Engine Camshaft Position Sensor: A Guide for the 2002-2006 Chevrolet Trailblazer EXT
Fix stalling, rough idling, and starting problems on your Trailblazer EXT by understanding and choosing the right camshaft position sensor.
- A failing sensor is a very common cause of stalling and no-start issues on the Trailblazer's 4.2L engine.
- The primary trouble code associated with this failure is P0340.
- For best results, use a premium aftermarket brand like Delphi (the OEM supplier) or ACDelco, as these engines are sensitive to sensor quality.
- Replacement is a simple, 30-minute DIY job with a single 10mm bolt located at the front-passenger side of the engine.
Is Your Trailblazer EXT Stalling or Running Rough?
A common failure point on the 4.2L inline-6 engine in the 2002-2006 Trailblazer EXT is the camshaft position sensor. When this small electronic part starts to fail, it can cause frustrating and sometimes dangerous problems, like stalling in traffic. Symptoms often appear without warning and can include a Check Engine Light, difficulty starting the engine, and a noticeable loss of power. Fortunately, this is a straightforward and affordable repair you can often do yourself.
Common Symptoms of a Bad Camshaft Sensor
- Stalling: The engine may stall unexpectedly, especially when coming to a stop or at idle.
- Check Engine Light: The most common sign is a check engine light with code P0340.
- Hard Starting or No Start: The engine may crank for a long time before starting, or it may not start at all.
- Rough Idle: The engine may vibrate or run unevenly when the vehicle is stopped.
- Poor Acceleration: You might notice the vehicle feels sluggish or lacks power when you press the gas pedal.
Choosing the Right Aftermarket Sensor
When it comes to electronic parts on the Trailblazer's 4.2L engine, quality matters. Forum discussions among owners frequently show that these engines can be very picky about their sensors. While many brands are available, they generally fall into three tiers.
Tier 1: OEM & Premium Aftermarket
These are the most recommended options for reliability and preventing a repeat failure. They are designed to meet or exceed original factory specifications.
- Delphi: Delphi is widely reported to be the Original Equipment Manufacturer (OEM) for General Motors for this part. Choosing a Delphi sensor is like getting the genuine GM part without the dealership price tag. It is a highly trusted option for a direct fit and reliable performance.
- ACDelco: As GM's own parts brand, ACDelco is another top-tier choice that guarantees OEM fit, form, and function.
- NGK/NTK & Hitachi: Both are well-respected Japanese brands known for producing high-quality electronic components that often rival OEM parts in performance and longevity.
Tier 2: Standard Aftermarket
These brands offer a good balance of price and quality and are a significant step up from basic economy parts.
- Standard Motor Products (SMP): A long-standing brand in the aftermarket, offering reliable parts that are a popular choice for general repairs.
- Dorman: Dorman is known for making a wide range of aftermarket parts. While popular, some owners have reported mixed results with sensitive electronics, sometimes needing to replace them sooner than an OEM or premium part.
- Walker Products: Another established brand that provides a functional and affordable replacement option.
Tier 3: Economy Brands
This category includes brands like URO Parts, Prenco, Skyward, and other private labels. While they are the most budget-friendly, their long-term reliability can be inconsistent for sensitive electronics. They might solve the problem initially, but some owners report having to replace them again with a premium brand after a short time. If you are on a tight budget, they can work, but be aware of the potential trade-off in durability.
Cost to Replace the Camshaft Position Sensor
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket | $21 - $75 |
| New OEM (ACDelco/GM Genuine) | $50 - $90 |
| Shop Labor | $50 - $100 |
| Total Professional Replacement | $71 - $190 |
Frequently Asked Questions
Where is the camshaft position sensor located on the 2002-2006 Trailblazer EXT?
The sensor is located on the front of the engine, on the passenger side of the cylinder head, near the power steering fluid reservoir. It is held in place by a single 10mm bolt.
Can I replace this sensor myself?
Yes, this is a very beginner-friendly repair. The job requires only basic tools (a 10mm socket and ratchet) and typically takes less than 30 minutes. You simply disconnect the electrical connector, remove one bolt, and swap the old sensor for the new one. It's a good idea to apply a small amount of clean engine oil to the new sensor's O-ring before installation.
Are there any recalls for this part?
A search of the National Highway Traffic Safety Administration (NHTSA) database shows no open recalls for the camshaft position sensor on the 2002-2006 Chevrolet Trailblazer EXT.
What happens if I don't replace a failing sensor?
If you continue driving with a bad camshaft position sensor, you will likely experience worsening symptoms like frequent stalling, which can be a safety hazard in traffic. It can also lead to a no-start condition, leaving you stranded. Addressing it promptly is recommended.
Technical Specifications
OEM Part Numbers: 12571266 12584079 12568715
3-Pin Connector, Hall Effect Sensor, O-Ring Seal
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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.
- Chevrolet Trailblazer EXT:
- 🛍️ Shop This Part
- Is Your Trailblazer EXT Stalling or Running Rough?
- Common Symptoms of a Bad Camshaft Sensor
- Choosing the Right Aftermarket Sensor
- Tier 1: OEM & Premium Aftermarket
- Tier 2: Standard Aftermarket
- Tier 3: Economy Brands
- Cost to Replace the Camshaft Position Sensor
- Frequently Asked Questions
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