The OBD2 code P2305 indicates a malfunction in the secondary circuit of Ignition Coil “B.” This specific error points to issues such as insufficient ionization or a weak spark, which can lead to engine misfires, poor engine performance, and increased emissions. Typically affecting one of the engine’s cylinders, this code is a signal that the coil’s ability to ignite the air-fuel mixture in the combustion chamber is compromised, necessitating prompt diagnostic and repair actions.
P2305 quick overview
| Meaning | P2305: Ignition Coil B Secondary Circuit Insufficient Ionization |
| Is it serious? | Yes, it can cause misfires, decreased fuel efficiency, and potential damage to the catalytic converter if not addressed. |
| Possible causes | – Faulty ignition coil – Poor electrical connection in the coil circuit – Use of non-OEM (Original Equipment Manufacturer) parts – Faulty engine control module (ECM) – Damaged or worn spark plugs and wires |
| How to diagnose? | Check for aftermarket parts and consider replacing with OEM components. Inspect the ignition coil and wiring for damage or corrosion. Test the electrical connections to the coil for tightness and cleanliness. Evaluate the condition of spark plugs and wires, replacing if necessary. Assess the engine control module for possible reprogramming or replacement. |
P2305 Meaning
When you encounter the P2305 code, think of it as your car’s way of saying there’s a weak link in the electrical chain leading to one of the spark plugs. This coil “B” is crucial for zapping the right amount of electricity to the plug so it can light up the fuel in the engine.
If the spark isn’t strong enough, you’ll feel it as the engine stumbles or misfires, especially under load or when starting. It’s often a sign to check not just the coil itself but also the parts connected to it, like the spark plugs and their wires, to ensure everything’s in top shape. Using parts straight from the car’s manufacturer rather than generic ones can often nip these issues in the bud.
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How to fix P2305 – learn from mechanics
I looked into P2305 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.
Case #1: Chrysler
Vehicle Information 2003 Chrysler PT Cruiser GT 2.4L
Issue + Repair History
- Came in with a misfire on cylinder #3
- Replaced ignition wires and coil pack
- Symptoms recurred during highway driving after 10 minutes, check engine light on, loss of power
- Replaced coil again
- Symptoms persisted after clearing codes
Other OBD2 Codes + Test Results
- P0303: Cylinder 3 Misfire
- P2305: Ignition Coil #2 Secondary Circuit Insufficient Ionization
- P2302: Ignition Coil #1 Secondary Circuit Insufficient Ionization
- Voltage at idle: 14.23V
Mechanic Suggestions
- Check for head gasket leaks and injector harness issues
- Consider switching to a factory OEM coil instead of aftermarket
- Investigate the fuel rail for debris due to high mileage
- Verify timing belt synchronization and condition of cam/crank sensor
- Suggest using a new Chrysler coil, as aftermarket coils may be unreliable
- Possibility of a bad PCM or needing reflash
Final Fix
- Replacing the aftermarket coil with a OEM coil from Chrysler resolved the issue permanently
Case #2: Chrysler
Vehicle Information 2003 Chrysler PT Cruiser Touring 2.4L
Issue + Repair History
- Initially presented with multiple misfires and P2305 code
- Replaced coil, plugs, and wires with aftermarket parts
- Symptoms recurred during extended driving, causing loss of power and rough idle
- Only code to return was P2305
Other OBD2 Codes + Test Results
- P2305: Ignition Coil ‘B’ Secondary circuit
Mechanic Suggestions
- Try an OEM coil as aftermarket coils may not be reliable
- Check for broken coil driver wire, particularly if issue resolves when the car is cold
- Test battery and alternator output to ensure proper voltage supply
- Consider the possibility of a faulty engine coil capacitor affecting ionization
Final Fix
- Replacing the aftermarket coil with an OEM coil resolved the issue permanently
Case #3: Jeep
Vehicle Information 2004 Jeep Liberty Sport 3.7L
Issue + Repair History
- Engine starts but races up to the rev limiter (4000rpm) and then cuts out
- Suspected large intake air source due to possible crack in the plastic upper plenum
- Codes: P0522 (oil pressure sensor), P2305 (coil 2 ionization), P2308 (coil 3 ionization)
- Smoke test performed to check for intake leaks
- Identified hole in the plastic plenum at the rear, likely caused by backfiring due to worn spark plugs or malfunctioning detonation sensors
- Repaired by replacing plenum, spark plugs, coils, detonation sensors, PCV valve, and tubing
Other OBD2 Codes + Test Results
- P0522: Oil pressure sensor
- P2305: Coil 2 ionization
- P2308: Coil 3 ionization
Mechanic Suggestions
- Smoke test intake for leaks or pressurize and use soapy water to detect leaks
- Monitor timing advance during startup to check for abnormal idle control
- Inspect IAC motor for debris and check for a popped-off plastic casting in the rear of the intake manifold
- Replace spark plugs as a starting point for diagnosis
Final Fix
- Replaced plenum, spark plugs, coils, detonation sensors, PCV valve, and tubing to address intake air leak and related issues caused by poor maintenance
How to diagnose P2305
I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.
| Diagnostic Step | Explanation |
|---|---|
| Check for aftermarket parts | Ensure all components are OEM to avoid compatibility and performance issues. |
| Inspect the ignition coil and wiring | Look for signs of physical damage, wear, or corrosion that could impair function. |
| Test the electrical connections | Verify that connections are secure and free of corrosion for optimal electrical flow. |
| Evaluate the condition of spark plugs | Replace worn or damaged spark plugs that could contribute to ignition issues. |
| Assess the engine control module | Consider if the ECM needs reprogramming or replacement to correct the ignition sequence. |
In the service cases reviewed, P2305 was effectively resolved by replacing aftermarket ignition coils with OEM parts, underscoring the importance of using manufacturer-recommended components for repair. Issues like loose connections and damaged intake components were also identified, highlighting the need for comprehensive diagnostics beyond the ignition system to address underlying causes of misfires and poor engine performance.
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
- How to use an OBD reader
- Introduction to a Bi-directional Scan tool
- OBD scanner buyer’s guide + discounts
I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko