STEP 4: Checking For Trouble Codes
Whenever I diagnose I no-start condition, I usually don't check for trouble codes because most no-start problems usually don't leave a trouble code.
But in this case I ended up hooking up my generic scan tool because all of my test results were pointing to a defective crankshaft position sensor and I was wanting to know if there was a crankshaft position sensor trouble code stored in the fuel injection computer's memory.
To my surprise there was a camshaft position sensor trouble code instead of a crankshaft position sensor trouble code. It was a OBD2 P0340 trouble code. My next step was to check the camshaft and crankshaft position sensors but at that particular moment I didn't have the necessary wiring diagram.
So, I told my friends that I needed to run down to a friend's auto repair shop to get the wiring diagram to test the cam and crank sensors and that this meant coming back the next day.
STEP 5: Testing The Cam And Crank Position Sensors
Since my previous tests had confirmed a lack of spark and fuel injector pulses, it was starting to become pretty obvious the crank sensor was bad. Why? Because previous experience has shown me that when the crank sensor fails, the fuel injection computer will not activate the ignition coils nor the fuel injectors.
It's also been my experience that when the fuel injection computer registers a cam or a crank sensor trouble code, you have to test them both. There have been times I've gotten a trouble code for a cam sensor and it turned out to be a failed crank sensor (and vice-versa). So, I've gotten in the habit of testing them both to make sure I'm gonna' replace the one that's bad and causing the problem.
On the 2002 1.8 Nissan Sentra, testing the crankshaft and camshaft sensor is pretty easy. The only hard part is getting access to the crankshaft position sensor, since you do have to remove the air filter assembly from the engine to be able to access the connector from the top of the engine.
To test the camshaft and crankshaft position sensors, I followed the instructions in these 2 tutorials:
- How To Test The Camshaft Position Sensor (2000-2002 1.8L Nissan Sentra).
- How To Test The Crankshaft Position Sensor (2000-2002 1.8L Nissan Sentra).
Well, it turned out that the fuel injection computer was right all along since my tests confirmed that the camshaft position sensor was stuck producing 9 Volts DC and never switching the signal down to 0 Volts.
I ran down to the auto parts store and bought the camshaft position sensor, came back and replaced it and the engine started!
My friends were pretty happy! And so was I, since I dodged a bullet (by not having to replace the fuel pump).
More 1.8L Nissan Sentra Tutorials
You can find a complete list of tutorials for you Nissan 1.8L equipped car here: Nissan 1.8L Index Of Articles.
Here's a small sample of the tutorials you'll find in the index:
- How To Test For A Blown Head Gasket (Nissan 1.8L).
- How To Test The Starter Motor (2000-2002 1.8L Nissan Sentra).
- How To Test Engine Compression (Nissan 1.8L).
- How To Test The 2000-2002 Nissan Sentra 1.8L MAF Sensor (at: easyautodiagnostics.com).
If this info saved the day, buy me a beer!