B1601 — PATS Received Incorrect Key-Code From Ignition Key Transponder

OBD2 code B1601 flags a problem with the ignition system (PATS received incorrect key-code from ignition key transponder). Short, gentle driving to a shop is usually possible. Common culprits: damaged coil wiring or connector, failed ignition coil or coil pack, moisture or oil in the spark plug wells.

body electrical

Is it safe to drive?

Drive with caution Drive with caution and avoid load. Ignition faults cause misfires that quickly overheat and destroy the catalytic converter; if the Check Engine Light flashes, stop and fix it first.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm B1601 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many B0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the ignition system for damage, corrosion, chafing or poor contact.
Subsystem check Swap the coil to another cylinder and see if the fault code follows it.
Subsystem check Inspect spark plugs for wear, oil or carbon tracks and check plug gaps.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm B1601 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for B1601 (parts and labor, USD, independent shop rates): Repair coil wiring or connector: $80–$250; Replace spark plugs: $90–$250; Replace an ignition coil: $150–$380. Overall, fixing B1601 usually costs between $80 and $380. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What are the symptoms of B1601?

Drivers most often notice: hard starting, especially in damp weather, misfires under load or at idle, Check Engine Light on, loss of power and jerking.

Is it safe to drive with B1601?

Drive with caution and avoid load. Ignition faults cause misfires that quickly overheat and destroy the catalytic converter; if the Check Engine Light flashes, stop and fix it first.

How much does it cost to fix B1601?

Repair coil wiring or connector — $80–$250; Replace spark plugs — $90–$250; Replace an ignition coil — $150–$380. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

What does OBD2 code B1601 mean?

How do I diagnose B1601 myself?

Start with a scan: confirm B1601, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the ignition system, and verify the suspect component against live data before buying parts.

When your vehicle's computer detects a problem with the ignition signal pattern, it logs OBD2 code B1601. The full technical description reads "PATS Received Incorrect Key-Code From Ignition Key Transponder," which points directly to the Passive Anti-Theft System that governs whether your engine will start. This code lives in the body electronics category rather than the powertrain category, which tells you the problem centers on the security system and its communication with the ignition components rather than a pure mechanical engine failure.

The PATS system relies on a transponder embedded in your ignition key. When you turn the key, the module sends a low-frequency signal to the chip, which responds with a unique code. If that code doesn't match what the system expects, the ECU interprets this as an authentication failure. Code B1601 specifically means the module received a signal from the transponder, but the data was corrupted, incomplete, or just wrong. The ECU typically runs this check across multiple drive cycles before confirming the fault, and it captures a freeze frame snapshot at the moment of detection—recording RPM, engine load, coolant temperature, and vehicle speed. That snapshot becomes your roadmap for diagnosis.

Symptoms of B1601

Engine cranks but refuses to start, particularly when the weather is damp or humid
Intermittent misfiring that worsens under acceleration or at idle
Check Engine Light or security indicator illuminated on the dashboard
Noticeable loss of engine power and hesitation during acceleration
Fuel economy dropping noticeably compared to normal driving patterns
Rough idle or stalling shortly after startup
In some vehicles, the starter may not engage at all due to the anti-theft system disabling the starter relay

Common Causes of B1601

Faulty ignition coil or failing coil pack—the most frequent culprit behind this code
Worn or improperly gapped spark plugs that produce weak spark output
Damaged, corroded, or loose wiring harness feeding the ignition circuit
Moisture intrusion or oil contamination inside spark plug wells affecting spark quality
Defective ignition control module or ECM circuitry related to the PATS interface
Failed key transponder chip or damaged key fob circuitry
Poor electrical connection at the ignition coil connector from vibration or contamination

How to Diagnose B1601

Link up your OBD2 scanner and pull all stored codes. Confirm B1601 is present, then record the freeze frame data—this shows the exact engine conditions when the fault triggered and guides your next steps.
Look for any accompanying trouble codes in the B0xxx range. Secondary codes often expose the real underlying problem. Cross-reference any findings against manufacturer TSBs for your specific make and model; many vehicles have documented software patches or hardware updates addressing these issues.
Perform a thorough visual inspection of the ignition wiring harness, focusing on the coil feed circuits. Check for frayed insulation, corrosion at connectors, broken wire strands, and any signs of moisture or oil intrusion near plug wells.
Test the ignition coil output with a multimeter or oscilloscope. If equipment allows, swap the suspect coil with a known-good cylinder and monitor whether the fault code migrates to the other cylinder.
Remove and inspect spark plugs for wear, carbon buildup, oil fouling, or incorrect gap settings. Replace any plugs showing obvious degradation or exceeding manufacturer gap specifications.
Clear the code and complete a drive cycle that replicates the conditions captured in the freeze frame—similar RPM, load, and temperature conditions. If B1601 reappears, the root cause has been identified.

Repair Options and Costs

Addressing B1601 means fixing whatever component in the ignition chain is generating the bad signal:

Ignition coil replacement runs $150–$380 for parts and labor at an independent shop
Spark plug set with installation costs $90–$250
Wiring repair or connector replacement for the coil circuit runs $80–$250

Most shops bill labor separately from parts, so expect a diagnostic fee of $75–$150 on top of these figures if you bring the vehicle in for professional assessment. Independent shops consistently charge less than dealerships for the same work.

Total Cost to Fix B1601

The total repair bill for B1601 typically falls between $80 and $380 depending on which component actually failed. The good news is that the most expensive scenario—an ignition coil replacement—ranks among the easier fixes to confirm through swapping or testing. Always verify the exact fault before purchasing parts; replacing the wrong component wastes money and time.

Can You Drive with B1601?

Use caution if the Check Engine Light is solid, and stop driving immediately if the light flashes. Ignition misfires generated by this fault send unburned fuel into the exhaust stream, and that raw fuel overheats the catalytic converter—potentially causing thousands in damage. Drive conservatively, avoid heavy loads and high RPMs, and schedule diagnosis promptly. If your vehicle is immobilized by the anti-theft system, you won't have a choice but to address it before going anywhere.