P0320: Ignition/Distributor Engine Speed Input Circuit
What Does P0320 Mean?
P0320 is a diagnostic trouble code indicating: Ignition/Distributor Engine Speed Input Circuit. This code relates to the ignition system system. It has been reported in NHTSA complaints across 2 different vehicle models.
Engine misfires are detected by monitoring crankshaft rotational speed variations. Each cylinder's power stroke produces a characteristic acceleration pattern. When a cylinder fails to fire, the crankshaft decelerates during that cylinder's stroke. The ECM identifies which cylinder misfired and how often. P0313-P0399 codes cover extended misfire monitoring including lean misfire detection, knock-related ignition faults, and secondary ignition monitoring. A flashing check engine light during active misfires is an emergency — raw unburned fuel enters the catalytic converter, potentially destroying it.
Symptoms of P0320
- ⚠️ Check engine light on (may flash during active misfire)
- ⚠️ Engine misfiring — rough idle, stumbling, shaking
- ⚠️ Loss of power during acceleration
- ⚠️ Increased emissions and fuel consumption
- ⚠️ Catalytic converter damage if ignored
- ⚠️ Possible engine vibration at idle
Common Causes
- 🔍 Worn or fouled spark plugs
- 🔍 Faulty ignition coil
- 🔍 Vacuum leak causing lean misfire
- 🔍 Fuel injector issue (clogged, leaking, or electrical)
- 🔍 Low compression (worn rings, burned valve, head gasket)
- 🔍 Incorrect ignition timing
P0320 Reports by Year
Real Owner Reports
From NHTSA complaint database — actual owner descriptions.
"NOVEMBER 2009 AT 50,000 MILES HAD RADIATOR AND WATER PUMP REPLACED UNDER WARRANTY BY DEALER. MARCH 2010 A RECALL ON THE TRANSMISSION PCM CARD WAS INSTALLED. HAD TO NOTIFY DEALER THREE TIMES THAT THE TRANSMISSION WAS NOT FUNCTIONING WELL, DEALER REBUILT TRANSMISSION. JULY 2010, 67000 MILES THE THE"
— Ford Explorer owner, 07/15/2010
"2008 FORD FOCUS DOES NOT ACCELERATE PROPERLY OR STALLS RANDOMLY. ON MULTIPLE OCCASIONS I WAS IN TRAFFIC ON BOTH CITY STREETS AND HIGHWAYS AND NEARLY GOT HIT MORE THAN ONCE. I HAD THE PCM REPLACED BY A CERTIFIED FORD MECHANIC IN 11/14, IT HAD A TWO YEAR WARRANTY. IN 1/16 IT BEGAN DOING THE SAME TH"
— Ford Focus owner, 05/12/2016
Source: NHTSA Complaints Database
Most Reported Vehicles for P0320
Based on NHTSA owner complaint data.
| # | Vehicle | Reports |
|---|---|---|
| 1 | FORD EXPLORER | |
| 2 | FORD FOCUS |
Diagnostic Tips
- Check misfire counters in Mode 6 data — identifies which cylinder(s) are misfiring most
- Swap ignition coil to another cylinder — if misfire follows, coil is bad
- Check spark plugs — worn electrode, fouled with oil or carbon, cracked insulator all cause misfires
- Perform compression test on affected cylinder(s) — low compression means mechanical issue
Common Mistakes to Avoid
- ❌ Replacing coils without checking spark plugs — a worn plug will kill a new coil
- ❌ Ignoring a flashing check engine light — this means severe misfire that's damaging the catalytic converter NOW
- ❌ Replacing ignition parts when the misfire is caused by a vacuum leak or low compression
Frequently Asked Questions
What does a flashing check engine light mean?
Can misfires damage my engine?
Why does my car misfire only when cold?
What To Do Next
Possible Fixes
- 🔧 Replace spark plugs
- 🔧 Replace ignition coil(s)
- 🔧 Repair vacuum leak
- 🔧 Clean or replace fuel injector
- 🔧 Engine mechanical repair (valves, rings, gasket)
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Click your make and model for real owner reports and common causes specific to your vehicle.
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Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
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Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.