If you suspect that the crankshaft position sensor is causing your 1.8L Nissan Sentra to not start, then this tutorial will help you to diagnose it using only a multimeter.
This multimeter test is a very accurate test that'll tell you if the crankshaft position sensor is bad or not.
Here are the contents of this tutorial:
- Symptoms Of A Defective Crankshaft Position Sensor.
- Circuit Descriptions Of The Crankshaft Position Sensor.
- TEST 1: Checking The Crankshaft Position Signal With A Multimeter.
- TEST 2: Making Sure The Crank Sensor Is Getting Power.
- TEST 3: Making Sure The Crank Sensor Is Getting Ground.
- Where To Buy The Crankshaft Position Sensor.
- More 1.8L Nissan Sentra Tutorials.
NOTE: If you need to test the camshaft position sensor, check out this tutorial: How To Test The Camshaft Position Sensor (2000-2002 1.8L Nissan Sentra).
Symptoms Of A Defective Crankshaft Position Sensor
Here is a basic list of the symptoms you are going to see when the crankshaft position sensor fails on your 2000, 2001, or 2002 1.8L Nissan Sentra.
- A trouble code P0340: Crankshaft Position Sensor A Circuit lighting up the check engine light.
- Car cranks but does not start.
- The fuel injection computer does not activate the fuel injectors (this is verified with a Noid light test).
- The fuel injection computer does not activate the ignition coils (this is verified with a spark tester).
- The fuel pump activates and sends the correct fuel pressure to the fuel injectors (this is verified with a fuel pressure gauge).
Circuit Descriptions Of The Crankshaft Position Sensor
The crankshaft position sensor is located behind the engine. To be a bit more specific: it's located right underneath the starter motor.
To be able to get access to it's electric connector, you need to remove the mass airflow sensor and intake air hose assembly.
Once you get to the crankshaft position sensor connector, you'll notice that it has 3 wires sticking out of it. Each wire has a specific job to do and in the table below you'll find a brief description of each:
|Crank Position Sensor (2000, 2001, 2002 1.8L Nissan Sentra)|
|2||RED||Crankshaft Position Signal|
|3||WHT||Power -12 Volts|
TEST 1: Checking The Crankshaft Position Signal With A Multimeter
The very first thing we're going to do is make sure that the crankshaft position sensor is creating a signal. Now to get into specifics, the crankshaft position sensor creates an ON/OFF voltage that you and I can measure with a multimeter in volts DC.
When the sensor is 'ON' it generates a voltage between 9 to 10 Volts DC. When the sensor is 'OFF', the voltage drops to 0 Volts DC.
The most common thing that I have seen, when the crank sensor fails, is that it will stay stuck producing only 9 to 10 volts without ever dropping down to zero volts (as the engine is manually turned from the crankshaft pulley).
So, in this test section we're gonna' connect a multimeter to the red wire of the crank sensor connector and then manually turn the engine and see if the sensor is good or not.
OK, let's get started:
Raise the front passenger side of your Sentra onto a jack stand (for safety).
Remove the front passenger side wheel and remove the plastic water splash guard (shield) that protects the crankshaft pulley and serpentine belt from water.
Disconnect the crank sensor from its electrical connector. As a safety precaution, disconnect all of the ignition coils from their electrical connectors.
NOTE: To gain access to the crank sensor connector, remove the air filter assembly and intake air duct assembly (it's easier to get to it from the top of the engine than from underneath).
Connect the red multimeter lead to the red wire of the crankshaft position sensor's connector. You'll need to use a tool like a wire piercing probe to connect the red test lead to the red wire.
You can see a what a wire piercing probe looks like here: Wire Piercing Probe.
Connect the connector back to the crankshaft position sensor. The crankshaft position sensor must be connected to its electrical connector for this test to work.
Set your multimeter to Volts DC mode and ground the black multimeter lead directly on the battery negative (-) terminal.
Slowly turn the crankshaft pulley by hand in a clock-wise direction while you keep you eyes on the multimeter once you have the multimeter set up. Do not use the starter motor to crank the engine and I want to emphasize slowly turning the crank pulley.
If the crank sensor is working correctly, the multimeter will register an On/Off voltage of 9-10 and 0 Volts DC as you manually turn the crankshaft. Off is when the multimeter displays 9.5 - 10 Volts DC and On is 0 Volts DC.
To be a little more specific: your multimeter will register 9 to 10 volts most of the time you're turning the crank pulley. When the crank sensor is activated (and if it's working correctly) by the pole piece on the crankshaft, then this voltage will go down to 0 Volts.
Let's take a look at what your test results mean:
CASE 1: The multimeter registered 9.5 to 10 Volts DC and the 0 Volt pulse as you manually turned the crankshaft pulley. This is the correct and expected test result and indicates that the crankshaft position sensor is working fine.
CASE 2: The multimeter DID NOT register the On/Off 9.5 to 10 Volts DC and 0 Volts pulse as you manually turned the crankshaft pulley. This result indicates that the crankshaft position sensor is not creating a signal.
Before we condemn the sensor as defective, we need to make sure it's getting power and ground. For the next test, go to: TEST 2: Making Sure The Crank Sensor Is Getting Power.