How to Test the Crank Sensor
(GM 4.3L, 5.0L, 5.7L)

CRANK SENSOR TEST 2: Power Circuit

Like any other electrical device, the crankshaft position sensor on your 4.3L, 5.0L and 5.7L equipped GM vehicle needs power to function. This power is in the form of 12 Volts DC that are instantly made available to the crank sensor as soon as you turn the key to the On Position.

This test will help you to confirm that ‘YES, the sensor is getting power’ or ‘NO, it's not getting power’. As in the previous test, you'll be using your multimeter to verify this voltage signal.

These are the test steps:

  1. 1

    Pierce the wire labeled with the letter A in the photo with a wire-piercing probe. Now connect the RED multimeter lead to this wire-piercing probe.

  2. 2

    Connect the BLACK lead of the multimeter to a clean and rust-free ground spot on the frame or engine.

  3. 3

    When everything is set up, turn on you multimeter and place it in Volts DC mode and have your helper turn the Key to the On position. No need to crank the engine for this test.

  4. 4

    Your multimeter should and will register 12 Volts, if everything is OK with this circuit.

Now, let's take a look at what those voltage readings (or lack of) mean:

CASE 1: 12 Volts registered on the multimeter when the ignition was turned On, this multimeter result confirms that the crankshaft position (CKP) sensor is getting power.

The next test is to check that the CKP sensor has a good path to ground. So, go to CKP TEST 3.

CASE 2: 12 Volts DID NOT register when the ignition was turned On,: This result indicates that the ignition module is not supplying power to the crank sensor.

This result exonerates the crankshaft position (CKP) sensor as the cause of the Cranks but Does Not Start Condition you're trying to solve, since without these 12 Volts, the crank sensor can not create a signal.

Power comes from the ECM fuse in the instrument panel fuse box. Check to see if the fuse is blown.

CRANK SENSOR TEST 3: Ground Circuit

The 3-wire crankshaft position sensor has its own independent ground path, and this path to ground is provided by the circuit (wire) labeled with the letter B in the photo in the image viewer.

There are several ways to test for ground in any given circuit, here... you need to be very careful, since the fuel injection computer is the one that provides this ground path internally. Accidentally or intentionally shorting this circuit to power will fry the computer. OK, here's the test:

  1. 1

    Place the multimeter in Volts DC mode and with a wire-piercing probe or an appropriate tool, pierce the wire labeled with the letter B in the image. Connect the BLACK multimeter lead to this tool.

  2. 2

    Connect the RED lead of the multimeter to the battery positive terminal.

  3. 3

    Turn the Key On and your multimeter should register battery voltage (about 12.5 Volts).

Now, let's take a look at what those voltage readings (or lack of) mean:

CASE 1: The multimeter showed 12 Volts when the ignition was turned On, this test result let's you know that the fuel injection computer is providing a good ground path for the crank sensor.

So, taking into account that in CKP TEST 1 you DID NOT get the 5 Volt ON/OFF signal and in CKP TEST 2 your multimeter did register 12 Volts, then you confidently conclude, beyond a shadow of a doubt, that the CKP sensor is BAD. Replacing the CKP sensor will solve the No Start No Spark Condition your vehicle is experiencing.

CASE 2: The multimeter DID NOT show 12 Volts when the ignition was turned On, This result indicates that the fuel injection computer is not supplying a ground path to the crank sensor.

This result exonerates the crankshaft position (CKP) sensor as the cause of the Cranks but Does Not Start Condition you're trying to solve, since without a ground path, the crank sensor can't create a signal.

Its extremely rare for a problem to occur with this circuit, I myself have never seen it. But if this is the result you obtained... the next step is to check that there are no opens in the circuit between the fuel injection computer and the crank sensor.

Chevrolet Vehicles:

  • Astro
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Blazer
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Blazer TrailBlazer
    • 1999, 2000, 2001

Chevrolet Vehicles:

  • C1500, C2500, C3500 Pick Up
    • 1996, 1997, 1998, 1999, 2000
  • Express Van 1500, 2500, 3500
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
  • G30 Van
    • 1996
  • K1500, K2500, K3500 Pick Up
    • 1996, 1997, 1998, 1999, 2000

Chevrolet Vehicles:

  • K1500, K2500 Suburban
    • 1996, 1997, 1998, 1999
  • P30 Van
    • 1996, 1997, 1998, 1999
  • S10 Blazer
    • 1994
  • S10 Pick Up
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004

Chevrolet Vehicles:

  • Silverado 1500 Pick Up
    • 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007
  • Tahoe
    • 1996, 1997, 1998, 1999, 2000

GMC Vehicles:

  • Sierra C1500, C2500, C3500
    • 1996, 1997, 1998, 1999, 2000

GMC Vehicles:

  • Suburban C1500, C2500
    • 1996, 1997, 1998, 1999
  • G3500 Van & Vandura
    • 1996
  • Jimmy & Envoy
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • K1500, K2500, K3500 Sierra
    • 1996, 1997, 1998, 1999, 2000

GMC Vehicles:

  • P3500 Van
    • 1996, 1997, 1998, 1999
  • S15 Jimmy
    • 1994
  • Safari
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005

GMC Vehicles:

  • Savana Van 1500, 2500, 3500
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
  • Sonoma
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004

GMC Vehicles:

  • Yukon
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002

Isuzu Vehicles:

  • Hombre
    • 1997, 1998, 1999, 2000

Oldsmobile Vehicles:

  • Bravada
    • 1996, 1997, 1998, 1999, 2000, 2001

Cadillac Vehicles:

  • Escalade
    • 1999, 2000

“I came from a real tough neighborhood. Why, every time I shut
the window I hurt somebody’s fingers.”

Rodney Dangerfield

MORE TUTORIALS: