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.
Coil/Plug: $150; Valve job: $1,500 - $2,000