This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.
P0355 is an OBD-II Code that refers to Ignition Coil B Primary/Secondary Circuit Malfunction
A P0355 code is caused by an ECM (Engine Control Module) receiving a signal from the PCM when one of these ignition coils (in this instance, coil B) has a wiring problem, the engine will not run correctly and may issues with combustion.
Common causes for this code include:
- A faulty Engine Control Monitor
- A fault with the ignition coil or its associated wiring, including the connector.
- This could be caused by poor connection, unplugged connectors, corroded terminals, etc…
- Shorting wires to/from Engine Control Module(s)
- Faulty spark plugs (open circuit ground electrode)
- Spark plug wire damage due to excessive heat or chafing on other wiring
- Carbon buildup in the engine's air passageways or throttle body
The symptoms of a P0355 code are:
- The Check Engine Light comes on
- The engine may start to run unevenly
- Misfiring or hesitation under load
- Possible engine rough idle
- Increased fuel consumption
To diagnose a P0355 DTC code, a technician would:
- Scan for codes in the ECM and look at the freeze frame data for failure.
- Check for signs of the ignition coil being burned, melted or excessively hot
- Inspect terminals and wiring harnesses for chafing, bare wires that may short to each other or parts.
- Perform a test drive to determine if the code returns or other codes are found.
- Check for fuel pressure and ensure it is within specifications for this particular vehicle.
- Check the air intake and throttle body to ensure that there is no carbon build up or restrictions
- Inspect the ECM for damage due to over-powered voltage spikes.
- Inspect spark plugs, inspect spark plug wires from inside boot/cover, check resistance of coils and ignition modules.
The following are some of the most common mistakes that a technician may make when diagnosing a P0355 code:
- Sometimes technicians will replace the coil(s) and/or ignition module(s) without confirming or checking other causes such as a faulty or shorted wiring harness, damaged ECM, faulty spark plugs, etc
- A technician may skip testing for fuel pressure and verifying that it is within specifications set by the manufacturer of this vehicle.
- If there are no symptoms present and all electrical components tested out ok, then a misfire may be blamed on an ignition problem when it could be another issue such as bad gas mileage due to carbon build up in intake valves.
How serious is this?
A P0355 code is not usually serious. Although it may cause some issues with the vehicle idling, running rough or misfiring. It could indicate a lack of performance on the car and could lead to more serious issues such as catalytic converter damage or severe engine damage if ignored for too long.
What repairs can fix the code?
The following are solutions that may fix this problem:
- Cleaning the throttle body
- Replacing the spark plugs
- Replace all wires, connectors and other parts involved with this problem area
- Checking for fuel pressure that is within specifications set by the manufacturer of this vehicle.
- Repair or replace damaged wiring harnesses
- Repair or replace damaged PCM (ECM)
A P0355 is related to and may be accompanied by the following codes:
P1341, P1342, P1343, P1344 - Open or short Circuit or coil primary/secondary circuit
In conclusion, the P0355 code is a generic trouble code that means the computer has detected an issue with one of the ignition coil primary/secondary circuits. This could be caused by wiring harness, ignition coil or PCM (ECM) damage. If you have a P0355 code and it is accompanied with other codes such as P1341, P1342 etc., then replacing the spark plugs and spark plug wires may not fix the problem because there might be something else wrong such as corroded terminal on spark plugs or damaged module(s). You should always check all possible causes for this type of code before replacing parts.