P1355
FordIgnition Coil D Primary Circuit Malfunction
The engine computer has detected an electrical fault in the primary control circuit for ignition coil D. The primary circuit controls the coil’s operation; this code does not by itself prove the coil has failed. Depending on the vehicle’s ignition setup and the fault, the engine may misfire, run poorly, or show no noticeable symptoms.
⚠️ Before You Begin (Safety First)
If the check-engine light is flashing, the engine is shaking badly, or power loss makes the vehicle unsafe, stop driving when safe and have it diagnosed. A continuing misfire can damage the catalytic converter.
Common Symptoms
- The check-engine light may be on; it may flash if an active misfire is occurring.
- The engine may idle roughly or hesitate if the circuit fault interrupts spark.
- Misfiring can cause reduced power or poor acceleration.
- Fuel economy may worsen if combustion is incomplete.
- There may be no noticeable symptoms if the fault is intermittent or has not caused a clear misfire.
Common Causes
- A fault within ignition coil D, including an internal primary-circuit failure.
- A loose, damaged, corroded, or poorly connected coil connector.
- Open or shorted wiring in the coil D primary circuit.
- A problem with the circuit’s power supply or ground, where applicable to the vehicle design.
- A fault in the engine-computer coil driver, considered after the coil and circuit have been tested.
Diagnostic Steps
- With the engine off and cool, check the ignition coil D connector for looseness, visible damage, corrosion, or signs of heat; a poor connection can interrupt the primary circuit.
- Look over accessible wiring to the coil for chafing, cuts, pinching, or damage. Do not pull on wires or probe connector terminals without the correct service information.
- Note whether the engine runs roughly and whether the check-engine light is flashing. Stop driving if the misfire is severe or the vehicle is unsafe.
- Have the code and any related codes or misfire data checked. Use model-, year-, and engine-specific service information before attempting electrical tests or replacing parts.
When to Call a Professional
Confirm the code and check for related codes and misfire data. Use the correct wiring diagram and vehicle-specific diagnostic procedure to inspect coil D’s connector and wiring, then test the circuit and coil as specified. Check the engine-computer driver only after the coil and its power and wiring have been evaluated; do not replace parts based on the code alone.
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Commonly Asked Questions
Does P1355 prove that ignition coil D is bad?
No. It identifies a detected malfunction in coil D’s primary circuit. The coil, its connector or wiring, the circuit’s supply or ground, or the engine-computer driver may be involved.
Does this code identify a particular cylinder?
The definition identifies ignition coil D, not a cylinder number. The coil-to-cylinder relationship depends on the vehicle’s ignition system and must be checked for the specific model, year, and engine.
Can I keep driving with P1355?
If the engine runs normally and the warning light is steady, arrange diagnosis soon and watch for changes. Stop driving when safe if the light flashes, the engine misfires severely, or the vehicle loses enough power to be unsafe.
Should I replace the coil first?
Not without testing. Check the connector and wiring and follow the vehicle-specific procedure to distinguish a coil fault from a circuit or driver problem.
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