Faulty ignition coil with built-in igniter for cylinder 8; Open or short circuit in the igniter circuit wiring (power, ground, or signal); Corroded or loose electrical connector at the ignition coil or ECM; Failed spark plug or excessive spark plug gap causing coil stress; ECM internal fault affecting the igniter control signal; Aftermarket or incorrect ignition coil installed previously

DTC codes / Toyota codes / P1340

P1340 · ToyotaIgniter Circuit Malfunction No 8

Q: What does code P1340 mean?

Igniter Circuit Malfunction No 8. P1340 on Toyota vehicles indicates that the engine control module (ECM) has detected a malfunction in the igniter circuit for cylinder number 8, which is part of the ignition coil with built-in igniter assembly. The ECM monitors the feedback signal from the igniter and sets this code when the expected confirmation pulse is missing or abnormal during engine operation.

P1340 on Toyota vehicles indicates that the engine control module (ECM) has detected a malfunction in the igniter circuit for cylinder number 8, which is part of the ignition coil with built-in igniter assembly. The ECM monitors the feedback signal from the igniter and sets this code when the expected confirmation pulse is missing or abnormal during engine operation.

SystemPowertrain

Code typeToyota specific

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Check Engine Light (CEL) illuminated on the dashboard
Engine misfire or rough running, especially under load
Noticeable loss of power or hesitation during acceleration
Increased fuel consumption due to incomplete combustion
In some cases, no drivability symptoms besides the warning light

Common causes, most likely first

Faulty ignition coil with built-in igniter for cylinder 8
Open or short circuit in the igniter circuit wiring (power, ground, or signal)
Corroded or loose electrical connector at the ignition coil or ECM
Failed spark plug or excessive spark plug gap causing coil stress
ECM internal fault affecting the igniter control signal
Aftermarket or incorrect ignition coil installed previously

How to diagnose and fix it

Perform a visual inspection of the ignition coil, connector, and wiring for cylinder 8
Swap the ignition coil from cylinder 8 with a known-good coil from another cylinder and see if the code follows
Check spark plug condition and gap; replace if worn or fouled
Use a multimeter to test the igniter circuit for continuity, shorts, and proper voltage
Inspect the ECM connector and pins for corrosion or damage
If the coil is faulty, replace it with an OEM-quality unit and clear the code
Verify repair by test-driving and confirming the code does not return

Igniter Circuit Checks Before Coil Replacement

A misfire code for cylinder 8 may not always set P1340; this code specifically indicates an electrical fault in the igniter feedback circuit, not just a misfire.
The igniter is integrated into the ignition coil on many Toyota engines, so a coil failure can trigger this code even if the coil still produces spark.
Wiring harness damage near the coil pack is common due to heat and vibration, often causing intermittent P1340 without a permanent no-start.
Swapping coils is a quick diagnostic step, but be aware that some Toyota models use different part numbers for front and rear banks, so swap only within the same bank.
A weak battery or charging system issue can cause low voltage to the igniter, leading to a false P1340; always check battery voltage and connections first.

Can I keep driving with P1340?

Driving with P1340 is generally safe for short distances, but avoid heavy acceleration or towing because a misfire can overheat the catalytic converter. If the engine runs very rough or flashes the check engine light, stop and repair immediately.

Tools that help

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Guidance is general and written for Toyota vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.