OBD-II Diagnostic Trouble Code
B1601 — PATS Received Invalid Format Of Key Code
B1601 is a Ford Passive Anti-Theft System (PATS) code meaning the transceiver read a key code that was not in a valid format. The key's transponder signal was corrupted, incomplete or unreadable. The PATS module will not authorize the PCM to start or keep the engine running.
Severity 3/5
Truck-relevant
Service this week
Severity
Service this week
PATS Received Invalid Format Of Key Code
Code
B1601
Category
Body
Subsystem
Safety
Truck-relevant
Yes
What this means for truckers
Service within a few days on a Cummins X15, Detroit DD15, PACCAR MX-13. Performance is likely degraded. Continuing to drive without service risks additional component damage.
Before you replace parts — try this first
B1601 is an airbag (SRS) circuit code, most often damaged key, a non-transponder key, or an aftermarket key with a bad chip. Airbag circuits are not treated like ordinary sensors:
- Treat the airbag as possibly disabled. With an SRS code set, the airbag may not deploy in a crash. Get it diagnosed soon.
- Disconnect the battery and wait before touching anything. Follow the service manual wait time (often 1–10 minutes) so the SRS module reserve power drains.
- Never probe a squib circuit with a test light or ohmmeter. Use the manufacturer's SRS simulator/load tool and a scan tool that reads SRS codes.
- Check the cheap items first. Seat and clockspring connectors under the seat or behind the wheel are common causes after seat or steering work.
- Replace parts only after diagnosis. Some modules must be replaced, not reset, after a deployment.
Symptoms
Crank-no-start or start-and-stall, with the theft or security light flashing or staying on. It may happen with only one key, or intermittently.
Common causes
- CommonDamaged key, a non-transponder key, or an aftermarket key with a bad chip ($50–$250)
- OccasionalFaulty PATS transceiver ring around the ignition lock ($120–$350)
- OccasionalInterference from other transponders, fobs or metal objects on the key ring ($0–$50)
- RareWiring or connector fault at the transceiver ($100–$300)
How to fix
Try a known-good programmed spare key with nothing else on the ring
When to use: First check to separate a key problem from a vehicle problem
Replace and program the faulty key
When to use: When the spare key works
Check transceiver power, ground and data wiring, and replace the transceiver
When to use: When all keys fail
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
Frequently Asked Questions
Can I drive with code B1601?
B1601 is severity 3 — plan service within a few days. Performance is likely degraded already (you may feel reduced power, harsher shifts, or slightly worse fuel economy). Continuing to drive risks additional damage to adjacent components.
How much does it cost to fix B1601 on a commercial truck?
Total repair cost ranges varies depending on the root cause. The cheapest fix is usually the first one listed below — Damaged key, a non-transponder key, or an aftermarket key with a bad chip — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will B1601 fail a DOT inspection?
B1601 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between B1601 and related codes?
B1601 is closely related to: B1681 (Power Door Lock Switch Circuit). These codes share the same subsystem (safety) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only B1601 is set without the companions, the issue is more isolated.
How do I prevent B1601 from coming back after a repair?
For B1601 (PATS Received Invalid Format Of Key Code), prevention centers on the safety system. Don't disconnect the battery without the key off and a 5-minute wait — capacitors can hold airbag-deployment charge. Don't jumper or test airbag circuits with a multimeter (use OEM scan tool). Replace seat belts and connectors that have been involved in a deployment.