Fix P2308: Mechanic’s solutions that WORKED

The code P2308: Ignition Coil C Secondary Circuit points out a fault in the ignition coil C secondary circuit. This issue can lead to engine misfires and reduced power. It is advisable to address this code to prevent further damage to the vehicle.

P2308 quick overview

Meaning	P2308: Ignition Coil C Secondary Circuit
Is it serious?	This code can affect engine performance, causing misfires and reduced power. While not an emergency, it should be addressed to prevent further damage.
Possible causes	– Faulty ignition coil C – Damaged or corroded wiring in the ignition coil circuit – Poor electrical connections in the ignition coil circuit
How to diagnose?	Check Ignition Coil C: Test ignition coil C for proper functioning. Inspect Wiring: Examine the wiring in the ignition coil circuit for damage or corrosion. Check Electrical Connections: Ensure all electrical connections related to ignition coil C are secure. Swap Coils: Consider swapping ignition coil C with a known good coil to see if the issue follows. Clear Codes: Use a diagnostic tool to clear the fault code and monitor if it returns.

How to fix P2308 – learn from mechanics

I looked into P2308 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: Dodge

Vehicle Information:
2004 Dodge Grand Caravan SE 3.3L

Issue + Repair History:

• The van had a P2308 code for ignition coil #3 secondary circuit.
• Customer had changed plugs, wires, coil, and crank sensor; cylinders #3 & #6 were not firing.
• PCM was replaced but the problem persisted.

Other OBD2 Codes + Test Results:

• P2308 – Ignition coil #3 secondary circuit-insufficient ionization.
• Pin-out at coil showed coil control for 5&2 and 1&4 pulsing; 3&6 control was not.

Suggestions to Fix Issue:

• Check for a sync signal issue like a defective crank sensor or a shifted flywheel hub.
• Scope oxygen sensors closely as faulty ones can cause an ionization code for the coil.
• Check for a bad driver in the PCM, as a replacement PCM could cure the problem.
• Ensure the wire is checked all the way to the PCM’s pin connector for any faults.
• Consider if the coil resistance is low, it might have damaged your coil driver in the PCM.

Final Fix:
After sending the van to Dodge for testing, it was found that the coil was shorting the new computer. Both the coil and PCM were replaced, resolving the issue.

Case #2: Ram

Vehicle Information:
2015 Ram 1500 Laramie Limited 5.7L

Issue + Repair History:

• Initially repaired for a flat cam on #3; remanufactured engine installed.
• After 10k miles, experienced P0303, P2308 codes; replaced #3 coil.
• Recurred after 3k miles; replaced PCM and spark plugs.
• Continued issues after 1k miles; overlayed wire ckt K18, replaced PCM and coil.
• Persistent problems despite multiple repairs.

Other OBD2 Codes + Test Results:

• P2308: Ignition coil C secondary circuit.
• P0303: Misfire detected in cylinder #3.
• Continuity, grounding, and compression tests conducted.

Suggestions to Fix Issue:

• Replace all coils, not just the affected one.
• Check and potentially replace coil driver in PCM.
• Inspect and repair any damaged wiring.
• Consider OEM parts over aftermarket for compatibility.

Final Fix:

• Replaced #1 coil with a factory part after noting an anomaly in resistance.
• Addressed PCM issues and understood the importance of using OEM coils for compatibility with the PCM.

Case #3: Jeep

Vehicle Information:
2004 Jeep Liberty Sport 3.7L

Issue + Repair History:

• Codes: P0522 (oil pressure sensor), P2305 (coil 2 ionization), P2308 (coil 3 ionization).
• Symptoms: Engine starts, races to 4000rpm, then cuts out.
• Suspected excessive intake air due to a possible crack in the plastic upper plenum.
• Tested intake components but found no improvement.

Other OBD2 Codes + Test Results:

• P0522: Oil pressure sensor code.
• P2305: Ionization code for coil 2.
• P2308: Ionization code for coil 3.

Suggestions to Fix Issue:

• Smoke test the intake for leaks.
• Check and potentially replace spark plugs and coils.
• Monitor timing advance at startup to identify irregularities.
• Inspect IAC valve for debris.
• Examine the rear of the intake for a possible cracked plastic casting.

Final Fix:

• Discovered a hole in the plastic plenum at the rear.
• Replaced the plenum, spark plugs, coils, detonation sensors, and PCV valve and tubing.
• Engine ran well after repairs.
• Emphasized the importance of regular maintenance to the customer.

Case #4: Dodge

Vehicle Information:
2007 Dodge Charger 2.7L

Issue + Repair History:

• No start condition with DTCs for ignition coils on all cylinders.
• Scanner test revealed no signal from crank and cam sensors.
• Replaced crank and cam sensors with OEM parts.
• No spark despite sensor replacement.

Other OBD2 Codes + Test Results:

• P2302, P2305, P2308, P2311, P2314, P2317: Primary coil codes.

Suggestions to Fix Issue:

• Check ASD relay and potential PCM issue.
• Verify wiring to coils, cam, and crank sensors for power and ground.
• Use a scope to check CKP/CMP synchronization.
• Monitor primary coil pattern and current with appropriate tools.
• Check for proper circuits to sensors, especially shared 5V feed.
• Consider using advanced diagnostic tools like StartScan or WiTech for comprehensive diagnosis.
• Ensure that injectors are being pulsed.

Final Fix:

• Discovered a partially blown 20A fuse, not completely open but causing intermittent no-start.
• Replaced the fuse, and the engine started without issues.

Case #5: Chrysler

Vehicle Information:
2004 Chrysler Pacifica 3.5L

Issue + Repair History:

• Weaker spark at cylinder #3 compared to other cylinders.
• Spark is blue but not as strong as other cylinders.
• Spark does not jump as far when testing for spark at #3.
• Replaced #3 coil, all spark plugs, and #3 fuel injector.
• Checked wires from PCM to coil, found no problems.

Other OBD2 Codes + Test Results:

• P02308: #3 ignition coil code.

Suggestions to Fix Issue:

• Check for a wiring issue in the harness coming out of the PCM, especially for corrosion.
• Swap the #3 coil with another cylinder to see if the code follows the coil.
• Check the scope pattern to ensure that the kilovolt (kv) is the same in all cylinders.
• Inspect for a broken motor mount that could damage the harness.
• Consider replacing the PCM as coil drivers can fail in Chrysler PCMs.
• Invest in an HEI Test Plug for a more dependable spark test.

Final Fix:

• Replaced the PCM and reflash. The PCM controls the amount of fire and time duration, which resolved the issue.

Advice	Diagnostic Step
Check for wiring issues in the harness near the PCM.	Inspect the wiring harness for corrosion or damage.
Swap the suspect ignition coil with a known good one.	Determine if the issue follows the coil to another cylinder.
Verify the kilovolt (kv) output for consistency in all cylinders.	Use a scope to check and compare the kv in each cylinder.
Inspect for motor mount damage that could affect wiring.	Examine motor mounts for damage that may impact the wiring harness.
Consider replacing the PCM if other causes are ruled out.	If all other diagnostics fail, replacing the PCM may be necessary.
Invest in an HEI Test Plug for reliable spark testing.	Use an HEI Test Plug for more dependable spark testing.