Cylinder 8 Misfire Detected
Table of contents
P0308 HUMMER Possible Causes
- Faulty spark plug 8
- Clogged or faulty fuel injector 8
- Faulty ignition coil 8
- Fuel injector 8 harness is open or shorted
- Fuel injector 8 circuit poor electrical connection
- Ignition coil 8 harness is open or shorted
- Ignition coil 8 circuit poor electrical connection
- Insufficient cylinder 8 compression
- Incorrect fuel pressure
- Intake air leak
How do I fix code P0308 HUMMER?
Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector’s pins.
Tech Notes
- The P0308 code means that the cylinder 8 is misfiring or is randomly misfiring. Start by checking for intake leaks and if no leaks are found the next step is to replace the spark plugs on cylinder 8. If the problem persists more tests need to be done to diagnose the problem, see “Possible Causes”.
Cost of diagnosing the P0308 HUMMER code
The cost of diagnosing the P0308 HUMMER code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle’s make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.
Possible Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Lack/loss of power
- Hard start
- Engine hesitation
P0308 HUMMER Description
The Engine Control Module (ECM) uses information from the crankshaft position sensor and the camshaft position sensor to determine when an engine cylinder misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM can detect inpidual cylinder misfire events.
Extreme cylinder misfire events can cause catalytic converter damage. The malfunction indicator lamp (MIL) will flash when the conditions for catalytic converter damage are present. The Diagnostic Trouble Codes (DTC) P0308 correspond to cylinders 8. When the ECM detects that one or more specific cylinders are misfiring, the DTC for the respective misfiring cylinder will set, and up to 2 of the corresponding fuel injectors are disabled for a minimum of 30 s. The ECM will then re-enable the fuel injector and, after approximately 200 engine revolutions, will determine if the misfire is still present. If the misfire is still present, the ECM will disable the fuel injector again repeating the process. If the misfire is not present, the fuel injector will remain enabled by the ECM. In Spark Ignition Direct Injection (SIDI) system applications, if a fuel injector fault DTC is set during a misfire event, the ECM will not re-enable the injector.
