B16A2 – Turn Signal (LH) Bulb Outage

The Mitsubishi fault code B16A2 – Turn Signal (LH) Bulb Outage is a manufacturer-specific diagnostic trouble code stored by the ETACS (Electronic Time and Alarm Control System) on Mitsubishi vehicles. It indicates that the ETACS has detected an abnormally low current draw on the left-hand turn signal circuit — consistent with one or more bulbs in that circuit having failed, been removed, or replaced with an aftermarket LED that draws insufficient current for the ETACS load detection threshold. B16A2 is the left-hand mirror equivalent of B16A4, and shares identical diagnostic logic, causes, and repair approaches — with the difference being the physical side of the vehicle affected. Because B16A2 falls in the manufacturer-controlled B1xxx range, its definition and diagnostic approach are specific to Mitsubishi vehicles.

What Does B16A2 Mean on a Mitsubishi?

The ETACS supplies and monitors current to both the left and right turn signal circuits independently. For the left-hand circuit this typically includes the front left indicator, the rear left indicator, and on applicable variants a left-side repeater. When the left turn signal is activated, the ETACS measures the total current flowing through the combined left-hand circuit and compares it against a calibrated threshold — typically around 3.0–4.0A with all bulbs functioning correctly on a standard incandescent setup.

B16A2 is stored when this measured current drops below the minimum threshold, indicating that one or more bulbs in the left-hand circuit are absent or have failed. As with B16A4, the ETACS simultaneously increases the flash rate of the remaining left-hand indicators to the driver-alert “hyperflash” rate of approximately 120 flashes per minute — the familiar fast clicking and rapid dashboard arrow that tells the driver to check their indicators.

Symptoms of B16A2

The symptoms of B16A2 are immediate and obvious:

• Left-hand turn signal indicators flashing at double speed — “hyperflash” or “fast flash” — the ETACS’s driver alert for a detected bulb outage
• One or more left-hand indicator bulbs visibly not illuminating when the left turn signal is activated
• The dashboard left turn signal indicator (left arrow) may flash rapidly or be absent if the fault affects the instrument cluster indicator feed
• B16A2 stored in the ETACS module when scanned with MUT-III or a compatible scanner
• Fault may be intermittent initially — the indicator works sometimes but fails unpredictably — pointing to a bulb with a failing filament contact or a corroded socket making intermittent contact
• No effect on vehicle driveability — B16A2 is an electrical body fault only

Common Causes of B16A2

The root causes of B16A2 are almost always at bulb or socket level rather than in the ETACS or wiring:

• Failed incandescent bulb — the most common cause by far; a blown filament in the front left, rear left, or left side repeater indicator causes circuit current to fall below the ETACS threshold
• Aftermarket LED bulb without load resistor — an LED indicator fitted without an inline load resistor draws far less current than the ETACS expects, triggering B16A2 even though the LED is illuminating correctly
• Corroded bulb holder — road salt and moisture ingress cause corrosion on bulb holder contacts, increasing circuit resistance and reducing detectable current without the bulb itself failing
• Damaged or cracked bulb holder — a physically damaged holder that cannot maintain reliable bulb contact causes intermittent or permanent low current detection
• Open circuit in the left indicator feed wiring — a broken wire, corroded connector, or loose terminal between the ETACS and the left indicator unit
• Water ingress into a left-side light cluster — moisture in the front or rear left light housing causes progressive corrosion on holder contacts and connector terminals
• Blown indicator fuse — a blown fuse removing supply to the left indicator circuit entirely
• ETACS current sensing circuit fault — very rare; a false B16A2 from a failed ETACS measurement circuit when all bulbs are actually functioning

Common Misdiagnoses

B16A2 is simple to resolve but these misdiagnoses recur regularly:

• Only the rear bulb checked: The rear left indicator is the most visible and most frequently blamed, but the failed bulb is just as often the front left indicator or the left side repeater. Always check every bulb in the left-hand circuit before replacing anything — a 60-second walk-around with the indicator active identifies the failed position immediately.
• LED bulb replaced with another LED without adding load resistors: When aftermarket LEDs trigger B16A2 the first instinct is to replace them. A new LED without a load resistor will produce exactly the same B16A2 immediately. The fix is load resistors — not a different LED.
• New bulb fitted into a corroded socket: A new bulb fitted into a corroded holder will either fail prematurely or produce an intermittent B16A2 from the first day. Always clean the socket contacts before fitting a replacement bulb.
• Code not cleared after repair: B16A2 will remain stored in the ETACS memory even after a successful bulb replacement. Some owners assume the fault has not been fixed when the code is still present — the code simply needs to be cleared with a diagnostic scanner. If the indicator is now working at normal flash rate, the repair is complete.

Affected Mitsubishi Vehicles

Tools & Equipment Required

Step-by-Step Diagnosis

Start outside the vehicle — the failed bulb position is almost always immediately visible:

• 1
  Activate the Left Turn Signal & Walk AroundWith the ignition on, activate the left turn signal and walk around the vehicle. Identify which specific position is not illuminating — front left indicator, rear left indicator, or left side repeater. This takes 60 seconds and immediately identifies the failed bulb position. Also note whether the hyperflash is active on the remaining functioning bulbs — this confirms the ETACS has detected the outage.
• 2
  Check the Indicator FuseIf all left-hand indicators are absent rather than just one position, check the indicator fuse in the fusebox before removing any light clusters. A blown fuse removes supply to the entire circuit. Replace with an identical fuse rating only — and investigate why the fuse blew before assuming it was a one-off event.
• 3
  Remove & Inspect the Faulty BulbAccess the non-illuminating bulb position. Remove the bulb and inspect it for a broken or blackened filament confirming failure. Also inspect the bulb holder for corrosion, burnt contacts, or physical damage. On high-mileage Mitsubishi models the rear left indicator is particularly susceptible to holder corrosion from water and road salt ingress through the tailgate seal area.
• 4
  Check Supply Voltage at the SocketIf the bulb appears intact but is not illuminating, use a test light or DMM to verify 12V supply is present at the holder when the turn signal is active. Absent voltage confirms an open circuit upstream — trace the feed wire back toward the ETACS to locate the fault. Voltage present but bulb still not working with a new bulb suggests a ground fault on that circuit.
• 5
  Confirm LED / Load Resistor StatusIf aftermarket LED bulbs are fitted to the left indicator positions, verify whether load resistors were installed. Without resistors the ETACS will always detect a current below its outage threshold on the LED circuit regardless of whether the LEDs are illuminating. A clamp ammeter on the left indicator circuit should show approximately 1.75–2.1A per functioning incandescent bulb — an LED without a resistor may show as little as 0.1A per position.

Scanner Readout Explained

Below is a representative MUT-III diagnostic readout for an Outlander PHEV presenting with B16A2 due to a failed front left indicator bulb.

====================================================
  MITSUBISHI MUT-III SE — DIAGNOSTIC REPORT
====================================================
  Vehicle:     2017 Outlander PHEV (GG3W)
  VIN:         JMBXNGA3WHZ0XXXXX
  Date:        2025-03-27  09:51:04
  Technician:  Workshop Bay 1
====================================================

MODULE: ETACS (Electronic Time & Alarm Control System)
----------------------------------------------------
  B16A2  Turn Signal (LH) — Bulb Outage
         Status:       Confirmed / Current
         Freeze Frame:
           Turn Signal Switch:      LEFT ACTIVE
           LH Circuit Current:      2.14A (rear + repeater detected)
           Expected Current:        3.50A (front + rear + repeater)
           Flash Rate:              118 flashes/min (hyperflash)
           Ignition Status:         ON

MODULE: PCU
----------------------------------------------------
  No faults stored.

MODULE: ECM
----------------------------------------------------
  No faults stored.

====================================================
  LIVE DATA (Turn Signal Active — LH)
====================================================
  LH Turn Signal Circuit Current:    2.14A
  LH Front Indicator Status:         NOT DETECTED
  LH Rear Indicator Status:          ACTIVE
  LH Side Repeater Status:           ACTIVE
  Flash Rate Current:                118 flashes/min
  Flash Rate Normal:                 60–90 flashes/min
====================================================

The live data makes the diagnosis unambiguous. The ETACS is measuring 2.14A on the left circuit — consistent with the rear indicator and side repeater functioning but the front left indicator contributing no current. Normal current with all three bulbs active would be approximately 3.5A. The front left indicator bulb was removed and found to have a completely broken filament. Replacing the bulb, cleaning the socket with electrical contact cleaner, and clearing B16A2 resolved the fault — normal flash rate confirmed on retest.

Step-by-Step Repair Guide

Repair Path A: Incandescent Bulb Replacement

• 1
  Access the Bulb HolderAccess the failed bulb position. For the rear left indicator on the Outlander PHEV, open the tailgate and remove the inner trim panel to reach the bulb holder from inside. For the front left indicator, access is typically from the engine bay or by removing the left wheel arch liner. The left side repeater is usually accessed by pushing the repeater unit out of the door mirror housing or wing panel from outside. Consult the workshop manual for your specific model year.
• 2
  Clean the Socket & Fit the Correct BulbRemove any corrosion from the bulb holder contacts using electrical contact cleaner and a small brush. Apply a thin smear of dielectric grease to the bulb base contacts before fitting the replacement. Fit the correct bulb type — PY21W amber is standard for most Mitsubishi indicator positions, but verify against your specific model and market specification. Ensure the replacement bulb seats fully and locks securely.
• 3
  Test Before Refitting Panels & Clear CodeBefore refitting any trim panels, activate the left turn signal and verify the replaced bulb illuminates correctly and the flash rate has returned to normal. Clear B16A2 using MUT-III or equivalent. Reactivate and confirm normal operation. Refit all trim panels and cluster fixings, ensuring any light cluster seals are correctly seated to prevent future water ingress.

Repair Path B: LED Bulb with Load Resistor Installation

• 1
  Fit a 50W 6Ω Load Resistor per LED BulbFor each LED indicator position on the left-hand circuit, wire a 50W 6Ω load resistor in parallel with the LED bulb — positive leg of the resistor to the bulb supply wire, negative leg to the ground wire. This replicates the ~2A draw of an incandescent bulb, restoring the circuit current to above the ETACS threshold. Mount each resistor onto a bare metal bracket or panel — never onto plastic or wiring — to safely dissipate the heat generated under sustained indicator use.
• 2
  Alternative: Use CANbus-Compatible LED IndicatorsAs an alternative to external load resistors, replace the current LEDs with CANbus-compatible LED indicator bulbs. These have a built-in resistor circuit that replicates incandescent current draw internally. They are cleaner to install, require no external wiring, and are widely available for standard PY21W applications. Ensure the CANbus rating matches the ETACS threshold for your specific Mitsubishi variant.
• 3
  Verify & ClearActivate the left turn signal and confirm all LED positions illuminate correctly and flash rate is normal. Clear B16A2 using MUT-III. Confirm B16A2 does not return after clearing. Check all resistor mounting points are secure and clear of combustible materials before closing up.

Repair Path C: Wiring or Socket Repair

• 1
  Replace a Damaged Bulb HolderIf the holder contacts are burnt, severely corroded, or the housing is cracked, replace the bulb holder as a unit. Standalone bulb holders for Mitsubishi indicator positions are available as service parts and fit directly onto the existing light cluster wiring. Clean all mating surfaces before fitting the replacement and apply dielectric grease to the new contacts.
• 2
  Repair Open Circuit WiringIf the supply voltage is absent at the bulb holder, trace the feed wire from the holder back toward the ETACS connector using a DMM, testing continuity at successive points to isolate the break. Repair using correctly rated wire and waterproof solder-splice connectors with adhesive-lined heat shrink. Re-route the repaired section away from any abrasion points and secure with fresh cable ties.

Repair Cost Estimates

Prevention & Maintenance Tips

• Check all indicators at every service: A brief walk-around with all indicators active at each oil change or annual service takes under a minute and catches a failing bulb before it sets B16A2 and creates a roadworthiness issue.
• Replace bulbs in pairs: If one indicator bulb fails after several years of service, the other side is likely at a similar age. Replacing both sides simultaneously prevents B16A4 appearing a few weeks after B16A2 is fixed.
• Apply dielectric grease to all bulb holders at each change: A small amount of dielectric grease on bulb base contacts prevents corrosion and maintains reliable electrical contact throughout the bulb’s service life — particularly important for the rear indicators which are exposed to moisture through tailgate and cluster seals.
• Check light cluster seals after any removal: Whenever a light cluster is removed for any reason — for bulb replacement, bodywork, or cleaning — verify the cluster seal and any foam gaskets are correctly seated before refitting. A poorly seated seal allows water ingress that causes repeated bulb holder corrosion and recurring B16A2.
• Use CANbus LEDs if upgrading: If you upgrade to LED indicators, choose CANbus-compatible bulbs from the outset rather than standard LEDs. The modest extra cost avoids load resistor installation and prevents B16A2 entirely.

Frequently Asked Questions

Can I drive my Mitsubishi with B16A2 stored?

No — a non-functioning or hyperflashing turn signal is illegal for road use in all markets. A failed left indicator also presents a genuine road safety risk to other drivers. The repair is one of the quickest and cheapest on any vehicle — a €3 bulb and five minutes. There is no justification for driving with B16A2 unresolved.

Why is my left indicator clicking so fast and how do I stop it?

The fast clicking and rapid flashing is the ETACS’s deliberate response to detecting reduced current on the left indicator circuit — it is alerting you that a bulb has failed. The only way to stop the hyperflash permanently is to restore the circuit current to normal by replacing the failed bulb or fitting load resistors with LED upgrades. Clearing the code without fixing the underlying cause will result in B16A2 returning immediately on the next indicator activation.

I replaced the bulb but B16A2 is still showing on my scanner — is the repair complete?

If the left indicator is now working at normal flash rate after the bulb replacement, the repair is complete. B16A2 remains stored in the ETACS memory and must be actively cleared with a diagnostic scanner — it does not erase itself. Once cleared, activate the turn signal again to confirm normal operation and verify B16A2 does not return. If it does return immediately after clearing with a new bulb fitted, check the bulb holder contacts and verify the correct bulb type was used.

Both B16A2 and B16A4 are stored at the same time — what does this mean?

Both left and right circuits failing simultaneously is unusual for bulb failures and points most strongly to a blown indicator fuse that has removed the supply from both circuits, or to a common ground fault affecting both indicator circuits. Check the indicator fuse first — if it has blown, replace it, clear both codes, and test both circuits. If both indicators now work normally, investigate why the fuse blew before considering the repair complete.

My left indicator worked this morning but not this afternoon — why is B16A2 intermittent?

Intermittent B16A2 most commonly indicates a bulb with a failing filament that still makes contact under some conditions — typically when cold and stationary — but loses contact as the filament heats up or vibration disrupts a weak internal connection. A corroded bulb holder making intermittent contact as the bulb expands and contracts with temperature cycling produces the same intermittent pattern. Replace the suspect bulb and clean the socket — intermittent faults of this type almost always resolve with a fresh bulb in a clean holder.

Do I need a Mitsubishi dealer to clear B16A2, or can any garage do it?

Any workshop with a scanner that supports Mitsubishi ETACS module access can clear B16A2 — it does not require a Mitsubishi dealer or MUT-III specifically. Tools such as the Autel MaxiSYS, Launch X431 PAD VII, and iCarsoft MIT II all support Mitsubishi ETACS code clearing. Many independent garages will clear a single body code for a nominal fee, and some will do it for free alongside another repair.

Is B16A2 covered under Mitsubishi’s warranty?

A failed indicator bulb on a vehicle within its warranty period would typically be covered as a component defect if the bulb is still within its expected service life. Bulbs that fail very early — within the first year or two — are more likely to be covered than those that fail after several years of normal use. If aftermarket LED bulbs without load resistors caused B16A2, this would not be covered under warranty as it is the result of a non-OEM modification. Present the full diagnostic report to your Mitsubishi dealer when making a warranty enquiry.

Conclusion

Mitsubishi B16A2 – Turn Signal (LH) Bulb Outage is the left-hand equivalent of B16A4 and shares exactly the same diagnostic logic, causes, and repair approach. In almost every case the fix is a €3 incandescent bulb replacement and a quick clean of the bulb socket — one of the most straightforward and least expensive repairs on any Mitsubishi model.

The only additional complexity arises when aftermarket LED indicators have been fitted without load resistors — in which case the LEDs themselves are fine but need to be supplemented with load resistors or replaced with CANbus-compatible units to satisfy the ETACS current threshold. In either scenario the diagnosis is quick, the repair is cheap, and the vehicle is back to full legal roadworthiness within the hour.