Jeep Cherokee 1991-2001 Automatic Transmission Output Speed Sensor Guide
Solve erratic shifting and Check Engine Light code P0720 on your XJ Cherokee.
- A bad output speed sensor causes shifting problems (P0720 code), not speedometer issues.
- Replacement on 4WD models is difficult due to a blocking bracket, making professional installation common.
- Choose a quality aftermarket brand like NGK (NTK) or Standard Ignition, as Jeeps can be sensitive to out-of-spec sensors.
- Symptoms include harsh shifting, getting stuck in gear, and a Check Engine Light.
Is Your Cherokee Shifting Strangely?
If you're dealing with a Check Engine Light and your AW4 automatic transmission is acting up, a faulty output speed sensor is a likely culprit. This sensor's failure is a well-known issue on the 1991-2001 Jeep Cherokee XJ. When it fails, it typically triggers Diagnostic Trouble Code (DTC) P0720, which points to a malfunction in the output speed sensor circuit. This guide will walk you through the symptoms, how to choose the right replacement part, and what the replacement job entails.
🎬 Watch this walkthrough of the speed sensor replacement process.Symptoms of a Failing Output Speed Sensor
A bad output speed sensor makes itself known through the transmission's behavior. You will likely experience one or more of the following issues:
- Harsh or Delayed Shifting: The transmission may slam into gear or hesitate long before shifting.
- Stuck in Low Gear: The transmission may go into a "limp mode" and refuse to shift out of first or second gear to protect itself.
- Erratic Shifting: You might notice the transmission hunting for gears, or shifting up and down unexpectedly.
- Check Engine Light: A P0720 code is the most common indicator. You may also see a general transmission fault code, P0700.
- No Reverse on Cold Starts: Some owners report a loss of the reverse gear until the vehicle warms up.
Don't Confuse the Two Speed Sensors!
Your XJ has two very similar sensors that are often mixed up. The Transmission Output Speed Sensor (OSS) is located on the transmission itself and controls shifting (related to code P0720). The Vehicle Speed Sensor (VSS) is on the transfer case output housing and controls the speedometer. This article is about the transmission OSS for shifting problems.
Choosing the Right Aftermarket Sensor
When it comes to sensors for Jeeps, quality matters. The vehicle's computer is sensitive and expects signals to be within a specific range. While an OEM Mopar sensor is always an option, high-quality aftermarket parts can offer a reliable repair for less money. Based on owner experiences, aftermarket brands fall into tiers.
Tier 1: OEM Equivalents
NGK (also NTK): This brand is widely trusted in the Jeep community and is the original manufacturer for many of Chrysler's sensors. For critical electronic parts, NGK is often considered the best aftermarket choice for reliability that rivals the original Mopar part.
Tier 2: Reputable Aftermarket
Standard Ignition (Standard Motor Products): SMP is a long-standing aftermarket manufacturer. Their parts are generally considered a solid, budget-friendly alternative to OEM. While they may not have the same OEM-supplier reputation as NGK for Jeep parts, many owners use them without issue.
Tier 3: Economy/Unknown
True Tech: There is very little information available in forums and reviews regarding the quality of "True Tech" brand sensors. This lack of feedback makes it a riskier choice compared to more established brands like NGK or Standard Ignition. For a critical sensor like the OSS, it's generally safer to stick with a brand known for its electronic components.
Pro Tip: For the 1998-2001 AW4 transmission, the input and output speed sensors are the same part number. If you're unsure which is bad or want to be thorough, you could consider replacing both at the same time.
Replacement Cost
The cost to replace the output speed sensor can vary. The part itself is affordable, but labor can be high due to difficult access on 4WD models.
| Item | Estimated Cost |
|---|---|
| New OEM (Mopar) | $95 - $150 |
| New Aftermarket | $44.73 - $97.75 |
| Shop Labor | $150 - $300 |
Frequently Asked Questions (FAQ)
Where is the output speed sensor located?
On 4WD models, the sensor is on the driver's side of the transmission, near the rear where it meets the transfer case. It is notoriously difficult to reach because the transfer case shifter linkage bracket blocks access. 🎬 Watch this guide for help navigating the transfer case linkage. 2WD models have easier access as the sensor is on the transmission's extension housing.
How difficult is it to replace this sensor?
For 4WD models, this is a difficult job. The transfer case linkage bracket must be loosened or removed to get the sensor out, which can be very challenging. It is not a simple unbolt-and-replace job for most DIY mechanics. For 2WD models, the job is much easier.
Will a bad output speed sensor make my speedometer act weird?
No. A bad transmission output speed sensor will cause shifting problems. An erratic or non-working speedometer is caused by the *other* speed sensor (VSS) located on the transfer case.
Are there any recalls for this part?
No, there are no specific recalls or technical service bulletins (TSBs) from the NHTSA for the automatic transmission output speed sensor on the 1991-2001 Jeep Cherokee.
Helpful Videos
Technical Specifications
OEM Part Numbers: 4882851 4897734AA
This sensor is located on the driver's side of the AW4 automatic transmission. On later models (approx. 1998-2001), the input and output sensors are the same part. The sensor is held in by a single 10mm bolt but access is severely restricted on 4x4 models.
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.
- Jeep Cherokee:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Is Your Cherokee Shifting Strangely?
- Symptoms of a Failing Output Speed Sensor
- Don't Confuse the Two Speed Sensors!
- Choosing the Right Aftermarket Sensor
- Tier 1: OEM Equivalents
- Tier 2: Reputable Aftermarket
- Tier 3: Economy/Unknown
- Replacement Cost
- Frequently Asked Questions (FAQ)
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