B1602

Code

Other B — Body

PATS Received Invalid Format Of Key-Code From Ignition Key Transponder

Brand: Other

Type: B — Body

Views: UK: 35 EN: 54 RU: 45

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Page language: EN

Causes

Damaged or non-programmed key/transponder (wrong type or worn)
Faulty or weak transponder coil/antenna (ignition barrel ring)
Intermittent or damaged wiring/connectors between antenna and PATS/BCM
Corrupted or incompatible transponder data/protocol (after aftermarket key or replacement)
Faulty PATS/immobilizer module or BCM handling transponder data
Scan tool or software mismatch after key programming or module replacement

Symptoms

Engine will not start or cranks but does not run
Security/immobilizer warning lamp illuminated or flashing
No remote/immobilizer recognition tone (if vehicle normally beeps on key read)
Intermittent start problems with a particular key
Key present but system reports unknown/invalid key or key not recognized

What to check

Verify key battery (if remote integrated) and try a known-good/spare key
Scan vehicle for stored immobilizer/PATS codes and freeze frame data
Observe security lamp behavior during key operation and cranking
Inspect antenna ring and connector at ignition barrel for damage, corrosion, or loose pins
Check power and ground to PATS/immobilizer module and antenna circuit
Attempt key read with dealer or aftermarket transponder reader to confirm ID/protocol

Signal parameters

Typical low-frequency carrier ~125 kHz for passive ignition transponders
Modulation type: load-modulated reply from transponder (ASK/FSK variants possible)
Transponder response length: tens to a few hundred bits (varies by protocol)
Expected readable transponder ID in hex or decimal (varies by manufacturer)
Antenna coil continuity/resistance typically a few ohms to a few hundred ohms depending on design
Module communication: immobilizer module communicates ID/validation over vehicle CAN or local serial bus

Diagnostic algorithm

Attempt to start with a verified known-good programmed key or factory spare. If the known-good key works, suspect the original key transponder.
Visually inspect the key for physical damage. If removable transponder pellet present, ensure it is intact.
Use an immobilizer/key reader to read the transponder ID and protocol. Confirm the reader returns a valid ID string and that the format matches manufacturer expectations.
Inspect the antenna ring around the ignition cylinder: check for broken wires, corroded connector pins, secure mounting and proper seating.
With ignition off, measure antenna coil continuity and resistance. Compare to specification or to the spare/known-good vehicle value. Check for short to ground or open circuit.
With a scope (or capable diagnostic tool), observe the carrier on the antenna while key is inserted and turned; verify presence of carrier and the transponder reply waveform when the key is in the read zone.
Check power and ground feeds at the PATS/immobilizer module and verify module communications on CAN/LIN bus if applicable. Look for related codes that indicate module or communication faults.
Inspect wiring harness between antenna, ignition switch, and immobilizer for continuity and shorts; repair as needed.
If transponder ID is read but format/protocol is unsupported, confirm key type is correct for vehicle year/model. Replace with correct OEM transponder or reprogram if possible.
If antenna and key are good but code persists, consider immobilizer module or BCM failure. Reflash or replace module as a last step after confirming all hardware and software matches and after consulting manufacturer procedures.
Clear codes and retest with each repair step. Document which key(s) start the vehicle and whether the security lamp behavior changes.

Likely causes

Key transponder physically damaged or contains wrong transponder type
Antenna ring not reading proper signal (open coil, shorted turns or poor solder/connectors)
Communication failure between antenna and immobilizer module (broken wire, poor ground)
Attempted use of aftermarket/unprogrammed key or wrong replacement key
Immobilizer module firmware/configuration mismatch or hardware fault