B1601

Code

Other B — Body

PATS Received Incorrect Key-Code From Ignition Key Transponder

Brand: Other

Type: B — Body

Views: UK: 27 EN: 53 RU: 44

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Unprogrammed or erased key transponder ID
Damaged or defective ignition key transponder (chip)
Faulty or misaligned antenna/coiled reader around the ignition lock
Intermittent or open wiring/connectors between antenna and PATS module
Corrupted or erased learned keys in the immobilizer module
ECU or immobilizer module software/hardware fault

Symptoms

Engine cranks but will not start (fuel/ignition disabled)
No-crank in some systems (starter inhibited until key recognized)
Security/immobilizer or key-warning lamp illuminated on dash
Intermittent starting that depends on key angle or position
Key not always recognized after being inserted or turned
VIN/immobilizer related faults stored in vehicle modules

What to check

Confirm which key is being used — test with all known-good programmed keys
Scan all modules for stored immobilizer/PATS and related codes
Visually inspect key for damage, corrosion, or moisture intrusion
Inspect antenna/coil ring around the ignition lock for damage or loose mounting
Check wiring and connectors between antenna and PATS/BCM for continuity and corrosion
Observe dash immobilizer lamp behavior during key insertion/turn — note any blink codes

Signal parameters

Transponder systems typically use a low-frequency (LF) interrogation field — commonly ~125 kHz for passive transponders
Smart/proximity systems may use HF (13.56 MHz) or UHF for remote communications — refer to vehicle spec
Expected: coil/antenna provides an LF field when ignition is in READ position; transponder replies with encoded ID
Scan tool should display an ID string (hex or decimal) when a programmed key is present; mismatched or missing ID indicates problem
Antenna coil voltage signal: low-voltage AC pulses when key inserted/turned (measure with oscilloscope across coil leads)
No valid reply or wrong ID from the key results in immobilizer module rejecting engine enable

Diagnostic algorithm

Record the exact code (B1601) and any additional stored codes. Note dash/instrument cluster lamp behavior.
Verify simple causes: try a known-good programmed key and confirm whether the fault follows the key.
Inspect physical key for damage; if key is a smart-fob check/replace its battery and retest.
Scan immobilizer/PATS module with factory or capable aftermarket tool to read the transponder ID and compare to stored keys.
With the ignition key inserted/turned to read position, observe antenna coil activity with a scope or oscilloscope across coil leads; look for LF field pulses and a transponder reply.
Check continuity and resistance of wiring between ignition coil/antenna and the PATS module; inspect connectors for corrosion or bent pins.
If antenna/coil is suspected faulty, test or replace the antenna ring assembly and retest recognition of key.
If the key ID does not appear in the immobilizer memory, attempt PATS re-learn/program procedure per manufacturer instructions using dealer or OEM-capable tool.
If programming fails or module reports memory faults, consult manufacturer service information — immobilizer module replacement or reflash may be required.
After repairs or reprogramming, clear codes and verify consistent key recognition and normal engine enable behavior.
Note: Immobilizer/key programming is often protected — follow manufacturer security procedures and consider dealer support.

Likely causes

Using an unprogrammed spare key or aftermarket key
Damaged transponder in the key (dropped, water-damaged)
Loose or damaged antenna ring/coils at the ignition cylinder
Communication fault between antenna and immobilizer module (broken wire, bad connector)

Fault status

⚠️ Status

PATS detected a transponder code from the ignition key that does not match any programmed key IDs. Engine enable was denied until a recognized key is used or the system is repaired/reprogrammed.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours