engine

Knock Sensor

for 1994–2007 Dodge Ram 2500 5.9L I6 Cummins Diesel · 4WD

Difficulty

Moderate

Time

1.7 h

Tools

Steps

🔍Draft — verification in progress. This procedure was built from OLP's spec database on August 20, 2026 and is queued for line-by-line review by Chris Hackleman — master technicians with 20+ years each. That review typically completes within 3 days of generation, and this banner changes to a verified badge the moment it does. Until then, cross-check every torque value and fluid capacity against the factory manual, and stop if anything looks unsafe. If something looks off, report it below — a real person reads every report.

This procedure covers the removal and replacement of the knock sensor on the 5.9L Cummins diesel engine, which is located on the driver's side of the engine block.

Warnings

⚠Allow engine to cool completely before starting work. The knock sensor area retains heat and can cause burns.

⚠The knock sensor is torque-critical for proper operation. Under-torquing or over-torquing will cause false readings and potential engine damage.

ℹ️Do not use thread sealant on the knock sensor threads. Use only anti-seize if specified by the replacement sensor manufacturer.

Tools required

Socket set with 1/4" and 3/8" driveEssential

Torque wrench (5-50 lb-ft range)Essential

Ratcheting wrench set

Pick set or small flathead screwdriver

Wire brush

Shop towelsEssential

Battery terminal wrenchEssential

Anti-seize compound

Electrical contact cleaner

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Parts

Knock sensor × 1 — Mopar 4921517 or equivalent
Anti-seize compound × 1 — Use OEM specification

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Preparation

Park vehicle on level ground and allow engine to cool completely (minimum 2 hours)
Disconnect negative battery cable to prevent electrical shorts
If equipped with an engine cover, remove cover bolts and set aside
Gather all tools and parts before beginning

Procedure

1
Locate the knock sensor
The knock sensor is located on the driver's side of the engine block, approximately mid-way down the block between cylinders 3 and 4. It will have a single wire connector attached. Access is typically from above, though you may need to work around fuel lines and wiring harnesses.
2
Disconnect the knock sensor electrical connector
Locate the electrical connector on the knock sensor. Press the locking tab and carefully pull the connector straight off the sensor. If the connector is stuck due to corrosion, use a small flathead screwdriver or pick to gently pry around the edges while pulling. Do not damage the connector or wiring.
3
Clean the area around the knock sensor
Use a wire brush and shop towels to clean any dirt, oil, or debris from around the knock sensor mounting area. This prevents contamination from falling into the sensor bore when the sensor is removed. Pay special attention to the area immediately around the sensor threads.
4
Remove the old knock sensor
Using an appropriate socket (typically 22mm or 7/8"), carefully remove the knock sensor by turning counterclockwise. If the sensor is seized, do not force it. Apply penetrating oil and allow it to soak for 15-30 minutes before attempting removal again. Remove the sensor completely from the engine block.
5
Inspect the sensor bore and threads
Examine the threaded hole in the engine block for any damage, debris, or old sealant. Use a wire brush to clean the threads if necessary. Check that the threads are not stripped or cross-threaded. Wipe the area clean with a shop towel. The mounting surface must be clean and free of debris for proper sensor function.
6
Prepare the new knock sensor
Inspect the new knock sensor for any shipping damage. Check that the threads are clean and undamaged. If recommended by the sensor manufacturer, apply a small amount of anti-seize compound to the threads only (not to the sensor tip or mounting surface). Do not use thread sealant or excessive anti-seize as this can affect sensor readings.
7
Install the new knock sensor
Thread the new knock sensor into the engine block by hand, ensuring it threads in smoothly without resistance. Turn clockwise until the sensor is hand-tight and seated against the engine block. Do not cross-thread the sensor.
Torque spec
Knock Sensor20 Nm (15 lb-ft)
8
Torque the knock sensor to specification
Using a calibrated torque wrench, tighten the knock sensor to exactly 20 Nm (15 lb-ft). This torque specification is critical for proper sensor operation. The sensor must make solid mechanical contact with the engine block to accurately detect vibrations. Over-torquing can damage the sensor, while under-torquing will cause false readings.
Torque spec
Knock Sensor20 Nm (15 lb-ft)
9
Reconnect the electrical connector
Clean the electrical connector terminals with electrical contact cleaner if available. Push the electrical connector firmly onto the knock sensor until you hear or feel it click into place. Ensure the locking tab is fully engaged. Gently tug on the connector to verify it is secure.
10
Reinstall any removed components
If an engine cover was removed, reinstall it and tighten the cover bolts to specification. Ensure all wiring harnesses and fuel lines are properly routed and secured. Reconnect the negative battery cable.

Reassembly

Double-check that the knock sensor electrical connector is fully seated and locked
Verify all wiring and hoses are properly routed away from hot exhaust components
Confirm the torque wrench was set to the correct specification (20 Nm / 15 lb-ft) for the knock sensor

Verification

Start the engine and verify it runs smoothly without any new warning lights
Use a scan tool to check for any knock sensor related diagnostic trouble codes (DTCs)
Allow the engine to reach operating temperature and verify no check engine light appears
If equipped with a scan tool capable of live data, verify the knock sensor is providing readings (typically should show 0-5 volts at idle)
Test drive the vehicle under light acceleration and verify no abnormal engine operation or check engine light