What This Sensor Does
This is a three-pin magnetic pickup that reads a toothed target on the crankshaft and reports position and speed to the ECM. The ECM uses that signal to set injection timing and to decide when to fire. Lose the signal and the engine either cranks without starting or runs off the backup camshaft signal with rough timing and reduced power.
On the ISX15, QSX15 and X15 family the same sensor part serves both crankshaft and camshaft locations. That is convenient for stocking, but it means you have to confirm which position you are replacing before you pull anything. Note the harness routing and connector orientation while the old sensor is still in the bore.
Typical failure is heat and vibration related. The winding opens or the signal drifts, and you get an intermittent drop-out that shows up hot, on rough road, or at idle. Codes for engine speed or position signal loss, hard hot starts, and stalls that clear after a key cycle all point here. Check the connector pins and harness chafe before condemning the sensor.
Why These Numbers Cross
4921686, 4921687, 5594276 and 3408531NX all describe the same magnetic position/speed pickup used across the Cummins ISX15, QSX15 and X15 platform. The numbers differ because of supersessions and build-out changes over the production run, not because the sensing element changed. Same pin count, same signal output, same mounting bore.
3408531NX is a new-exchange designation. It refers to a unit supplied under Cummins' exchange program rather than a different design, so it appears in interchange lists alongside the straight service numbers. If that is the number stamped on your old sensor or listed on your work order, this is the correct part family to be looking at.
These numbers are listed for identification only. PartStop is an independent aftermarket supplier and is not affiliated with, endorsed by, or authorized by Cummins. A cross-reference is a starting point — confirm fit against your engine serial number or the number printed on the sensor you are replacing.
Before You Order
Pull the old sensor and read the number off the body. That beats guessing from a parts catalog, especially on a truck that has already had a sensor swapped once. If the label is unreadable, get your engine serial number off the dataplate or the block pad and verify against that.
Check the connector before you order. Confirm the three-pin plug matches, and inspect the harness pigtail for green pins, spread terminals, or chafed insulation. A corroded connector will make a new sensor look defective. This part is a direct replacement for the listed numbers, but fitment is confirmed by VIN or by the old part number, not by the cross-reference alone.
4921686 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 4921686. Use them to identify the part — then confirm the exact fit by VIN or the number stamped on your old unit before you order. An interchange is a starting point, not a fitment guarantee.
| Brand / Line | Cross-Reference Numbers |
|---|---|
| Cummins | 4921687, 5594276 |
| Cummins (New-Exchange) | 3408531NX |
Frequently asked questions
Is 4921686 the crank sensor or the cam sensor?
On this Cummins family the same sensor is used in both the crankshaft and camshaft positions. The part number does not tell you which one you are holding. Note the mounting location and harness routing before you remove the old unit so you put the new one back in the right bore.
Will 5594276 or 4921687 work in place of 4921686?
Those numbers appear in the interchange for this sensor and describe the same three-pin magnetic pickup. They exist because of supersessions over the production run. Still verify against the number on your old sensor or your engine serial number — an interchange list is a starting point, not a fitment guarantee.
My truck cranks but won't start. Is this the sensor?
It's a common cause, but check the connector and harness first. Corroded pins, a chafed wire, or a loose plug will produce the same no-start and the same fault codes as a failed sensor. If the wiring is clean and the code points at engine position or speed signal loss, the sensor is the likely culprit.
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Run your VIN and we’ll match parts to your exact truck, or call the counter — a person who knows trucks verifies fitment by OEM number before the order ships. No wrong-box returns.
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