P0307: Cylinder 7 Misfire Detected
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Short careful trips only - avoid heavy throttle until repaired.
Symptoms
- Flashing check engine light
- Engine shake
- Loss of power
Likely causes, most common first
- Coil or plug on cylinder 7
- Injector fault
- Vacuum leak on that runner
- Stuck cylinder deactivation lifter
Read P0307 yourself before paying for diagnosis
A basic Bluetooth OBD-II scanner ($20-40) plugs into the port under the dashboard and shows this code with live sensor data on your phone - useful both for confirming the fix and for talking to a shop from an informed position.
What is going on and how it gets diagnosed
P0307 requires an eight-cylinder engine, so this code belongs almost entirely to full-size trucks, SUVs and rear-drive V8 sedans. On those engines cylinders are usually numbered front to back down each bank, which puts cylinder 7 near the rear of one side - close to the firewall and, on trucks, often buried under the brake booster or heater box.
On V8 engines with cylinder deactivation, a rear-bank misfire deserves an extra check: a deactivation lifter that fails to reactivate produces exactly this code, and no quantity of ignition parts will fix it. Read oil pressure and lifter behaviour before going to the parts counter.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Owner reports mentioning P0307
“Another GM truck AFM failing. It failed at 70,000 miles causing P0307 cylinder 7 misfire. No aggressive driving just commuting to work. Truck just got done with a new oil change. It's another to add to the hundreds/thousands seen on Reddit threads of all 5.3/6.2 AFM/DFM that this organization turns a blind eye to.”2015 GMC Sierra 1500 · Mar 2026
“Code p0307 misfire on cylinder 7. Have gotten code 3 times in last month. Lights on dash and reduced power. Less than 50k miles when first occurred. Turn off and back on all lights gone except for engine light which goes off in a day then runs fine. Dealer quoted $3k+ to replace injectors. $60k+ for a new vehicle it should last more than 2 years and 50k miles. 5 yr 60k mile engine and power train warranty but they pick and choose what components to cover. After looking online I see many owners with same issues. Some with hardly any miles. Other recalls done with different motor sizes. HELP!!!”2022 Chevrolet Silverado 1500 · Aug 2025
“check engine light came on and the code was cylinder 7 misfire 'code p0307'. it was replaced the first time and only lasted less than two months. the same code came up again and when they put a new one in they had to tow it back because it failed not even 30 minutes later.”2014 Chevrolet Silverado 1500 · Mar 2024
Show 3 more owner reports
“62,000 MILES. P0307 error. Replaced spark plugs, coil. head removal, lifter replaced and now another bad lifter. Faulty Active Fuel Management Lifter (AFM Lifters) that results in the Valve Train Defect. In shop for lifter repairs.(2nd time) Cost is $3000. Well maintained truck with all required service completed. Never even towed anything. Vehicle should not have these issues with this low mileage.”2015 GMC Sierra 1500 · May 2022
“Experienced error code of P0307 after vehicle backfired while on highway. Check engine light and stabilitrak lights immediately turned on and vehicle was shaking violently. Immediately took vehicle to an independent shop to have it looked at. After running diagnostics, pressure tests, and bore scope. It has been determined that piston in cylinder 7 is a complete loss and has a 0 pressure reading. From talking with shop owner he said he sees this issue quite often with GM vehicles due to DOD or AFM (active fuel management) that GM has on their engines. I'm at just shy of 67k miles, out of warranty, and needing to replace the engine.”2016 GMC Sierra 1500 · Aug 2021
“Truck started missing and backfiring when accelerating from a stop, lost power assist to brakes, limped 1/2 mile to my house . Engine was clattering , missing, stalling and backfiring. Check engine light on code p0307. Broke #7 valve spring(intake) , lost keepers, dropped valve , which piston hit, ford dealer say it needs an engine for $10,300.00 and no coverage at 69,000. Broken valve springs are a known problem . Dangerous when you lose power assist to brake pedal because of no vacuum. Request ford service to assist because springs are defective”2015 Ford F-350 SD · Sep 2019 · 69,000 mi
Cars that report P0307 most often
Based on mentions of this code in NHTSA owner complaints.
Frequently asked questions
Can I drive with P0307?
Short careful trips only - avoid heavy throttle until repaired.
How much does it cost to fix P0307?
Typical US repair costs range from $20 for the simplest fix (spark plug) to $600 in the worst case. The right number depends on which cause your car has - see the causes list.
Related codes
The codes closest to P0307. They often appear together, and telling them apart is usually what narrows the diagnosis.
Definition per SAE J2012 standard nomenclature. Symptoms, causes and costs are editorial guidance - always confirm with a diagnosis of your specific vehicle.