What This Sensor Does
This is a thermistor-style fluid temperature sensor. Resistance changes with temperature, the ECM reads that change as a voltage on a two-wire circuit, and it uses the value for fan control, fuel timing, cold-start strategy and protective derates. Depending on the port it is installed in, the same sensor reads oil, coolant or fuel temperature. The engine does not know the difference — the harness and the ECM calibration do.
Failure is usually electrical, not mechanical. The sensing element drifts, or the epoxy seal at the connector cracks and lets coolant or oil wick into the pins. You get a reading that is stuck high, stuck low, or jumps around at idle. A stuck-low reading keeps the fan off and the timing wrong. A stuck-high reading pulls power for no reason.
The body threads into an M14 x 1.5 port and uses a sealed two-pin connector. Housing and connector are built to live in engine-bay heat and vibration. No adapters, no port machining — it goes into the factory boss the old sensor came out of.
Why These Numbers Cross
Cummins carried this temperature sensor under several numbers as the ISX family moved through revisions. 4954905, 3096153, 4088750 and 4088751 all describe the same sensing function in the same M14 x 1.5 thread with the same two-pin sealed connector. The changes behind those numbers were supersessions, connector keying updates and packaging revisions rather than a different sensor design.
PAI 050672 is an aftermarket line number covering the same Cummins application. Aftermarket suppliers assign their own numbering, so a single Cummins part often shows up under one PAI number and several Cummins numbers at the same time. That is why a parts screen can return five results for one physical sensor.
We list all of those numbers for identification only. If the number stamped on your old sensor is on that list, 3865346 is the correct starting point. It is a starting point — not a fitment promise. Confirm against the number on the removed part or against your engine serial number before you order.
Check Before You Order
Pull the old sensor and read the number on the body. That number, plus your engine serial, is what settles the question. ISX, ISX15 and QSX15 engines carry temperature sensors in more than one location, and the ports are not always identical across build dates. Note which port the sensor came from and match the thread before installing.
Before you condemn the sensor, check the harness. Back-probe both pins and look for corrosion, green pins, or a chafed lead rubbing a bracket. Wiggle-test the connector with the engine running and watch the live data. A reading that jumps when you move the harness is a wiring problem — a new sensor will not fix it.
3865346 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 3865346. 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 | 4954905, 3096153, 4088750, 4088751 |
| PAI | 050672 |
Frequently asked questions
Is 3865346 an oil sensor or a coolant sensor?
Both. It is the same sensing element used for oil, coolant and fuel temperature depending on which port it is installed in. The ECM assigns the reading based on the circuit it is wired into. Match the port your old sensor came out of.
Will this fit my ISX if the old sensor says 4088750?
4088750 is one of the numbers that crosses to 3865346, so it is the right place to start. Cross-reference is not a fitment guarantee. Verify against your engine serial number and confirm the M14 x 1.5 thread on the port before installing.
Do I need to program the ECM after replacing this sensor?
No. It is a passive thermistor with no onboard electronics, so there is nothing to calibrate. Clear the stored fault code after installation and verify the live temperature reading tracks correctly during warm-up before returning the truck to service.
Not sure it fits? We check before you pay.
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.
More cross-reference guides
Need the part, not just the reading?
Every part below is a Premium Quality aftermarket Direct Replacement with published OEM cross-reference numbers, a 6+ month warranty and same-business-day shipping from Tacoma, WA. Not sure it fits? Run your VIN — or call and a person who knows trucks will verify fitment before you pay.