How To Test The Cam Sensor 2.4L Nissan Altima (1997-2001)

TEST 2: Checking The 1° POS Signal

If you read the section How Does The Camshaft Position Sensor Work, you know that the camshaft position sensor produces two camshaft position signals.

One camshaft position signal is called the 1° POS Signal and the other is called the 180° REF Signal. Both of these can be very easily and accurately tested with a multimeter in Volts DC mode.

The camshaft position sensor's 1° POS Signal is an ON/OFF voltage signal. To be a bit more specific: ON is when your multimeter registers 5 Volts, OFF is when it registers 0 Volts.

The wire that carries the 1° POS Signal, and the one we're gonna' connect the multimeter to, is the wire labeled with the 3 in the photo above.

NOTE: The distributor must remain connected to its electrical connector for this test to work. To access the 1° POS Signal within the wire, you'll need to use a back probe on the connector or a wire piercing probe on the wire. You can see an example of this tool here: Wire Piercing Probe.

IMPORTANT: To test the 1° POS Signal you'll need to turn the engine by hand. You can accomplish this by turn the crankshaft pulley with a 1/2" ratchet wrench and the appropriate socket. Don't use the starter motor to crank the engine.

This is what you need to do:

1. 1

   Reconnect the distributor to its electrical connector.

2. 2

   Disconnect the fuel injectors from their electrical connectors.
   
   This is an important safety precaution.

3. 3

   Connect the red multimeter test lead to wire labeled with the number 3 using an appropriate tool (like a back probe or a wire piercing probe).
   
   NOTE: The distributor must remain connected to its electrical connector.

4. 4

   Next, connect the black multimeter test lead to the battery negative (-) terminal.

5. 5

   When you have everything set up, turn the engine by hand using the appropriate tools on the crankshaft pulley as you observe your multimeter's display.

6. 6

   Your multimeter should register four ON/OFF voltage pulses per one full turn of the crankshaft.
   
   NOTE: ON is when your multimeter should register 5 Volts and OFF is when it'll register 0 Volts.

Let's examine your test result:

CASE 1: The multimeter registered the ON/OFF voltage pulses. So far so good, since this is the correct and expected test result.

The next step is to check that the camshaft position sensor is producing a good 180° REF Signal, go to: TEST 3: Checking The 180° REF Signal.

CASE 2: The multimeter DID NOT register the ON/OFF pulses. Recheck your multimeter connections and repeat the test.

If the multimeter still does not register the ON/OFF voltage pulses, then the camshaft position sensor is bad and needs to be replaced.

Since the camshaft position sensor is not sold separately, you'll need to replace the whole distributor.

TEST 3: Checking The 180° REF Signal

This test will check/confirm that the camshaft position sensor is producing the 180° REF Signal it needs to start the engine in your 2.4L Nissan Altima.

The camshaft position sensor's 180° REF Signal is also an ON/OFF voltage signal. As mentioned before: ON is when your multimeter registers 5 Volts, OFF is when it registers 0 Volts.

The wire that carries the 180° REF Signal, and the one we're gonna' connect the multimeter to, is the wire labeled with the 4 in the photo above.

NOTE: The distributor must remain connected to its electrical connector for this test to work. To access the 180° REF Signal within the wire, you'll need to use a back probe on the connector or a wire piercing probe on the wire. You can see an example of this tool here: Wire Piercing Probe.

IMPORTANT: To test the 180° REF Signal you'll need to turn the engine very slowly by hand. You can accomplish this by turn the crankshaft pulley with a 1/2" ratchet wrench and the appropriate socket. Don't use the starter motor to crank the engine.

These are the test steps:

1. 1

   Connect the red multimeter test lead to the wire labeled with the number 4 with an appropriate tool (like a back probe or a wire piercing probe).
   
   NOTE: The distributor must remain connected to its electrical connector and the fuel injectors should be disconnected from the previous test.

2. 2

   Next, connect the black multimeter test lead to the battery negative (-) terminal.

3. 3

   When you have everything set up, turn the engine very slowly by hand using the appropriate tools on the crankshaft pulley as you observe the multimeter.

4. 4

   Your multimeter should register ON/OFF voltage pulses as you turn the engine by hand, just like in the previous test (when you were testing the 1° POS Signal in CAM SENSOR 2) except that you'll see a whole more of these pulses.

Let's examine your test results:

CASE 1: The multimeter registered the ON/OFF voltage pulses. This is the correct and expected test result.

The camshaft position sensor is working fine, and not the cause of your Nissan Altima's 'no-spark no-start' problem if you have:

• Confirmed that the camshaft position sensor is receiving 10 to 12 Volts (TEST 1).
• Confirmed that the camshaft position sensor is producing the 1° POS Signal (TEST 2).
• Confirmed that the camshaft position sensor is producing the 180° REF Signal.

CASE 2: The multimeter DID NOT register the ON/OFF voltage pulses. Recheck your multimeter connections and repeat the test.

If the multimeter still does not register the ON/OFF voltage pulses, then the camshaft position sensor is bad and needs to be replaced.

What sucks about this, is that the camshaft position sensor is not sold separately and you'll need to replace the whole distributor.