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P0351 Severity
Identifying an OBD code is just the start of a complete diagnostic routine. Most trouble codes are caused by a sensor reporting a value that is out of range. Just replacing a sensor may not fix underlying issues. Be sure to understand the code, the part or system in your car that the code refers to, and the risks of delaying professional repair.
Proper diagnosis will save you time and money on unnecessary repairs.
Urgent codes indicate immediate action is necessary. These are urgent and significant malfunctions that can cause severe damage to the vehicle or harm the driver and passengers.
The ignition coil or coils are responsible for igniting the air/fuel mixture inside the combustion chambers. Without reliable performance from the ignition coil(s) the vehicle will stumble and misfire. The engine control module (PCM) has special transistors called "drivers" to turn the Ignition Coil(s) on an off. If the PCM cannot control the Ignition Coil, it will set code P0351.
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The ignition coil or coils are responsible for igniting the air/fuel mixture inside the combustion chambers. Without reliable performance from the ignition coil(s) the vehicle will stumble and misfire.
Code P0351 indicates there's an electrical problem in either the primary ( the computer side ) or the secondary ( the spark plug side ) of the Ignition Coil "A" Circuit.
When the code P0351 is set in the Powertrain Computer, it means that the Powertrain Computer or PCM is not seeing the proper electrical signals from the ignition coil(s) during normal operation. This can be caused by problems on either the primary (computer) side or the secondary (spark plug boot, spark plug wire and/or spark plug itself ) side.
When diagnosing a P0351 code, it is important to record the freeze frame information and then to duplicate the code setting conditions with a test drive. Pay close attention to the engine load, throttle position, RPM, and road speed. Road test the vehicle while viewing the misfire PID information on a data streaming scanner. If the vehicle is misfiring then you may have verified code P0351. Be sure to verify the the steadiness of the crank signal, because this can cause all kinds of downstream problems. If the vehicle deploys a multiple direct coil ignition system, locate the offending coil. Switch the entire coil and spark plug as an assembly with a known good cylinder, Clear the code(s) and go for a test drive. If the code re-sets and follows the coil assembly that was moved, then you may have verified the cause of the P0351 code. If the same cylinder sets the code, then perform a compression test on the offending cylinder and check for any vacuum leaks in its area with a good quality smoke machine. If the compression and smoke test results are good, then check the connector and wiring for that cylinder's coil circuit. If the connector and circuitry are good, then test the coil firing signal with a labscope, because the coil driver circuit may be defective.