A Guide to the Throttle Position Sensor for the 2008-2009 Pontiac G8
Experiencing reduced power or a rough idle? Your G8's throttle position sensor may be the cause.
- A "Reduced Engine Power" warning is the most critical symptom of a failing TPS.
- You can choose to replace only the aftermarket sensor, which is more affordable than replacing the entire throttle body assembly.
- After replacement, the vehicle requires a 'relearn' procedure, which can be done with a scan tool or through normal driving.
- If replacing the entire throttle body on a G8 GT, verify you have the correct 'silver' or 'gold' blade version for your model year to avoid issues.
Is Your G8's Throttle Position Sensor Failing?
When the throttle position sensor begins to fail, your car's computer gets confusing signals. This can cause a number of noticeable problems. The most common and serious symptom is the "Reduced Engine Power" message appearing on your dashboard. This is a safety feature, often called 'limp mode,' that drastically limits speed and acceleration to prevent potential engine damage.
Other common symptoms include:
- Check Engine Light is on
- Hesitation or stumbling when you accelerate
- Rough or unstable idling
- Engine stalling, especially when coming to a stop
- Harsh or delayed automatic transmission shifts
- Poor fuel economy
Important: Sensor-Only vs. Full Throttle Body Replacement
From the factory, the throttle position sensor on the G8 is considered part of the complete throttle body assembly. For years, the standard dealer repair was to replace the entire unit. However, the sensor is a common failure point, and the aftermarket now offers standalone replacement sensors. Furthermore, General Motors issued a Special Coverage bulletin (14582A) that allows for a sensor-only replacement on affected vehicles, confirming it is a valid repair procedure. This gives you a choice: replace just the failing sensor for less money, or replace the entire throttle body assembly.
Choosing the Right Aftermarket Part
When shopping for a new aftermarket sensor, you have several reliable options. The key is to choose a brand known for quality electronic components.
- NGK (NTK): As a major OEM supplier for many car brands, NTK sensors are a trusted choice. They are engineered to meet or exceed original specifications and often come with a strong warranty.
- Standard Ignition (Standard Motor Products): SMP is another long-standing, reputable aftermarket manufacturer that produces reliable sensors and other engine management parts.
- Motorad & Global Parts: These brands provide a cost-effective alternative for your repair.
Pro Tip for G8 GT Owners
If you decide to replace the entire throttle body on a G8 GT, be aware of a key difference. Early 2008 models used a throttle body with a "silver" blade, while later models used a "gold" (brass) blade that operates differently. Installing the wrong assembly without a corresponding computer tune can cause calibration problems. Always verify you are purchasing the correct part for your specific vehicle year.
Cost of Replacing the Throttle Position Sensor
| Part / Service | Estimated Cost |
|---|---|
| New Aftermarket Sensor | $67.73 - $82.50 |
| New OEM Sensor Kit | $100 - $150 |
| New Aftermarket Throttle Body Assembly | $90 - $230 |
| New OEM Throttle Body Assembly | $315 - $595 |
| Shop Labor | $75 - $160 |
Cost estimates are for parts and labor only and do not include taxes, fees, or diagnostic charges. Prices can vary by location and supplier.
Frequently Asked Questions
What is the "Reduced Engine Power" warning?
This is a safety mode triggered by the vehicle's computer when it detects a serious fault in a system like the electronic throttle control. It limits engine power and speed to allow you to drive slowly to a safe location or repair shop, while protecting the engine from further damage. A faulty TPS is a very common cause of this warning on the G8.
Does a new throttle position sensor need to be calibrated?
Yes. After replacing the sensor or the entire throttle body, the engine's computer needs to learn the new sensor's baseline readings. This is called a "Throttle Learn" or "Idle Learn Reset." A repair shop can do this instantly with a scan tool. It can also be learned over several drive cycles, though you may experience a rough idle or have a temporary Check Engine light during this period.
Can I just clean the throttle position sensor?
No. The throttle position sensor is a sealed electronic component that cannot be cleaned. While cleaning carbon buildup from the throttle body bore and blade can solve some idling issues, it will not fix a failed sensor. If the sensor itself is faulty, it must be replaced.
What is GM Special Coverage 14582A?
This was a program issued by General Motors to address widespread issues with the throttle position sensor on the G8 and other models. It extended the warranty for this specific failure to 10 years or 120,000 miles. Under this program, dealers were instructed to install a sensor-only repair kit, validating it as a proper fix. While this coverage has likely expired for most vehicles due to age, it confirms that replacing only the sensor is a viable and manufacturer-approved repair strategy.
Technical Specifications
OEM Part Numbers: 19420707 12605109 19420034 12570790
The throttle position sensor for the 2008-2009 Pontiac G8 is an electronic sensor integrated into the throttle body housing. It communicates throttle angle to the ECM to manage the engine's drive-by-wire system.
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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.
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