Buy Nissan Altima Engine Crankshaft Position Sensors

The Nissan Altima's crankshaft position sensor-also called a crank sensor, engine speed sensor, or crank angle sensor-monitors the exact angle and rpm of the crankshaft so the engine computer can fire spark and inject fuel at the right moment. When this small magnetic pickup fails, the Altima may crank but not start, stall at stoplights, or flash a check-engine light.

The crankshaft position sensor sends a high-resolution pulse train to the engine control module (ECM) so it can synchronize ignition timing and sequential fuel injection. Without this steady stream of data, the ECM can't tell where the pistons are, causing loss of spark, mis-timing, or a no-start. A good sensor helps the Altima idle smoothly, maintain fuel economy, and meet emissions rules. Read more in this crankshaft position sensor overview .

• Intermittent stalling-especially when the engine reaches operating temperature (RepairPal.com)
• Long crank or no-start after a hot soak (Endurance Warranty)
• Check-engine light with codes P0335, P0336, P0725, or P0018 (OBD-Codes.com, OBD-Codes.com)
• Poor throttle response and reduced fuel mileage because timing falls back into fail-safe mode (YouTube)
• Rough idle or misfire when the crank signal drops out for fractions of a second (NICOclub Forums)

Nissan's own defect filing shows more than 650,000 Altima sedans built between 2002 and 2006 with the 2.5-liter QR25DE engine can experience crank sensor signal loss that makes the engine shut off without warning. See NHTSA Campaign 07V-527 for full details in the official PDF notice (NHTSA). Driver complaint data confirm that 2003 models top the list for sensor-related stalls and check-engine lights (CarComplaints.com). Later sixth-generation cars (2013-2018) rarely fail, but mileage-induced heat can still degrade the part over time (YouTube).

• P0335/P0336 - "Crankshaft Position Sensor 'A' Circuit" fault (primary failure code).
• P0725 - Engine speed input circuit fault; often cascades from P0335 on Altima ECMs (OBD-Codes.com).
• P0018 - Crank/Cam correlation Bank 2; may appear if timing jumps due to a failing sensor (OBD-Codes.com).

A scan tool will show engine rpm drop to "0 rpm" while cranking if the sensor is dead. Mechanics also back-probe for a five-volt reference, ground, and a clean square-wave signal using an oscilloscope (JustAnswer).

On 2.5-liter engines, the crank sensor sits in the lower rear of the block next to the transmission bell-housing, facing the signal plate teeth on the crankshaft. V6 Altimas place it near the right-side oil pan flange. Access is from under the car; feel behind the engine for the 10 mm bolt securing the sensor body (, x.nissanhelp.com).

DIY videos show the service takes 15 - 30 minutes with a 10 mm socket, extension, and ratchet: disconnect the battery, unplug the harness, remove one bolt, twist the sensor free, oil the new O-ring, insert straight, and retighten to 62 in-lb. Always clear the codes and perform an idle relearn after installation (YouTube, YouTube). Many techs recommend replacing the companion camshaft position sensor at the same time because they share wiring and age together (x.nissanhelp.com).

• Keep oil leaks off the sensor-oil can wick into the connector and short the Hall-effect circuitry.
• Use dielectric grease on the three-pin plug to block moisture intrusion common on Altimas from humid climates (NICOclub Forums).
• Inspect engine mounts; excessive vibration speeds sensor fatigue.
• If you live where road salt is heavy, rinse the under-engine area to minimize corrosion around the lower bell-housing.

Nissan's recall bulletin warns that a sudden loss of crank signal can shut the engine off at low speeds, increasing crash risk. Dealers reprogrammed the ECM to ignore micro-dropouts until the driver can restart, but owners can still request a one-time free sensor swap if VINs fall under the campaign window. Full bulletin text is linked here: NHTSA Recall 07V-527 PDF . Independent warranty studies echo the concern, noting failures as early as 60,000 miles (Endurance Warranty).

• Fits Altima 2.5 L QR25DE (2002-present) and 3.5 L VQ35DE (2002-2008).
• Signal type: three-wire Hall-effect.
• Reference voltage: 5 V; output toggles 0-5 V square wave.
• Air gap (tip to reluctor): 0.02 - 0.04 in.
• Torque spec: 7 N·m (62 in-lb) sensor bolt (NHTSA).

Q: What's the fastest way to confirm the sensor is bad?
A: Plug in an OBD-II reader. If rpm reads 0 while cranking and code P0335 is pending, the crank sensor is not sending a signal. Voltage and ground checks with a multimeter can double-confirm. (OBD-Codes.com)

Q: Is it safe to drive with a weak crank sensor?
A: No. A weak signal may let the engine run but can stall suddenly, even in traffic, as noted in Nissan's safety filing. (NHTSA)

Q: Do I have to reprogram anything after replacement?
A: Most Altima ECMs learn automatically, but clearing codes and performing an idle relearn (turn key "ON" for three seconds, etc.) prevents rough idle. (YouTube)

Q: Why do cam and crank sensors fail together?
A: Both sit low on the block and face similar heat, oil vapor, and vibration; replacing them in pairs avoids repeat repairs. (x.nissanhelp.com)

Q: What tools are required?
A: Jack stands, 10 mm socket, 3-inch extension, ratchet, and a small pick to release the connector tab. (YouTube)

Q: Which DTCs besides P0335 point to crank sensor trouble?
A: P0336 (range/performance), P0725 (engine speed input), and sometimes P0018 (crank/cam correlation). (OBD-Codes.com, OBD-Codes.com)

Q: Will a bad crank sensor damage other parts?
A: It can load the catalytic converter with unburned fuel after misfires and may overheat the starter from multiple crank attempts. (YouTube)

Q: How much does professional replacement cost?
A: Average shop quotes run US $180-$250 including labor, according to aggregated repair data. (RepairPal.com)

Q: Are aftermarket sensors reliable?
A: Yes-as long as the part meets OE spec and has the correct Hall-effect circuitry; avoid bargain units lacking heat-resistant epoxy. (NICOclub Forums)

Q: Can a scan tool reset the sensor?
A: No. The sensor is a passive device; faults clear only after a working unit is installed and codes are erased. (x.nissanhelp.com)

Nissan Altima crankshaft position sensors.