A Guide to the Engine Camshaft Position Sensor for the 1999-2003 Audi S4
Solve starting issues and poor performance by understanding, diagnosing, and replacing the right camshaft position sensor for your B5 S4 2.7T engine.
- A failing camshaft position sensor will cause stalling, hard starts, and a check engine light with codes P0341 or P0346.
- For reliability on the 2.7T engine, it is highly recommended to use the OEM supplier brand, Bosch.
- DIY replacement is possible, but the driver's side (Bank 2) sensor is in a very tight location requiring patience.
- Ignoring a failing sensor will eventually lead to a no-start condition, leaving you stranded.
Is Your Audi S4 Stalling or Hard to Start? It Could Be the Camshaft Position Sensor.
A failing camshaft position sensor is a common issue on the B5 Audi S4 that can cause a range of frustrating problems. This sensor, also called a Hall sender, tells your engine's computer where the camshafts are in their rotation. When it starts to fail, the computer gets bad information, leading to poor engine performance. Symptoms can start small but will get worse, potentially leaving you stranded.
Symptoms of a Bad Camshaft Position Sensor
- Check Engine Light: This is often the first sign. You may see codes like P0341 (Bank 1) or P0346 (Bank 2). 🎬 Learn more about diagnosing and fixing the Bank 2 fault code.
- Difficulty Starting: The engine may crank longer than usual before starting, or it may not start at all. A bad sensor prevents the ECU from knowing when to fire the fuel injectors and spark plugs.
- Stalling and Rough Idle: The engine may stall unexpectedly, especially when warm, or idle roughly.
- Poor Acceleration: You might notice a lack of power, hesitation, or sputtering when you press the gas pedal.
- Reduced Fuel Economy: When the ECU can't time fuel injection correctly, it often uses more fuel than necessary.
Critical Part: OEM vs. Aftermarket Quality Matters
For critical electronic sensors like the camshaft position sensor, quality and reliability are key. While budget-friendly aftermarket options exist, many Audi owners and mechanics report that they can fail prematurely. The original equipment manufacturer (OEM) for this part is Bosch. Choosing a Bosch sensor or a high-quality OE-equivalent brand is strongly recommended to avoid having to do the job twice. Cheaper brands like URO Parts are often considered a gamble for sensitive electronics.
Choosing the Right Aftermarket Sensor for Your S4
Not all aftermarket parts are created equal. Here’s a breakdown of brand quality tiers based on owner feedback and industry reputation:
- Tier 1 (OEM Supplier): Bosch is the original manufacturer for Audi and is the safest choice for reliability and fitment.
- Tier 2 (Reputable Aftermarket): Brands like Hella, Delphi, and Spectra generally have a good reputation for producing quality electronic components that meet or exceed OEM standards.
- Tier 3 (Budget Options): Brands like URO Parts, Walker Products, and others offer significant cost savings. However, for a critical sensor on a high-performance engine like the 2.7T, these are often not recommended due to higher reported failure rates.
Typical Replacement Costs
The cost can vary depending on the brand of the part and local labor rates. The B5 S4 has two sensors, but they can be replaced individually.
| Part/Service | Estimated Cost |
|---|---|
| New OEM (Bosch) Sensor | $90 - $175 |
| New Aftermarket Sensor | $21 - $136 |
| Shop Labor | $71 - $105 per sensor |
| Total Professional Replacement | $161 - $280+ per sensor |
DIY Installation Tip
Replacing these sensors is possible for a DIY mechanic, but access is tight. 🎬 See this clever shortcut to save time during the replacement. The Bank 1 (passenger side) sensor is easier to reach than the Bank 2 (driver side) sensor, which is tucked further back. You will need to remove some plastic covers and possibly move coolant lines to get access. A T30 Torx bit is required for the retaining bolt. 🎬 Watch this step-by-step guide for a complete sensor installation. Be patient and have a magnetic tool ready to avoid dropping the small bolt.
Frequently Asked Questions
Where are the camshaft position sensors located on the 1999-2003 S4?
The 2.7T engine has two sensors. Bank 1 is on the passenger side of the engine, near the front. Bank 2 is on the driver's side, in a more difficult-to-reach position toward the rear of the cylinder head.
Do I need to replace both sensors at the same time?
No, you only need to replace the one that has failed. A diagnostic scan tool can tell you which sensor is causing the fault code (P0341 for Bank 1, P0346 for Bank 2). However, since they are the same age, the other may not be far behind.
What happens if I don't replace a failing sensor?
The symptoms will worsen over time. Eventually, the sensor will fail completely, and your engine will not start, potentially leaving you stranded. Ignoring the issue can also lead to failed emissions tests and poor engine performance.
Is a genuine Audi or Bosch sensor worth the extra cost?
For this specific part, yes. Forum discussions with experienced B5 S4 owners consistently recommend using the OEM Bosch sensor. Aftermarket sensors, especially budget brands, have a higher risk of failing quickly, which means you'll be paying for parts and labor again.
Helpful Videos
Technical Specifications
OEM Part Numbers: 058905161B
The 1999-2003 Audi S4 2.7T uses two identical camshaft position sensors (Hall senders), one for each cylinder bank. The OEM part number is 058905161B.
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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.
- Audi S4:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Is Your Audi S4 Stalling or Hard to Start? It Could Be the Camshaft Position Sensor.
- Symptoms of a Bad Camshaft Position Sensor
- Critical Part: OEM vs. Aftermarket Quality Matters
- Choosing the Right Aftermarket Sensor for Your S4
- Typical Replacement Costs
- DIY Installation Tip
- Frequently Asked Questions
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