Chrysler Pacifica Vehicle Speed Sensor Guide (2004-2008)
Solve erratic shifting and speedometer problems in your 2004-2008 Chrysler Pacifica.
- Your Pacifica has two transmission speed sensors (input and output); it's best to replace them in pairs.
- Common symptoms are erratic shifting and a faulty speedometer, often with engine code P0720.
- Before replacing sensors, have your alternator checked, as a bad one can cause identical symptoms.
- This is an easy DIY repair that can be completed in about an hour with basic tools.
Is Your Pacifica Shifting Hard or is the Speedometer Acting Up?
If you're experiencing strange transmission behavior with your 2004-2008 Chrysler Pacifica, a faulty vehicle speed sensor is a common and inexpensive culprit. Before assuming you have a major transmission failure, which can be a known issue on these vehicles, it's crucial to check these sensors. A bad sensor can mimic the symptoms of a failing transmission but is much easier and cheaper to fix.
Symptoms of a Failing Pacifica Speed Sensor
When a speed sensor starts to fail, your Pacifica's computer receives incorrect or no data about how fast you're moving. This can cause a number of problems:
- Erratic or Harsh Shifting: The transmission may slam into gear, hesitate between shifts, or get stuck in one gear (known as "limp mode").
- Inaccurate Speedometer: The speedometer needle may jump around, read 0 mph while driving, or even show a speed when you're stopped. 🎬 Watch: See how an erratic speedometer behaves when a sensor fails.
- Check Engine Light: A failing sensor will almost always trigger a Check Engine Light. You'll likely see trouble code P0720 (Output Speed Sensor Circuit Malfunction) along with the general transmission code P0700.
- Cruise Control Failure: The cruise control system relies on speed data, so it will stop working if the sensor is bad.
A Hidden Cause: The Alternator
A well-documented issue on Chrysler vehicles of this era is interference from a failing alternator. A bad diode in the alternator can create electrical "noise" (AC ripple) that disrupts the speed sensor's signal, causing the exact same symptoms as a failed sensor, including a P0720 code. Before replacing the sensors, it's wise to have your alternator tested to ensure it's not the real source of the problem.
🎬 Watch: Troubleshooting P0720 codes and alternator issues.Choosing the Right Aftermarket Speed Sensor
For a part like this, you don't necessarily need to pay top dollar for an OEM Mopar part. High-quality aftermarket brands offer reliable performance at a much lower cost. The main risk of a cheap, low-quality sensor is premature failure, forcing you to do the job twice. Here’s a breakdown of available brands:
- Tier 1 (High-Quality Aftermarket): Brands like Delphi and Standard Ignition (SMP) are known for producing parts that meet or exceed original equipment specifications. They are trusted choices for reliability and are often used by professional mechanics.
- Tier 2 (Standard Aftermarket): Brands like Walker Products, Holstein, and Crown Automotive offer a good balance of quality and value. They are generally reliable for common repairs.
- Tier 3 (Economy): Brands such as URO Parts, Skyward, and True Tech are budget-friendly options. While URO Parts is known for its wide range, especially for European cars, user feedback suggests quality can be inconsistent for electronic parts. These may be suitable if budget is the primary concern, but failure rates can be higher.
Pro Tip: Replace in Pairs
Your Pacifica has both an input and an output speed sensor. They are identical in age and have experienced the same conditions. It is highly recommended to replace both sensors at the same time. Many are sold as a set for this reason. This prevents you from having to do the same repair a few months later when the second original sensor fails.
Cost of Replacing a Chrysler Pacifica Speed Sensor
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket Sensor (Single) | $13.98 - $42.57 |
| New OEM Mopar Sensor (Single) | $50 - $75 |
| Shop Labor | $85 - $135 |
Frequently Asked Questions
How many speed sensors does my 2004-2008 Pacifica have?
Your Pacifica's automatic transmission uses two primary speed sensors: an Input Speed Sensor (ISS) and an Output Speed Sensor (OSS). The OSS is what provides the signal for your speedometer. Both are critical for controlling transmission shifts, and it's best practice to replace them as a pair.
Where are the speed sensors located?
The sensors are mounted externally on the transmission case. The input sensor is generally accessible from the top of the engine bay. The output sensor is located on the side of the transmission, and is most easily accessed by removing the driver's side front wheel.
Can I drive my Pacifica with a bad speed sensor?
You can, but it's not recommended for long. Your transmission may shift harshly or unpredictably, and your speedometer will be unreliable. The vehicle may enter a "limp mode," where it gets stuck in one gear (usually 2nd) to protect the transmission, limiting your speed. It is best to get it repaired as soon as possible.
Is this a difficult DIY repair?
No, this is a great DIY job for a beginner. The sensors are held in by a single bolt and have a simple electrical connector. The most difficult part is safely jacking up the vehicle and removing the wheel for the output sensor. The entire job for both sensors can typically be done in under an hour.
🎬 See this walkthrough for replacing both input and output sensors.What do the codes P0700 and P0720 mean?
P0700 is a generic code that simply means the Transmission Control Module (TCM) has detected a fault and has turned on the Check Engine Light. You need a more advanced scanner to read the specific transmission code, which is often P0720. P0720 points directly to a problem with the Output Speed Sensor circuit, confirming the sensor or its wiring is the likely issue.
Helpful Videos
Technical Specifications
OEM Part Numbers: 4800878 4800879 04800878 04800879
The 2004-2008 Chrysler Pacifica uses two interchangeable sensors for the transmission input and output speed readings. They are magnetic sensors held in by a single bolt with a 2-pin electrical connector.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Chrysler Pacifica:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Is Your Pacifica Shifting Hard or is the Speedometer Acting Up?
- Symptoms of a Failing Pacifica Speed Sensor
- A Hidden Cause: The Alternator
- Choosing the Right Aftermarket Speed Sensor
- Pro Tip: Replace in Pairs
- Cost of Replacing a Chrysler Pacifica Speed Sensor
- Frequently Asked Questions
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