Volvo Penta Crankshaft Position Sensor 3858979

Volvo Penta OEM Crankshaft Position Sensor Part No. 3858979

Compatible Applications

Volvo Penta used several different sensors in the same engine-control system including separate MAP, throttle-position, camshaft-position, knock, and crankshaft-position sensors. Confirm the exact engine model, serial number, and electronic engine-control diagram before ordering. Do not substitute by appearance alone.

• Volvo Penta 4.3GL-A / B / C / D / E / G
• Volvo Penta 4.3GXi-B and related GXi variants
• Volvo Penta 4.3OSi
• Volvo Penta 5.0GXi / 5.0OSi (including 5.0GXi-D)
• Volvo Penta 5.7Gi / 5.7GXi (including 5.7Gi-300)
• Volvo Penta 5.7OSi / 5.7OSXi

Symptoms of a Failing Crankshaft Position Sensor

Electronic diagnosis is recommended before replacing the sensor several ignition and fuel-control faults can produce similar symptoms. Common indicators include:

• Intermittent or complete no-start condition
• Engine stalling without warning
• Erratic ignition timing
• Loss of engine-speed signal at the ECM
• Intermittent misfire under load
• Crank-position related fault codes stored in the ECM
• Physical damage to the sensor body or connector

Installation Notes

The sensor installs at the timing-cover area and interfaces directly with the ECM. Before installation, inspect the electrical connector, wiring harness, sensor mounting surface, and the related O-ring (3859009), which appears adjacent to 3858979 in several Volvo Penta engine-control diagrams. Avoid contacting the sensor tip against hard surfaces during handling, and follow the Volvo Penta service procedure for the exact engine model.

Technical FAQ

Is this the same as a MAP sensor or camshaft position sensor?
No. The MAP sensor (3858987) and camshaft position sensor (3863130) are separate parts that appear in the same engine-control system. Some listings incorrectly identify 3858979 as a MAP sensor multiple marine ignition catalogs and Volvo Penta engine-control diagrams consistently identify it as the crankshaft position sensor.

Can I diagnose this sensor myself?
With the right diagnostic scanner and Volvo Penta wiring information, crank-position sensor faults can often be isolated. However, because no-start and stalling conditions can have multiple causes, professional electronic diagnosis is recommended before replacing the sensor.

Does this fit both GL and GXi versions of the 4.3L?
Yes confirmed applications include both 4.3GL (A through G suffix) and 4.3GXi variants. Different sensors may be used in other engine-control positions on the same engine. Confirm by full model designation and serial number.

Are the aftermarket cross-references (Sierra, CDI, Mallory) direct equivalents?
They are listed as cross-references for this application in aftermarket catalogs. Verify the cross-reference against your exact engine model and serial number before use, as aftermarket sensor specifications can vary.

Parts Desk Insights

The most common issue with this part is being confused with the MAP sensor (3858987) or camshaft sensor (3863130) all three are in the same Volvo Penta engine-control system and can look similar. Customers usually arrive at this sensor after a no-start or stalling diagnostic, and confirming the fault code or sensor function before ordering saves the most time. At $322, its worth doing proper diagnosis first rather than replacing sensors by elimination.