How to Put a Crank Sensor in a 2003 Altima

The crankshaft position sensor on the 2003 Altima is a magnetic sensor that uses the teeth on the end of the crankshaft to detect the fluctuation of engine revolutions. When this sensor fails, the engine control module no longer knows the speed at which the engine is running and defaults to open loop or its default settings. Replacing a failed sensor in the Altima is a simple task on the 3.5-liter engine. The 2.5-liter engine is a different animal altogether. The process itself is the same for the two engines, but the positioning and ease of access differs greatly between the two.

Instructions

1

Raise the front of the Altima with a floor jack and slide jack stands under the vehicles subframe. Lower the Nissan onto the jack stands.

2

Crawl beneath the vehicle and find the crankshaft position sensor. On Altimas with the 3.5-liter engine, Nissan positioned the sensor near the front of the vehicle, mounted on the end of the oil pan closest to the transmission, near the top of the pan. On the 2.5-liter, it is harder to see, as Nissan mounted it toward the rear of the engine just below the starter.

3

Remove the bolt securing the sensor, using a ratchet and socket. Pull the sensor outward with a slight twisting motion. On the 2.5-liter engine, use needle-nose pliers to gain a firm grip on the sensor, as it is a tight fit if you have larger hands and arms.

4

Push the green tab on the wiring harness away from the sensor with a flat-head screwdriver until you hear it click. Unplug the harness from the sensor.

5

Set the new rubber seal on the opposite side of the bolt hole on the new sensor for the 3.5-liter engine.

6

Apply a thin coat of new engine oil onto the O-ring, using your fingers.

7

Plug the wiring harness into the new sensor and slide the green tab toward the sensor until you hear it click to lock it into place. Pull on the harness to check that it is locked onto the sensor. If the harness pulls off easily, slide the green tab away from the sensor, unplug the sensor and repeat this step.

8

Guide the sensor into its hole in the engine. Hand-thread the sensors retaining bolt, then toque it to 8 foot-pounds on the 3.5-liter engine or 5 foot-pounds on a 2.5-liter, using a torque wrench and socket.

9

Raise the Altima off the jack stands with a floor jack and remove the jack stands. Lower the vehicle to the ground.