P0303 Nissan 3.5L – How To Test VQ35 Ignition Coil
The P0303 Nissan OBDII Trouble Code is a multiple engine misfire condition and one that can be detrimental to your engine as well as difficult to track down and diagnose. Although the trouble code of P0303 directly refers to Cylinder 3 misfire in particular, this trouble code can also be accompanied by several other misfire codes that can also be intermittent. To make things worse, any number of issues can lead to misfire conditions from fuel or air inconsistencies to electrical or ECU problems.
The Nissan / Infiniti 3.5L VQ35DE six cylinder engine has it’s own checks and procedures for engine misfire. The logic in the VQ35DE checks for engine misfire one of two different distinct ways. If the misfire condition is severe enough to cause the crank position sensor (CKP) to vary, the ECU will know that a misfire condition exists. There are two ways the VQ35 diagnoses and detects the misfire, one trip detection logic and two trip detection logic.
Today I’ll be showing you how to diagnose and check each condition of VQ35DE engine misfire in a 2006 Infiniti G35 coupe.
One Trip Detection
When the ECU detects a misfire severe enough to damage the vehicle’s three way catalyst (TWC) due to excessive exhaust gas temperatures (EGT), the Malfunction Indicator Lamp (MIL) will blink. When the MIL blinks the ECU will begin to monitor the crankshaft position sensor (CKP) signal every 200 engine revolutions for any changes to indicate engine speed variation.
The MIL will turn off if the severity of the misfire decreases, resulting in lower EGT and no damage to the TWC. These parameters only exist for the duration of the first trip or first trip where the incident of misfire occurred.
Two Trip Detection
The second of the two methods in which the VQ35DE can recognize engine misfire is two trip detection logic. This logic dictates that when misfire is detected but no damage occurs to the TWC, the ECU will monitor the CKP sensor signal every 1000 engine revolutions. This will light the MIL and can recognize the misfire in any one cylinder or on multiple cylinders.
- P0300 – Cylinder Misfire Detected Random Cylinders
- P0301 – Number 1 Cylinder Misfire Detected
- P0302 – Number 2 Cylinder Misfire Detected
- P0303 – Number 3 Cylinder Misfire Detected
- P0304 – Number 4 Cylinder Misfire Detected
- P0305 – Number 5 Cylinder Misfire Detected
- P0306 – Number 6 Cylinder Misfire Detected
Here are a few different reasons for engine misfire in the 3.5L Nissan VQ35, please click on any one of the links for more information. Today we are looking at the faulty ignition coil and I’ll show you how to test your ignition coil in cylinder #3.
- Improper Spark Plug Gap
- Faulty Spark Plugs
- Intake manifold leak
- Fuel Injector Leak
- Incorrect Fuel Pressure
- Faulty Ignition Coil
- Bad Compression
Faulty Ignition Coil
Before beginning this test make sure you are in a well ventilated area as gas fumes may exit from the cylinder. To begin the test, you will need to undo the 10mm bolts that secure the harness on the passenger side as this OBDII trouble code is for cylinder 3.
Cylinder #3 is located on the passenger side of the motor, and can be accessed by removing this harness clip held on by the 10mm bolt. Remove this bolt and set the harness to the side to unplug your cylinder #3 ignition coil connector
Unplug the ignition coil connector, and remove the ignition coil by undoing the 10mm bolt and using a multimeter measure the resistance values Ω between the pins shown below.
Check the resistance values on the ignition coil terminals, not the harness. The ignition coil should be tested at 25°C (77°F) and should not be hot when conducting this resistance test.
- Pins 1 and 2 – Except 0 or ∞
- Pins 1 and 3 – Except 0
- Pins 2 and 3 – Except 0
If the resistance values fall outside of that range, your ignition coil is faulty and should be replaced. The part numbers for this ignition coil are 22433-AL61C and 22448-AL61C for Infiniti OE and 22433-AL615 and 22448-AL615 for Nissan OE. Use any replacements to fix your P0303 Nissan check engine light and clear your trouble codes.
If your coil checks out here, check the operation of your ignition coil by unplugging your fuel pump relay. Start the engine and wait for the car to stall because the fuel pump is no longer operating.
After the engine dies, continue to crank the engine over a few times to ensure that fuel pressure has been released. Turn the key to the “OFF” position and unplug all the ignition coil connectors except for the coil you are testing (Cylinder 3 in this example)
Have a friend crank over the motor while you hold the opening of the ignition coil roughly 10mm away from a grounded part of your engine. There should be spark that is conducted between the ignition coil and your motor. Be careful not to get an electrical shock while checking, because the electrical discharge voltage becomes 20kV or more.
If you VQ35 ignition coil checks out here, move onward to P0303 – Nissan 3.5L – Check Spark Plug Gap