B1606 — Lamp Anti-Theft Indicator Circuit Short To Ground

B1606 — Lamp Anti-Theft Indicator Circuit Short To Ground. A fault in the body electrical system. The car is usually drivable while you plan the repair. Typical causes: body control module (BCM) fault, damaged wiring in door jambs or wet areas, blown fuse or failed relay.

body electrical

Is it safe to drive?

Short-term driving is OK Usually safe to drive — body codes rarely affect drivability. Exceptions: exterior lighting and wipers in bad weather, and central locking faults that can leave the car unsecured.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm B1606 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 body electrical system for damage, corrosion, chafing or poor contact.
Subsystem check Operate the affected function while watching its switch and motor PIDs in live data.
Subsystem check Inspect connectors and wiring at flex points (door jambs, tailgate hinges) — wires break there first.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm B1606 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for B1606 (parts and labor, USD, independent shop rates): Repair wiring or connectors: $80–$250; Replace the switch or actuator: $120–$450; BCM repair or replacement: $300–$900. Overall, fixing B1606 usually costs between $80 and $900. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

How much does it cost to fix B1606?

Repair wiring or connectors — $80–$250; Replace the switch or actuator — $120–$450; BCM repair or replacement — $300–$900. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

What are the symptoms of B1606?

Drivers most often notice: the affected function (locks, windows, lighting, wipers) works intermittently or not at all, warning light on the dashboard, no impact on engine operation in most cases.

Will B1606 clear itself?

Sometimes B1606 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What is the most common cause of B1606?

The most common causes are: body control module (BCM) fault, damaged wiring in door jambs or wet areas, blown fuse or failed relay.

How do I diagnose B1606 myself?

Start with a scan: confirm B1606, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the body electrical system, and verify the suspect component against live data before buying parts.

When your scan tool pulls code B1606, it is reporting that the vehicle's body control module has detected a short circuit to ground somewhere in the anti-theft indicator lamp circuit. In plain terms, the circuit that should carry power to a telltale lamp is leaking current to the vehicle's metal chassis instead. This places B1606 squarely in the body electrical category of OBD2 codes — it has no direct connection to engine management, fuel delivery, or emissions controls.

The anti-theft indicator lamp lives on your dashboard and serves a simple purpose: it tells you when the factory security system is armed or has triggered an alarm. Under normal operation, the body control module energizes this lamp through a dedicated circuit. When a wire's insulation wears through, moisture infiltrates a connector, or corrosion builds up at a plug, current takes a shortcut directly to ground. The module recognizes this abnormal condition, logs B1606, and illuminates the check-engine light or a dedicated body fault indicator. Most manufacturers require the fault to appear on two consecutive drive cycles before storing a permanent code, which is why the light sometimes flickers on and off before staying on.

Understanding the freeze frame data that accompanies B1606 is one of the most practical diagnostic shortcuts available. When the module sets the code, it records a snapshot — engine rpm, calculated load, coolant temperature, and vehicle speed at the exact moment the short was detected. This snapshot tells you whether the fault occurred during a cold start, at highway speed, or when the doors were being locked. Using that information to recreate the driving conditions during your road test makes it far easier to confirm whether the code has been truly cleared or whether the underlying short is still present.

Common Symptoms of B1606

The anti-theft indicator lamp fails to illuminate when the security system is armed, or it stays illuminated continuously instead of cycling normally.
The related body function — typically the factory alarm, door locks, or an associated dome-light circuit — operates erratically or not at all.
The dashboard displays a general warning light or a dedicated body-control warning message.
Other body electrical features such as power windows, interior lighting, or wipers show intermittent behavior because they share the same ground or power bus.
The check-engine light may activate, though the engine itself runs and drives without any performance change in the vast majority of cases.
In rare instances where the short disrupts BCM communication, multiple unrelated accessories may exhibit strange behavior simultaneously.

Possible Causes of B1606

The most frequent culprits behind B1606 involve the wiring and connectors that make up the anti-theft lamp circuit:

Corrosion or moisture intrusion at the connector that joins the anti-theft indicator bulb or its housing to the body harness.
A loose or poorly seated electrical plug at the instrument cluster, body control module, or anti-theft module.
Chafed or broken wire insulation in high-flex areas such as the driver's door jamb, where repeated opening and closing stresses the harness.
A faulty anti-theft indicator bulb or its socket, which can create resistance that the module interprets as a short.
A defective switch, actuator motor, or relay that shares circuitry with the anti-theft indicator circuit, causing cross-circuit interference.
A body control module that has failed internally and no longer properly regulates the indicator circuit voltage.
A blown fuse or an intermittently failing relay that disrupts proper circuit operation.

How to Diagnose B1606

Connect an OBD2 scanner and verify that B1606 is the stored code. Record the freeze frame data before clearing anything — that snapshot contains the conditions under which the fault first appeared.
Research whether your specific make and model has a published TSB for B0xxx body codes. Many manufacturers have issued software updates or harness modifications that resolve recurring indicator circuit faults without any physical repair.
Perform a thorough visual inspection of the entire anti-theft indicator circuit. Start at the instrument cluster and work outward toward the BCM. Look for cracked insulation, rubbed-through wires, white or green corrosion deposits, and any connector that shows signs of moisture entry.
Use a digital multimeter to check for continuity between the indicator circuit and chassis ground. A reading below approximately 5 ohms confirms the short-to-ground that sets B1606.
Disconnect the BCM one circuit at a time while monitoring the multimeter to isolate which branch of the harness contains the short.
After identifying and repairing the faulty section, clear the code, complete a full drive cycle that reproduces the freeze frame conditions, and re-scan to verify that B1606 does not return.

Repair Options for B1606

Repair costs for B1606 depend entirely on which component in the anti-theft indicator circuit has failed. The following ranges reflect typical parts and labor at an independent repair shop in the United States.

Wiring repair or connector replacement: $80–$250. In most cases, fixing corroded terminals, soldering a broken wire, or replacing a single damaged connector resolves the short without touching any major components.
Switch, actuator, or indicator bulb/socket replacement: $120–$450. If testing reveals that a specific component is drawing the circuit to ground, replacing that part eliminates the code.
BCM repair or replacement: $300–$900. A module that has suffered internal damage from the short must be removed, bench-tested, and either repaired through a specialist or replaced with a new or refurbished unit. Programming or relearning may be required.

A practical approach saves money: address the wiring and connectors first, test the specific component second, and only consider BCM work if every other possibility has been ruled out.

Can You Drive with B1606?

B1606 carries a short severity rating, which means the vehicle generally remains safe and driveable. The anti-theft indicator circuit does not control engine operation, transmission shifting, or braking systems. However, the underlying short can drain the battery over time if it remains active, and a malfunctioning alarm or lighting circuit can create safety concerns — particularly if exterior lights or wipers are affected during nighttime or inclement weather. If the central locking system shares the faulty circuit, there is also a risk of being locked out or leaving the car unsecured. Addressing the code promptly is advisable even though immediate drivability is not compromised.