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AutoCodes - Generic - P0303

P0303 Code - Cylinder 3 Misfire Detected

- Code Popularity: 308,155 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
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What are the Possible Causes of the DTC P0303?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
  • Faulty Spark Plug #3
  • Clogged or faulty Fuel Injector #3
  • Faulty Ignition Coil #3
  • Fuel Injector #3 harness is open or shorted
  • Fuel Injector #3 circuit poor electrical connection
  • Ignition Coil #3 harness is open or shorted
  • Ignition Coil #3 circuit poor electrical connection
  • Insufficient cylinder 3 compression
  • Incorrect fuel pressure
  • Intake air leak
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How to Fix the DTC P0303?

Review the 'Possible Causes' mentioned above and visually examine the corresponding wiring harness and connectors. Ensure to check for any damaged components and inspect the connector pins for signs of being broken, bent, pushed out, or corroded.

Code Tech Notes

The P0303 code means that cylinder 3 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 3. If the problem persists more tests need to be done to diagnose the problem, see "Possible Causes".













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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0303 code, it typically requires 1.0 hour of labor. The specific diagnosis time and labor rates at auto repair shops can differ based on factors such as the location, make and model of the vehicle, and even the engine type. It is common for most auto repair shops to charge between $75 and $150 per hour.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)
  • Lack/loss of power
  • Hard start
  • Engine hesitation

Code P0303 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 individual 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) P0303 correspond to cylinders 3. 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.
OBDII Code P0303 - Cylinder 3 Misfire Detected - AutoCodes.com
P0303 Code - Cylinder 3 Misfire Detected

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