in TSBs like PIC5650M which covers models up to 2022 and beyond. [Bulletin #PIC5650M]

Symptoms You May Notice

• Intermittent no-crank, no-start condition. [Bulletin #PIC5650M, #PIC5650L]
• Engine starts and immediately stalls.
• Security indicator light (a car with a lock symbol) is illuminated or flashing on the dashboard.
• "Service Theft Deterrent System" message may appear on the driver information center.
🎬 See this quick guide on resetting the anti-theft system.
• A "No Fob Detected" message may appear on keyless/passive start vehicles.

Most Likely Causes

1. Radio Frequency Interference (RFI) 🔴 High Probability The immobilizer system operates at 125 kHz and is sensitive to interference from aftermarket electronics that emit signals in a similar range. GM TSBs PIC5650L and PIC5650M specifically warn against replacing parts before checking for RFI from a long list of potential sources, including: phone chargers, dash cams, aftermarket LED lights (dome, headlights, etc.), toll passes, building access cards, and even decorative keyhole trim. [Bulletin #PIC5650L, #PIC5650M, 10]
   How to confirm: Unplug ALL aftermarket devices from 12V/USB ports. Remove any non-factory fobs, RFID cards (work badges, toll passes), and other electronics from the keychain and the vehicle's interior. Turn off any aftermarket lighting. Try to start the vehicle again. If it starts, reintroduce items one by one to find the culprit.
   Typical fix: Identify and remove the source of the interference. Relocate chargers or use higher quality, shielded electronics.
   Est. part cost: $0
2. Body Control Module (BCM) Software Update Needed 🟡 Medium Probability → Shop Body Control Module Specifically for 2014-2015 models (including Silverado, Sierra, Tahoe, Suburban, and Yukon), GM released TSB PI1180A to address a software issue where the BCM incorrectly reads the immobilizer information, causing a 'No Click, No Crank, No Start' condition with codes B3935 and B2955 set.
   How to confirm: A GM dealer or qualified shop with access to the Service Programming System (SPS) can check the current BCM calibration version against the latest release. The presence of both B3935 and B2955 is a strong indicator for this specific issue.
   Typical fix: Reprogram the BCM with the updated software calibration. This does not require replacing the module.
   Est. part cost: $0 (parts), $100-$200 (labor for programming)
3. Defective Key Transponder 🟡 Medium Probability The transponder chip embedded in the key head can fail internally from being dropped or from age. The rest of the key's functions (remote lock/unlock) may still work.
   How to confirm: Try starting the vehicle with a spare key. If the spare key works consistently, the original key is the problem. This is the first step recommended in service manuals before replacing modules.
   Typical fix: Replace the faulty key and have the new key programmed to the vehicle.
   Est. part cost: $75-$250
4. Weak Key Fob Battery ⚪ Low Probability → Shop Vehicle Battery While the transponder is passively powered by the ignition coil, a very weak fob battery can sometimes cause erratic communication issues with the vehicle's security systems. On push-to-start models, a weak battery can prevent the fob from being detected.
   How to confirm: Replace the battery inside the key fob (typically a CR2032 coin cell). This is a simple and inexpensive first step. If the vehicle has a key fob pocket/slot in the center console, placing the fob there may allow the vehicle to start even with a dead battery.
   Typical fix: Install a new key fob battery.
   Est. part cost: $2-$10

Rare But Worth Checking

• Faulty Theft Deterrent Module (TDM) or Antenna Ring: → Shop Anti-Theft Control Module This is rare. Service manuals and TSBs advise ruling out all other causes, especially RFI and key issues, before suspecting a module failure. TSB PIC5650L explicitly states not to replace any parts for this concern initially. [Bulletin #PIC5650L]
• Poor BCM Ground at G218: A GM TSB for various electrical issues, including no-start conditions, points to a poor BCM ground at location G218. This ground is located behind the driver's side kick panel/A-pillar trim. The dash insulation can get trapped under the ground stud, causing high resistance and a host of intermittent electrical problems.

Diagnosis Steps

1. Check for the security light on the dash. An illuminated light confirms a theft system issue.
2. Remove ALL aftermarket devices from the 12V/USB ports (phone chargers, dash cams, USB power banks, etc.).
3. Turn off all aftermarket LED lights.
4. Remove any other keys, fobs, or RFID cards (toll passes, work badges) from the keychain and from the vehicle's interior.
5. Attempt to start the vehicle. If it starts, one of the removed items was the cause.
6. If it still doesn't start, try your spare key. If the spare key works, the primary key is faulty.
7. Replace the battery in the key fob that is having issues.
8. If you have a push-to-start model, try placing the problematic fob in the designated transmitter pocket (check owner's manual for location, often in the center console) and attempt to start.
9. If none of the above steps work, the vehicle may need professional diagnosis. Mention the possibility of a BCM software update (TSB PI1180A) if you have a 2015 model, or the RFI issue (TSB PIC5650L/M) for all years.

Parts You'll Likely Need

• Ignition Key (OEM #ACDelco 22881480, 84540865 (FCC ID: M3N-32337100 for K2XX models)) — The transponder chip inside the key can fail, causing the authentication error. If a spare key works, the original key needs replacement.
  Trusted brands: ACDelco
  OEM price range: $100-$250
  Aftermarket price range: $75-$150
• Key Fob Battery (OEM #CR2032) — A weak battery is a simple, low-cost item to replace as a preliminary step before more complex diagnostics.
  Trusted brands: Duracell, Energizer
  OEM price range: $5-$10
  Aftermarket price range: $2-$5

Related Codes That Often Appear With This One

• B2955 — Specifically seen with B3935 on 2014-2015 models that require the BCM software update per TSB PI1180A.
• B3055 — Relates to a problem with the key transponder itself. Often set alongside B3935. 🎬 Watch: Step-by-step diagnosis for B3935 and related immobilizer codes. [Bulletin #PIC5650M, 10]
• B3060 — Indicates an issue with the transponder antenna circuit, often triggered by the same RFI that causes B3935. [Bulletin #PIC5650M, #PIC5650L, 10]

Technical Service Bulletins (TSBs) & Recalls

• PIC5650M: Intermittent no crank/no start/stall with security light on, advises checking for RFI.
• PIC5650L: Similar to the above, explicitly states not to replace parts and to ask about RFI sources.
• PI1180A: Intermittent No Start, Security Lamp Illuminated, DTCs B3935 and B2955 Set on 2014-2015 models, fixed by a BCM reprogram.

Platform-Specific Known Issues

• TSB PIC5650L/M: Warns of intermittent no-start or stall conditions with code B3935 due to Radio Frequency Identification interference. It explicitly advises against replacing parts and to investigate customer use of aftermarket electronic devices, including phone chargers, USB power banks, aftermarket LED lighting, and even RFID toll passes or access cards. [Bulletin #PIC5650L, #PIC5650M, 10]
• TSB PI1180A: Affects 2014-2015 models (Silverado, Sierra, Tahoe, Suburban, Yukon) where a no-start condition with codes B3935 and B2955 can be resolved by reprogramming the Body Control Module (BCM) with an updated software calibration.

Hidden / Shadow Codes Worth Checking

• B3935 57: The '57' is a symptom byte indicating 'Transponder Authentication Error'. This confirms the issue is with the challenge/response calculation between the key and the module, not a simple failure to read the key. (see via GM's GDS2 or a professional scan tool capable of reading manufacturer-specific symptom bytes.)

Scan Tool Commands That Help

• GDS2: Immobilizer Learn — Used after replacing the BCM or keys. This function guides the technician through the 10-minute or 30-minute relearn procedure to program new keys/modules to the vehicle.
• GDS2: Add/Replace Key Fobs — A specific function within the 'Remote Control Door Lock Receiver' module menu to program the remote functions (lock/unlock) of a new key fob.
• GDS2: BCM Reprogramming with SPS — Used to apply software updates, such as the one specified in TSB PI1180A for 2014-2015 models, which fixes the B3935/B2955 no-start condition. Requires an online connection to GM's Service Programming System (SPS).
• GDS2: Theft Data Display — When diagnosing a no-start, a technician can view live data from the Theft Deterrent Module (TDM) to see parameters like 'Vehicle Theft Turn Fuel Enabled' and 'CDT Status' to determine if the security system is commanding the no-start.

Wiring & Ground Locations

• G218 — On the driver's side, behind the A-pillar lower trim panel (kick panel), near the floor.. This is a major body ground point. TSB 18-NA-161 identifies a poor connection here (often due to dash insulation getting trapped under the stud) as a cause for various electrical issues, including battery drain and no-start conditions that can affect the BCM and theft deterrent system.
• Instrument Panel Fuse Block (Driver Side) — Behind a cover on the driver's side of the dashboard, accessible when the door is open.. Contains multiple fuses for the Body Control Module (BCM). For 2014-16 models, check fuses F6, F7, and F17. For 2017-19 models, also F6, F7, and F17. A loss of power here can cause the BCM to malfunction and set various codes, including B3935.
• Instrument Panel Fuse Block (Passenger Side) — Behind a cover on the passenger's side of the dashboard, accessible when the door is open.. Contains additional BCM fuses. For 2014-16 models, check fuses F7, F28, F45, and F46. For 2017-19 models, check F7, F8, F45, and F46. These fuses power different functions of the BCM.
• Low-Speed GM-LAN Bus — Pin 1 of the Data Link Connector (DLC) under the driver's dash. This circuit connects multiple modules, including the BCM and TDM, via splice packs like JX200 and JX300.. The TDM communicates with the ECM via this data bus. A short or open in this circuit can prevent the 'all clear' signal from reaching the ECM, resulting in a no-start and setting communication or module-specific codes. A short to voltage on this line can disable communication with all modules on the bus.

Real Owner Repair Stories

• YouTube user 'Hunter Wilson' (2014-2018 Chevrolet Silverado) — Complete electrical shutdown while driving or backing up, flickering dash lights, radio shutting off.
  ❌ Tried (didn't work) Initial diagnosis pointed to various potential electrical failures.
  ✅ What actually fixed it The problem was traced to a poor ground at G218, located behind the driver's side kick panel. The dash insulation material had gotten caught under the ground nut, preventing a solid connection. The fix was to remove the nut, trim away the interfering insulation, clean the contact surfaces, and retighten the ground nut. A secondary frame ground was also cleaned for good measure.
• Reddit user 'bbbbbraddddd' (2015 Silverado 1500 LT) — Stabilitrak service message, radio and A/C would randomly shut off and turn back on.
  ❌ Tried (didn't work) Owner was experiencing multiple intermittent electronic issues.
  ✅ What actually fixed it The owner identified a bad ground connection as the root cause. The post includes a video showing the location, consistent with the G218 ground, where sound-deadening insulation was interfering with the electrical contact point. Fixing the ground resolved all symptoms.

Model Year Variations Within This Range

• 2015-2019 (K2XX Platform): These models are part of the K2XX generation. They are specifically prone to the G218 ground issue behind the driver's kick panel and the BCM software glitch addressed by TSB PI1180A (for 2015 models).
• 2019-2022 (T1XX Platform): The 2019 model year marked the switch to the T1XX platform. While still susceptible to RFI issues per TSB PIC5650M, the electrical architecture, module locations, and fuse layouts differ from the K2XX trucks. For example, the fuse for the Theft Deterrent system in a 2019 model is listed in the Rear Seat Entertainment fuse location (F8 in the passenger side instrument panel fuse block).