Technical Description of OBD-II Trouble Code
Malfunction in the Primary/Secondary Circuit of the Ignition Coil
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to OBD-II equipped vehicles (Hyundai, Toyota, Chevy, Ford, Dodge, Chrysler, etc.). Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
If your OBD-II vehicle has stored a code P0350, it means that the powertrain control module (PCM) has detected a problem with the primary and/or secondary circuits for one or more ignition coils or ignition coil packs.
Most OBD-II equipped vehicles use a coil-over-plug, distributorless ignition system. In this type of system, each cylinder has its own ignition coil that is connected to the spark plug using a short plug wire or silicon boot. The high-intensity spark required to fire the spark plug for each cylinder is created by battery voltage and a ground pulse from the PCM applied to a tightly wound induction coil (thousands of volts).
Systems that use coil packs function in a similar manner, except multiple spark plugs are fired from a coil pack that fires multiple cylinders in sequential order. This type of system typically uses longer high tension spark plug leads to transfer the high-intensity spark from the coil pack towers to the spark plugs.
Regardless of the type of ignition system, the PCM controls spark timing and function. The ignition coil releases a high-intensity spark when it receives a ground pulse from the PCM. If the PCM detects that any of the ignition coil circuits are not being completed when the ground pulse is applied, a code P0350 will be stored and a malfunction indicator lamp (MIL) may be illuminated.
Code Severity & Symptoms
A code P0350 is categorized as severe because it is likely to be accompanied by ignition misfire issues.
Symptoms of this code may include:
Causes
Possible causes for this code to be set are:
Diagnostic and Repair Procedures
To diagnose a code P0350, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable vehicle information source, such as ALL DATA (DIY).
Start your diagnosis of a code P0350 with a visual inspection of all ignition coil/pack wiring and connectors. Check for broken electrical connectors at the ignition coils or coil packs, as well as burned, broken, or corroded wiring. Rodent damaged wiring and corroded ignition coil electrical connector ends are common causes of a code P0350.
Next, connect the scanner to the vehicle diagnostic port and retrieve all the stored codes and freeze frame data. Record this information for later reference. Clear the codes and test-drive the vehicle to see if the P0350 is reset.
Use your vehicle information source to search for technical service bulletins (TSB) that may assist in your diagnosis. TSBs with matching symptoms and codes can be very helpful.
If there are cylinder-specific ignition coil primary/secondary circuit codes present, they may help you pinpoint the defective circuit or coil/pack. If there are no cylinder-specific codes present, you will need to determine which coil, coil pack, or circuit is malfunctioning. This can be done by testing the coils or coil packs for the correct level of Hertz when high-intensity spark is emitted. Alternatively, you can remove each spark plug wire/boot from the spark plug or unplug each coil pack electrical connector while the engine is running to identify the malfunctioning coil/pack.
Once you have located the faulty coil/pack, use the DVOM to test for battery voltage at the coil/pack connector when the ignition is on. If there is no voltage present, use the vehicle information source to find the voltage source and check for blown fuses or defective relays. Remember that blown fuses are a reaction to an electrical short and not the source of the malfunction. If all fuses and relays are good, use the DVOM to test individual circuits for continuity and resistance. Repair or replace circuits that do not comply with manufacturer’s recommendations.
If the voltage signal is present at the ignition coil/pack, test the coil connector for a ground pulse from the PCM. If no ground pulse is present, suspect a defective driver in the PCM if no other ignition codes are present.
Additional diagnostic notes:
