B3055 on 2017-2021 Gmc SAVANA: No Start, Security Light Causes and Fixes

What's Unique About the 2017-2021 Gmc SAVANA

The GMC Savana and its sibling, the Chevrolet Express, have used a similar, robust, but sometimes finicky Passkey III+ immobilizer system for many years. While the core technology is common across GM, these GMT610 platform vans are known for having Body Control Modules (BCM) that can be a point of failure for various electrical systems, including the anti-theft system. Unlike cars with push-button start, this traditional key-and-cylinder setup is straightforward but its components (key chip, exciter coil) are prone to wear, electronic failure, or interference over a long service life, especially in commercial-use vehicles.

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
• Engine starts briefly then immediately shuts off
• Security light (a car icon with a lock) is illuminated or flashing on the instrument cluster
• Message on the driver information center (if equipped) like 'Service Theft Deterrent System'

Most Likely Causes

1. Defective Ignition Key 🔴 High Probability → Shop Ignition Switch Keys are subject to physical damage from being dropped, getting wet, or simple electronic failure of the internal transponder chip over time. The flip-key style can also cause issues if not fully extended.
   How to confirm: Try starting the vehicle with a spare key. If the spare key works reliably, the original key is faulty. A locksmith or dealer can also test the key's transponder signal. A scan tool will show the key status as 'Not Present' when the bad key is used.
   Typical fix: Replace the faulty key. A new key must be cut and then programmed to the vehicle. This can be done by a locksmith/dealer or sometimes via the 30-minute relearn procedure.
   Est. part cost: $50-$150
2. Faulty Ignition Lock Cylinder Housing / Exciter Coil 🟡 Medium Probability → Shop Ignition Switch The exciter coil (antenna) that reads the key's transponder is built into the ignition lock cylinder housing. This component can fail electronically, creating an open or short in the circuit, preventing it from energizing the key chip.
   How to confirm: After confirming keys are good, a technician will test the resistance and signal wires between the lock cylinder housing and the BCM. If the wiring is good, the housing is the likely culprit. This is a common failure point if all keys fail to work.
   Typical fix: Replace the ignition lock cylinder housing. This part contains the immobilizer reader coil. After replacement, the 30-minute key relearn procedure is typically required. 🎬 Watch: A professional guide to the GM Passkey relearn procedure.
   Est. part cost: $70-$150
3. Radio Frequency (RF) Interference ⚪ Low Probability This is not vehicle-specific but a common issue with immobilizer systems. Other electronic devices on the same keychain (like another car's fob) or even phone chargers near the ignition can disrupt the low-frequency signal between the key and the vehicle.
   How to confirm: Remove all other keys, fobs, and electronic devices from the keychain and away from the ignition area. Try to start the vehicle with only the single Savana key. If it starts, interference was the issue.
   Typical fix: Keep other RFID-blocking cards, key fobs from other vehicles, and other electronics separate from the ignition key.
   Est. part cost: $0
4. Faulty Body Control Module (BCM) ⚪ Low Probability → Shop Body Control Module The BCM on Savana/Express vans is a known potential failure point for several electrical issues. While not the most common cause for B3055 specifically, it is a possibility if other symptoms like turn signal, lighting, or power lock issues are also present. Water intrusion can also damage the BCM.
   How to confirm: This is a diagnosis of exclusion. If the keys, ignition lock housing, and wiring have all been tested and are confirmed to be good, the BCM is the remaining likely cause. A full diagnostic scan of the BCM is required. TSB PIC5650M advises checking all other possibilities before condemning the BCM.
   Typical fix: Replace the Body Control Module. The new BCM must be programmed to the vehicle using dealer-level software (GM Techline Connect) or a specialized cloning service.
   Est. part cost: $250-$400

Rare But Worth Checking

• Wiring Harness Damage: Damage to the wires between the ignition lock cylinder and the BCM can cause this code. This is more common on work vans where aftermarket equipment (alarms, remote start, radios) may have been installed, potentially damaging factory wiring.
• Low Battery Voltage: → Shop Vehicle Battery A weak or failing battery can cause a multitude of erratic electronic issues, including causing the BCM or immobilizer system to malfunction and incorrectly set a B3055 code. Always ensure the battery is fully charged and healthy before diagnosing complex electronic faults.

Diagnosis Steps

1. Check for RF interference. Remove all other items from the keychain and try starting the vehicle with only the ignition key.
2. Try a spare key. If the vehicle starts and runs with the spare, the primary key is faulty.
3. Inspect the key for any visible damage. If using a flip-key style, ensure it is fully extended and locked straight, as a partially folded key can cause this code.
4. Connect a professional scan tool capable of reading BCM/TDM data. Check for B3055 and any other related security codes.
5. Use the scan tool to monitor the 'Transponder Key' status. Verify if the module sees the key as 'Present' or 'Not Present' when the key is in the ignition.
6. If keys and RF interference are ruled out, attempt the '30-Minute Relearn Procedure': Insert a new or existing key, turn to ON (not start). The security light will stay on. Wait ~10 minutes for it to turn off. Turn the key OFF for 5 seconds. Repeat this process two more times (3 cycles total). After the third cycle, turn the key off, then try to start the engine.
🎬 See this quick walkthrough of the 30-minute key relearn process.
7. If the relearn fails, inspect the wiring and connector at the ignition lock cylinder housing for damage or corrosion.
8. Test the resistance of the exciter coil and check for continuity on the signal and power wires between the lock cylinder housing and the BCM.
9. If wiring and the lock cylinder housing test good, the fault likely lies within the Body Control Module (BCM) itself.

Parts You'll Likely Need

• Transponder Ignition Key (OEM #23300334) — The transponder chip inside the key is the most common point of failure in the immobilizer system.
  Trusted brands: ACDelco (GM Genuine), Strattec (5928275)
  OEM price range: $70-$120
  Aftermarket price range: $40-$80
• Ignition Lock Cylinder Housing (OEM #23122150) — This part contains the antenna (exciter coil) that reads the key. If the coil fails, the key cannot be detected. This is a common repair for a 'no transponder' fault.
  Trusted brands: ACDelco (GM Genuine), Dorman
  OEM price range: $100-$180
  Aftermarket price range: $60-$120
• Body Control Module (BCM) (OEM #84922494) — The BCM is the brain of the operation. While less common, a faulty BCM can cause this code and is a known issue on Savana vans. It's the last resort after other components are verified as good.
  Trusted brands: ACDelco (GM Genuine)
  OEM price range: $250-$400

Related Codes That Often Appear With This One

• B3060 — This code, 'Unlearned Key Detected,' often appears with B3055. It indicates the system saw a key transponder but didn't recognize its code, which can happen during a failed read attempt or when using an unprogrammed key.
• B3935 — This code relates to 'Transponder Authentication Error' and is part of the same family of security codes as B3055, pointing to a failure in the key validation process.
• B2955 — This code for 'Security System Sensor Data Circuit Malfunction' can sometimes accompany B3055, pointing towards an issue with the circuit that includes the exciter coil in the ignition lock housing.

Technical Service Bulletins (TSBs) & Recalls

• PIC5650M: A Preliminary Information bulletin that addresses intermittent no crank/no start conditions with security light activation, listing B3055 as a primary related DTC. It advises a diagnostic path of checking for aftermarket devices, RF interference, and key issues before replacing modules.
• PIT5030E: Addresses intermittent no-crank caused by the flip-key not being fully extended, which can set a history code for B3055.

Platform-Specific Known Issues

• A Technical Service Bulletin (TSB #PIC5650M) exists for intermittent no crank, no start, or start/stall concerns with the security light on, specifically mentioning DTC B3055. It guides technicians to check for simple causes like RF interference or faulty keys before suspecting major components like the BCM.
• Another bulletin, PIT5030E, notes that on vehicles with flip-keys, not having the key fully extended and locked can cause an intermittent B3055.

Mechanic-Grade Diagnostic Values

• Voltage on Signal Circuit at BCM Connector — expected: < 1.0 V. Failure: Voltage greater than 1.0 V indicates a short to voltage in the wiring harness between the BCM and the ignition lock cylinder housing.
• Resistance of Signal Circuit to Ground — expected: Infinite (Open Line/OL). Failure: Any continuity or low resistance reading indicates a short to ground in the wiring harness.
• Resistance of BCM Ground Circuit — expected: < 10 ohms. Failure: Resistance greater than 10 ohms indicates a poor ground connection, which can cause a variety of BCM-related issues.

Scan Tool Commands That Help

• GM GDS2 / Techline Connect: Immobilizer Learn — This function is required after replacing the BCM or ignition keys. It guides the technician through the process of teaching the vehicle to recognize the new components.
• GM GDS2 / Techline Connect: BCM Setup/Programming — When a new Body Control Module is installed, it must be programmed with the vehicle's specific VIN and configuration data. This function downloads the correct software from GM's servers and configures the module.
• GM GDS2: Data Display > TDM > Transponder Key Status — Used during initial diagnosis to see if the Theft Deterrent Module (function of the BCM) is detecting the key's transponder signal. The status should change from 'Not Present' to 'Present' when a valid key is inserted.

Wiring & Ground Locations

• Body Control Module (BCM) — Inside the passenger cabin, located behind the lower driver's side dashboard, often near the primary fuse block and steering column.. The BCM acts as the Theft Deterrent Module (TDM) for the Passkey III+ system. All signals from the ignition key's exciter coil are processed here. A loose connector or internal failure of the BCM will set this code.
• Ground G218 — On the driver's side, behind the dash panel, attached to a stud on the body.. This is a primary ground point for the Body Control Module. TSB PIT5405C specifically identifies a poor connection at G218 (often due to trapped insulation matting or a loose nut) as a cause for numerous electrical problems, including no-start conditions and various DTCs.
• Ignition Lock Cylinder Housing Connector — At the rear of the ignition lock cylinder, inside the steering column shroud.. This connector carries the signal from the exciter coil (antenna) to the BCM. The two critical wires are the signal and ground. Damage or corrosion at this connector or its pins will interrupt the signal and cause a B3055.

Real Owner Repair Stories

• iATN (International Automotive Technicians Network) forum post (2008 Chevrolet Express 1500 5.3L (Same platform and system)) — No crank/no start, 'Service Theft Deterrent System' message on the cluster, security light on. Scan tool showed B3055.
  ❌ Tried (didn't work) 30-minute relearn procedure
  ✅ What actually fixed it The confirmed fix was replacing the ignition lock cylinder housing, which contains the transponder exciter coil. After replacement, the vehicle started and the code was resolved.

OEM Part Supersession History

• 84922494 → 85133230 (and others prior) — Standard part evolution, potential internal component revisions for reliability.
  Heads up: The BCM is a high-supersession part. While multiple part numbers may have been used over the years (e.g., 22860591, 25934762), it is critical to order the BCM by VIN from the dealer to get the latest correct hardware and software revision for the specific vehicle's options. Installing a used BCM from another vehicle without proper programming will not work.