What the crank sensor does and why it fails on the 1999 Viper

The crankshaft position sensor on your 1999 Viper tells the engine computer where the crankshaft is in its rotation at any given moment. The computer uses this signal to time the fuel injectors and ignition spark. When the sensor fails, the engine will not start, will stall randomly while running, or will run so rough you cannot drive it safely.

The 1999 Viper's crank sensor sits inside the engine block near the crankshaft, where it experiences heat, vibration, and oil exposure. After 20+ years, the sensor's internal wiring degrades and the connector corrodes. You will see a check engine light with code P0335 (crankshaft position sensor malfunction) or P0336 (crankshaft position sensor range/performance). Some owners report the sensor failing without warning; others notice the problem building over weeks as the signal becomes intermittent.

Key Takeaways

  • The crank sensor on a 1999 Viper is located on the driver side of the engine block, below the intake manifold, and requires removing the intake manifold to reach it.
  • Replacement takes 2 to 4 hours for someone with basic mechanical skill; the sensor itself costs $40 to $80, but labor at a shop typically runs $300 to $500.
  • You will need a socket set, screwdrivers, a gasket scraper, new intake manifold gaskets, and a torque wrench calibrated to 25 foot-pounds for the sensor bolt.
  • The sensor connector is prone to corrosion; cleaning the pins with electrical contact cleaner before installation prevents premature failure of the new part.
  • A faulty crank sensor can trigger limp mode or prevent starting entirely, but a code reader will confirm the diagnosis before you begin work.

Locating the sensor and what you need to remove to reach it

The crank sensor on the 1999 Viper is bolted to the driver side of the engine block, directly below the intake manifold. To access it, you must remove the intake manifold, which means disconnecting the fuel rail, vacuum hoses, coolant hoses, and electrical connectors. This is not a hidden-location job—it is a full intake removal.

Start by disconnecting the negative battery terminal. Remove the air intake tube and the fuel cap to relieve fuel system pressure. Unbolt the fuel rail from the intake manifold (there are typically four bolts), then carefully pull the rail away from the injectors without yanking the fuel lines. Disconnect all vacuum hoses from the manifold and label them with tape so you can reconnect them in the correct order. Unbolt the intake manifold itself—there are usually six to eight bolts around the perimeter. Once the manifold is clear, you will see the crank sensor mounted on a bracket on the block.

Removing the old sensor and installing the new one

The crank sensor is held in place by a single bolt. Unplug the electrical connector—it may be stuck from corrosion, so wiggle it gently side to side rather than pulling straight. Use a socket wrench to remove the bolt, then slide the sensor out of its bracket. Inspect the connector pins for white or green corrosion. If you see it, clean the pins on both the sensor connector and the wiring harness with electrical contact cleaner and a small brush before you install the new sensor.

Insert the new sensor into the bracket and hand-tighten the bolt first. Use a torque wrench to tighten it to 25 foot-pounds—do not over-tighten, as the bolt can strip the aluminum block. Plug in the connector, making sure it seats fully and clicks into place. Reconnect the intake manifold using new gaskets (reusing old gaskets often causes vacuum leaks). Torque the manifold bolts in a crisscross pattern to 25 foot-pounds as well.

Reassembling the intake system and testing

Reconnect the fuel rail to the injectors, then bolt it back to the manifold. Reattach all vacuum hoses in the order you labeled them. Reconnect coolant hoses and electrical connectors. Reinstall the air intake tube. Double-check that every bolt is tight and every connector is seated before you start the engine.

Turn the key to the on position (do not start) and listen for the fuel pump to prime for a few seconds. Start the engine and let it idle for 30 seconds. The check engine light should go out within a few seconds if the sensor is working. If the light stays on, turn off the engine, wait 10 seconds, and restart. If the light persists, use a code reader to check for new fault codes. A successful replacement will show no crank sensor codes and smooth idle with no hesitation during acceleration.

Tools and parts you will need

You will need a socket set (10mm, 13mm, and 15mm sockets are typical for the 1999 Viper), screwdrivers (Phillips and flat-head), a gasket scraper or plastic putty knife, a torque wrench, and electrical contact cleaner. Buy a new crank sensor (OEM Dodge part number 4874371 or equivalent aftermarket sensor), new intake manifold gaskets, and new fuel injector O-rings if you plan to remove the fuel rail. A jack and jack stands are essential if you need to lift the vehicle for clearance, though many owners work from above without lifting.

The sensor itself runs $40 to $80 depending on whether you buy OEM or aftermarket. Intake manifold gasket sets are $15 to $30. If you take the vehicle to a shop, expect labor charges of $300 to $500 on top of parts, since the intake removal is time-consuming. Doing the work yourself saves the labor cost but requires patience and attention to detail during reassembly.

Common mistakes and how to avoid them

The most frequent error is forgetting to label vacuum hoses before disconnecting them. The 1999 Viper has multiple vacuum lines, and reconnecting them incorrectly will cause rough idle, hesitation, or stalling. Take a photo of the engine bay before you start, or use masking tape and a marker to label every hose at both ends.

A second mistake is over-tightening the crank sensor bolt. The bolt threads into aluminum, and excessive torque will strip the hole, forcing you to drill it out and use a larger bolt or threaded insert. Tighten to 25 foot-pounds and stop. Similarly, over-tightening intake manifold bolts can warp the manifold and cause vacuum leaks. Use a torque wrench for both jobs.

Corrosion in the sensor connector is often overlooked. If you install a new sensor into a corroded connector, the new sensor will fail within months. Clean both sides of the connection with electrical contact cleaner before plugging in the new sensor. If the connector is severely corroded, consider replacing it as well.

When to replace the sensor versus cleaning the connector

If your check engine light shows code P0335 or P0336, the sensor itself is likely faulty and needs replacement. However, if the code is intermittent and the engine runs fine most of the time, a corroded connector may be the culprit. You can test this by unplugging the sensor connector, cleaning both sides with electrical contact cleaner, and plugging it back in. Clear the code with a code reader and drive the vehicle for a few days. If the code does not return, the connector was the problem and the sensor is still good.

If the code returns when ready after cleaning, the sensor is failing and must be replaced. Replacing the sensor is the permanent fix; cleaning the connector is a temporary measure that may buy you time if you cannot do the work when ready.

Frequently Asked Questions

Can I replace the crank sensor without removing the intake manifold?

No. On the 1999 Viper, the sensor is positioned directly under the intake manifold, and there is no way to access it without removing the manifold first. Some vehicles have the sensor in an easier location, but this one does not.

What is the difference between the crankshaft sensor and the camshaft sensor?

The crankshaft sensor monitors the crankshaft rotation and is essential for starting and running the engine. The camshaft sensor monitors the camshaft and helps the computer time the fuel injectors precisely. Both can fail independently. If your check engine code is P0335 or P0336, it is the crankshaft sensor. If it is P0340 or P0341, it is the camshaft sensor.

How long does a new crank sensor last?

A quality replacement sensor typically lasts 80,000 to 150,000 miles or 10 to 15 years. The 1999 Viper is now over 20 years old, so any original sensor is well past its expected life. Aftermarket sensors are usually as reliable as OEM parts if you buy from a reputable supplier.

Will a bad crank sensor cause the check engine light to come on when ready?

Not always. A sensor that is failing gradually may trigger the light intermittently at first, then constantly as it degrades further. Some owners notice the light flashing during acceleration before it stays on. If the sensor fails completely, the engine will not start at all.

Do I need to clear the check engine code after replacing the sensor?

The code will usually clear itself after you start the engine and it runs for a few minutes without detecting a fault. If the light stays on after 10 minutes of driving, use a code reader to clear it manually. If the code returns, the new sensor is defective or the connector is still corroded.