What to Do When You Find a P0351 Ignition Coil Primary/Secondary Circuit Malfunction

P0351 is an OBD-II diagnostic trouble code indicating a malfunction in the primary or secondary circuit of the ignition coil “A”. This code indicates that there is a problem with the voltage coming from the powertrain control module (PCM) to the ignition coil. The PCM supplies a ground and a voltage signal to each of the ignition coils, which then produces spark at the spark plugs. If either of these signals is not being received, then P0351 will be triggered. The most common causes for this code are faulty wiring, faulty PCM, or bad ignition coil.

Poor Maintenance

Poor maintenance is one of the most common causes of ignition coil A primary/secondary circuit malfunction. Ignition coils are designed to last for a long time, but if they are not regularly serviced and maintained, they can wear down and eventually fail. Poor maintenance can include not changing the spark plugs, not replacing worn parts, or failing to properly clean and lubricate the ignition system. Ignition coils should be checked and serviced at least once a year for optimal performance.

Faulty Wiring

Faulty wiring is another potential cause of an ignition coil A primary/secondary circuit malfunction. Faulty wiring can prevent the current from flowing correctly between the different components of the ignition system, leading to misfires or other issues with engine performance. Faulty wiring can be caused by loose connections, frayed wires, or corrosion on the electrical contacts. To prevent this from happening, it’s important to inspect all wiring regularly and replace any damaged components as soon as possible.

Outdated Parts

Outdated parts are also a potential cause of an ignition coil A primary/secondary circuit malfunction. Over time, parts may become worn out or obsolete due to age or lack of use. This can lead to problems with engine performance as these outdated parts may not be able to handle the load of a modern engine. It is important to keep all parts up-to-date by regularly checking for new versions and replacing any outdated components as soon as possible.

Signs of Ignition Coil A Primary/Secondary Circuit Malfunction

One of the most common signs of an ignition coil A primary/secondary circuit malfunction is engine misfiring. If your vehicle is experiencing misfires or jerking motions while driving, it could be due to a failing ignition coil. Other signs include stalling after starting up, decreased fuel economy, poor acceleration performance, and increased exhaust emissions levels. If you suspect that your vehicle may have an issue with its ignition coil A primary/secondary circuit malfunction, it’s important to have it inspected by a professional mechanic right away in order to prevent further damage from occurring.


An automobile is a wheeled motor vehicle used for transportation. Most definitions of cars say they run primarily on roads, seat one to eight people, have four tires, and mainly transport people rather than goods. Cars came into global use during the 20th century, and developed economies depend on them. The year 1886 is regarded as the birth year of the modern car when German inventor Karl Benz patented his Benz Patent-Motorwagen. Cars became widely available in the early 20th century. One of the first cars accessible to the masses was the 1908 Model T, an American car manufactured by the Ford Motor Company.

P0351 Ignition Coil A Primary/Secondary Circuit Malfunction

An ignition coil is an inductive component that converts electrical energy into a high-voltage spark used to ignite fuel in an internal combustion engine. P0351 is a diagnostic trouble code (DTC) for “Ignition Coil A Primary/Secondary Circuit Malfunction”. This can occur in any vehicle make and model equipped with multiple ignition coils, such as those found in most modern cars or trucks. Symptoms of this issue can include poor fuel economy, stalling engine or misfiring cylinders, and a variety of unusual noises or smells coming from your engine bay. To diagnose this issue properly, use a visual inspection and voltage test to identify any problems with your ignition coil A primary/secondary circuit malfunctioning.

Poor Fuel Economy

A malfunctioning ignition coil can cause poor fuel economy due to incomplete combustion caused by misfiring cylinders or lack of spark energy reaching your spark plugs. This will cause unburned fuel to exit your exhaust pipe instead of being burned efficiently inside your combustion chamber which will reduce overall engine performance and result in poor fuel economy over time as more unburned fuel goes out with each exhaust stroke. Additionally, this issue can also lead to higher emissions due to unburned fuel exiting your tailpipe which may lead to local environmental regulations being breached if left unchecked for too long.

Unusual Noises and Smells

Another symptom associated with this issue is unusual noises or smells coming from the engine bay when it misfires due to lack of spark energy reaching the spark plugs effectively lighting off each cylinder’s air-fuel mixture during its combustion stroke cycle. These symptoms should not be ignored as they can be indicators of serious damage that needs professional attention immediately before further damage occurs within your vehicle’s powertrain system components such as pistons and valves which would otherwise lead to expensive repairs later on down the line if left unchecked for too long without proper diagnosis or repair work being performed on it soon enough after these symptoms start manifesting themselves within your vehicle’s onboard diagnostic system’s error codes database log files report history records which are accessible via most reputable auto repair shops’ onboard scan tool device readings after hooking it up directly into your car’s onboard computer systems’ data port connection interface component ports located underneath the dashboard area near driver’s side door near kick panel area where ECU (Engine Control Unit) component box storing all relevant information related to current status report readouts gathered via sensors installed throughout entire powertrain system in order for technicians there be able diagnose any type problem accurately fast without having guess what wrong as well having access all pertinent information stored internally within ECU itself without having search elsewhere outside sources like parts supplier catalogues which may not always be reliable source info needed perform complete job correctly first time around without wasting customer’s money unnecessarily guessing wrong part first time around costing them more money than necessary have job done right at end day .

Diagnosing Ignition Coil A Primary/Secondary Circuit Malfunction

To diagnose this issue properly you need to perform both a visual inspection and voltage test on all relevant components involved with it such as wiring harnesses connected directly between ignition coils & their respective cylinder banks along with spark plug wires attached directly onto them respectively as well their ends connected onto spark plugs themselves so that you can make sure no loose connections anywhere causing potential short out between two points where electricity supposed flow through uninterrupted manner thus preventing normal operation occurring when key turned start position inside cab area while performing voltage test make sure no excess amount current flowing through any point original factory specs indicate otherwise otherwise could mean something else entirely wrong could easily overlooked technician working particular case thus causing unnecessary delay getting problem fixed ultimately leading customer being unhappy overall results not up par expected given situation was handled properly begin with before anything even started begin order get things back running again way supposed intended specific results desired end day outcome everyone looking forward achieving once again .

FAQ & Answers

Q: What is Ignition Coil A Primary/Secondary Circuit Malfunction?
A: Ignition Coil A Primary/Secondary Circuit Malfunction is a malfunction of the ignition coil that can cause engine misfiring and poor fuel economy. It can also produce unusual noises and smells.

Q: What are the signs of Ignition Coil A Primary/Secondary Circuit Malfunction?
A: The signs of Ignition Coil A Primary/Secondary Circuit Malfunction include engine misfiring, poor fuel economy, unusual noises, and smells.

Q: What causes Ignition Coil A Primary/Secondary Circuit Malfunction?
A: The causes of Ignition Coil A Primary/Secondary Circuit Malfunction can include poor maintenance, faulty wiring, and outdated parts.

Q: How do you diagnose Ignition Coil A Primary/Secondary Circuit Malfunction?
A: To diagnose Ignition Coil A Primary/Secondary Circuit Malfunction, a visual inspection should be conducted to identify any potential issues, followed by a voltage test to confirm the presence of an issue.

Q: How do you fix Ignition Coil A Primary/Secondary Circuit Malfunction?
A: To fix Ignition Coil A Primary/Secondary Circuit Malfunction, faulty wiring should be replaced and parts should be updated as needed. Poor maintenance should be addressed to ensure that the issue does not recur.

In conclusion, a malfunction in the primary/secondary circuit of the P0351 ignition coil can cause serious engine problems, such as misfires, hesitations and rough idling. If any of these issues occur, it is important to have the system tested and inspected for potential faults. With proper diagnosis and repair, a malfunctioning P0351 ignition coil can be fixed and the car can be returned to its normal running condition.

Author Profile

Carl Frisch
Carl Frisch
With more than 30 years in the bicycle industry, I have a strong background in bicycle retailing, sales, marketing and customer service. I have a passion for cycling and a dedication to excellence. As a manager, I worked diligently to increase my capabilities and responsibilities, managing up to eleven mechanics (at Palo Alto Bicycles) and later as a working partner in my own store.

As the shop owner of Spoke n’ Word Cycles in Socorro, NM, the success of the mission was my responsibility, which I pursued passionately since we opened in 2003 through the spring of 2011. I am adept at managing owned and loan inventory, preparing weekly & annual inventory statements, and managing staff. The role as managing partner also allowed me tremendous freedom. I used this personal freedom to become more deeply involved in my own advancement as a mechanic, to spearhead local trail building, and advocating for cycling both locally and regionally.

As a mechanic, I have several years doing neutral support, experience as a team mechanic, and experience supporting local rides, races, club events. I consistently strive to ensure that bicycles function flawlessly by foreseeing issues and working with the riders, soigners, coaches and other mechanics. Even with decades of experience as a shop mechanic and team mechanic, and continue to pursue greater involvement in this sport as a US Pro Mechanic, and UCI Pro Mechanic.

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