OBD-II Diagnostic Trouble Code
B1681 — Power Door Lock Switch Circuit
B1681 is a manufacturer-specific body code defined here as the power door lock switch circuit. The body or door module saw an abnormal switch input, such as a switch stuck closed, a short or an out-of-range resistance. Definitions vary by OEM, and some manufacturers use this number for an unrelated fault such as an anti-theft transceiver code, so confirm the definition for the truck.
Severity 1/5
Truck-relevant
Drive on
Severity
Drive on
Power Door Lock Switch Circuit
Code
B1681
Category
Body
Subsystem
Network
Truck-relevant
Yes
What this means for truckers
Low severity on a Cummins X15, Detroit DD15, PACCAR MX-13. The vehicle is safe to drive to your next planned stop. Address at your next regular service.
Before you replace parts — try this first
B1681 on the Network system is most often stuck or corroded door lock switch — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Power locks do not work from one switch, cycle on their own, or do not respond. Sometimes there is a battery drain because the module stays awake.
Common causes
- CommonStuck or corroded door lock switch ($60–$200)
- CommonBroken wires in the door jamb harness boot ($120–$350)
- OccasionalWater intrusion in the door panel or switch connector ($80–$250)
- RareFaulty body or door module ($300–$900)
How to fix
Watch the switch input on a scan tool while pressing the switch
When to use: First step, to see whether the input changes correctly
Inspect and repair the wiring through the door hinge boot
When to use: When the input drops out as the door opens and closes
Replace the switch
When to use: When the switch input reads stuck or does not change
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 B1681?
Yes — B1681 is severity 1. The vehicle is safe to drive to your next planned stop. Address at your next regular service. The check engine light will stay on until the underlying issue is fixed and the ECM monitors clear.
How much does it cost to fix B1681 on a commercial truck?
Total repair cost ranges $60–$900 depending on the root cause. The cheapest fix is usually the first one listed below — Stuck or corroded door lock switch — 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 B1681 fail a DOT inspection?
B1681 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 B1681 and related codes?
B1681 is closely related to: B1601 (PATS Received Invalid Format Of Key Code). These codes share the same subsystem (network) 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 B1681 is set without the companions, the issue is more isolated.
How do I prevent B1681 from coming back after a repair?
For B1681 (Power Door Lock Switch Circuit), prevention centers on the network system. Pay attention to ground connections at every PM — bad grounds are 70% of communication codes. Inspect harness routing for chafe points. Don't disconnect modules with the key on.