P0308
Cylinder 8 Misfire Detected
The appearance of the standard OBD2 trouble fault code P0308 is an indicator that your vehicle ECU triggered a threshold alert for "Cylinder 8 Misfire Detected". Understanding the root component breakdown helps avoid expensive diagnostic fees.
Driver's Summary
A P0308 fault code points directly to a problem with cylinder 8 misfire detected that the ECM has confirmed over multiple drive cycles. The most common signs are severe engine vibration, flashing engine light, stalling. This is not a code to ignore — the underlying fault can rapidly worsen and lead to costly repairs if driving continues.
Symptoms
Severe engine vibration, flashing engine light, stalling
Common Causes
- Bad spark plug
- Faulty ignition coil
- Clogged or dead fuel injector
- Burnt exhaust valve
How to Fix
- 1 Replace spark plug
- 2 Replace ignition coil pack
- 3 Test and replace fuel injector
- 4 Perform cylinder compression test
Technical Explanation
P0308 is stored after the control module confirms the fault over multiple ignition cycles, ruling out transient electrical noise as the cause. For injector-specific codes, the ECM monitors the injector control circuit voltage drop during each pulse; a shorted or open injector presents a characteristic resistance signature that differs measurably from a healthy unit. After two failed drive cycles, the code transitions from a pending to a confirmed DTC, and the PCM activates the MIL. Clearing the code without repairing the fault will result in re-illumination within one to two complete drive cycles.
Is It Safe to Drive?
This fault carries real mechanical risk. The root causes — including bad spark plug — can trigger a chain reaction of component failures if the vehicle continues to be driven. Have it towed or drive directly to a shop without delay.
Mechanic's Pro Tip
For P0308, test the solenoid's coil resistance with a multimeter before ordering parts — most solenoids should read between 14 and 40 ohms; an open (infinite resistance) or short (near zero) confirms it's failed electrically. Also verify the PCM is commanding the solenoid by backprobing the connector with a test light during the relevant operating condition — if there's no command signal, the fault is in the PCM or wiring, not the solenoid itself.
Related Fault Codes
Frequently Asked Questions
What does OBD2 code P0308 mean?
OBD2 code P0308 refers to Cylinder 8 Misfire Detected. The appearance of the standard OBD2 trouble fault code P0308 is an indicator that your vehicle ECU triggered a threshold alert for "Cylinder 8 Misfire Detected". Understanding the root component breakdown helps avoid expensive diagnostic fees.
What are the most common symptoms of DTC P0308?
Drivers experiencing code P0308 typically report: Severe engine vibration, flashing engine light, stalling.
Is it safe to drive with trouble code P0308 active?
This fault carries real mechanical risk. The root causes — including bad spark plug — can trigger a chain reaction of component failures if the vehicle continues to be driven. Have it towed or drive directly to a shop without delay.
How much does it cost to fix code P0308?
The estimated repair cost for P0308 ranges from $50 to $2000 USD. Coil/Plug: $150; Valve job: $1,500 - $2,000
Coil/Plug: $150; Valve job: $1,500 - $2,000
Need Professional Diagnostic Assistance?
Always verify sensor signals and wiring integrity with an OBD2 scanner before purchasing replacement parts.
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