How to Fix Diagnostic Code P1630

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šŸšØ Diagnostic Profile

Vehicle Make: Chevrolet (CHEVY)

Short Description: Theft Deterrent System (PASS-Key / immobilizer family) reporting Learn Mode Active. The vehicle’s immobilizer is in a key-programming state and is not authorizing normal engine start until the learn sequence is completed or cancelled.

šŸšØ Repair Difficulty Tier

Tier: [Intermediate]

Basic inspection and learn-mode cancellation can be performed with a scan tool. Key programming, module replacement, or immobilizer resynchronization requires a professional-grade scan tool with security access and may require dealer or locksmith-level software.

šŸ› ļø Resolution Steps

Step 1: Preliminary Inspection

  • Confirm the exact model year, engine code, and body/module configuration using the VIN, as PASS-Key/PK3/VATS theft deterrent architecture and the Body Control Module (BCM) or Powertrain Control Module (PCM) tasked with immobilizer authority varies significantly across Chevrolet platforms and model years.
  • Verify battery voltage at the main battery terminals using a digital multimeter: confirm a stable resting voltage of approximately 12.4Vā€“12.6V with the key off, and that voltage does not sag below 10.5V during cranking. Low or unstable voltage is a common root cause of false Learn Mode activation or incomplete key authentication cycles.
  • Inspect the ignition switch and key cylinder for mechanical wear, binding, or evidence of forced entry/tampering that could trigger theft deterrent faults.
  • Inspect the transponder key and spare key(s) for physical damage, worn chip contacts, or a cracked transponder housing; confirm the number of keys currently recorded in the vehicle’s immobilizer memory against the number of physical keys presented.
  • Check the security/theft indicator lamp on the instrument cluster for behavior patterns during key cycles (steady illumination, flashing, or extinguished) as this indicates whether the system is in a fault state, learn state, or normal armed state.
  • Inspect the immobilizer/theft deterrent module and related wiring harness connectors for corrosion, pin damage, or chafing. On most Chevrolet platforms this circuit routes through the ignition lock cylinder/key-in-ignition sensor, the BCM, and the data bus connection to the PCM ā€” inspect connectors at the steering column, BCM mounting location (typically under the dash near the steering column or kick panel), and ground straps near the column.
  • Check for aftermarket remote starters, alarms, or bypass modules spliced into the ignition, data bus (GMLAN/CAN), or theft deterrent circuits, as improperly installed aftermarket accessories are a leading cause of persistent Learn Mode faults and communication errors.

Step 2: Diagnostic Verification

  • Connect a compatible scan tool (OEM GM Tech 2/MDI with GDS2, or an aftermarket tool with bi-directional security/immobilizer access) and read all stored DTCs in the Body Control Module and Theft Deterrent/Immobilizer module.
  • Confirm whether the module reports Learn Mode Active, and record the current key-learn count and the elapsed/remaining learn timer if displayed (many GM PASS-Key systems require a 10-minute uninterrupted learn cycle with the key in RUN).
  • Verify network communication between the Theft Deterrent module, BCM, and PCM over the vehicle’s serial data bus (GMLAN/CAN); confirm no U-codes (U0100, U0101, U1000-series) indicating loss of communication are present, as these point to wiring or module power/ground faults rather than a true key fault.
  • Check for active or history DTCs specifically related to key authentication failure (such as password mismatch, invalid resistor pellet ID on older PASS-Key systems, or transponder signal not recognized on PK3 systems) versus communication loss codes.
  • Confirm the module’s software calibration/software version via the scan tool and cross-reference against GM TIS2Web or equivalent service information to determine if a published Technical Service Bulletin or software recalibration applies to this VIN.

Step 3: Resolution & Reset Process

  • Cancel Learn Mode using the scan tool’s dedicated Theft Deterrent/Security function, following the exact manufacturer-published procedure for the identified model year (procedures differ between resistor-pellet PASS-Key, PASS-Key III, PK3+, and passlock-style systems).
  • If key learning is required, program each valid key in the manufacturer-specified sequence (typically requiring all keys to be programmed in a single uninterrupted session) and confirm the total learned key count matches the customer’s physical key count before exiting the procedure.
  • Clear stored DTCs only after the root cause (wiring fault, low voltage event, failed key, or module fault) has been confirmed and corrected ā€” do not clear codes as a blind first step.
  • Cycle the ignition through multiple OFF-to-RUN cycles and verify that the security indicator extinguishes normally and the engine starts and continues running with each programmed key.
  • If the module cannot be cancelled from Learn Mode or will not accept reprogramming despite confirmed good wiring and voltage, replace and reprogram the Theft Deterrent/BCM module per the manufacturer’s service and programming procedure, including any required module-to-vehicle security relearn.
  • Re-verify all key functions, remote keyless entry functions, and confirm absence of stored or pending security-related DTCs across all modules before returning the vehicle to the customer.

šŸ“¦ Parts, Labor, and Budget Estimates

Required Components/Software:

  • OEM-level scan tool with bi-directional immobilizer/security access (GM Tech 2, MDI/GDS2, or equivalent aftermarket tool with GM security module support)
  • Programmable transponder key(s): quantity dependent on customer key count, typically 1ā€“3 keys
  • Immobilizer/Theft Deterrent module or BCM (only if confirmed faulty through wiring/communication testing) ā€” exact GM part number must be sourced via VIN-specific parts lookup, as it varies by model, year, and trim
  • GM TIS2Web or Subscription-based OEM programming software license (required for module-level reprogramming and key relearns on most 2006+ platforms)

Average Component Price:

  • Programmable transponder key (including cutting/blank): approximately $65ā€“$180 per key depending on key type (standard chip, remote head key, or proximity fob)
  • Immobilizer/Theft Deterrent module or BCM: approximately $250ā€“$650 for the part alone, varying by model and whether it is a standalone theft module or integrated BCM
  • Scan tool/software access (shop overhead, often billed as a diagnostic or programming fee rather than itemized to the customer): approximately $50ā€“$150 per programming session if outsourced to a dealer or mobile locksmith

Estimated Labor Hours:

  • Diagnosis and Learn Mode cancellation: approximately 0.5ā€“1.5 hours shop book time
  • Key programming (per key, after initial diagnostic setup): approximately 0.3ā€“0.5 hours per additional key
  • Module replacement and full reprogramming/relearn (if required): approximately 1.5ā€“3.0 hours shop book time, depending on module accessibility and whether a full security relearn with the PCM is required