Mitsubishi Sigma Engine Oil Pressure Switch Guide for 1989-1990 Models
Keep your Sigma's 3.0L V6 safe by understanding the signs of a failing oil pressure switch.
- A flickering or constant oil light with a normal oil level is the most common symptom of a bad switch.
- Do NOT drive with the oil pressure light on; you must confirm it's a bad sensor to avoid catastrophic engine damage.
- This is an easy and inexpensive DIY replacement, typically located near the oil filter on the 3.0L V6 engine.
- There are no recalls or TSBs for this specific part; it is a standard wear-and-tear component.
Is Your Oil Light On? Understanding the Symptoms
A failing oil pressure switch on the Mitsubishi Sigma can create confusing and alarming symptoms. Because the 3.0L 6G72 V6 is known to be a reliable engine, a sudden oil light is often due to this simple sensor failing rather than a major internal engine problem, especially if the oil level is correct. Be aware of these common signs:
- Flickering or Constant Oil Light: The most common symptom is the red oil pressure light on the dash flickering or staying on, especially at idle or during turns, even when you've checked the dipstick and the oil level is full.
- Oil Leak from the Switch: These switches can fail by leaking oil. You may notice a small oil drip on the garage floor or see oily residue around the sensor itself where it screws into the engine block near the oil filter. The leak often comes from the plastic electrical connector part of the switch.
- Warning Light Never Comes On: A less common failure is when the switch breaks in the 'off' position. You can test this by turning the key to the 'ON' position without starting the engine. The oil light should light up and then go out after the engine starts. If it never comes on, the switch or the bulb may be bad.
Stop Driving Immediately
If your oil pressure light comes on, you must pull over and turn off the engine as soon as it is safe to do so. You cannot know if it's a cheap, faulty switch or a true lack of oil pressure that will destroy your engine in minutes. Always verify the oil level first.
Choosing the Right Aftermarket Oil Pressure Switch
For a vehicle like the 1989-1990 Sigma, original Mitsubishi parts are often discontinued. The aftermarket is your only realistic option. Quality varies, but even budget-friendly switches are an improvement over a faulty one. The brands are generally grouped into tiers based on reputation and materials.
Brand Quality Tiers
- Tier 1 (High Quality): Brands like Standard Ignition (SMP) and Hella are well-regarded in the industry. Standard emphasizes robust testing and the use of high-grade materials for durability. Hella is a respected German OEM supplier known for quality electronics. For a critical sensor, spending a few extra dollars for one of these brands is a wise investment.
- Tier 2 (Good Value): Facet is an established Italian brand that offers a balance of quality and price. They are generally considered a reliable choice for common repairs and are a significant step up from no-name parts.
- Tier 3 (Budget): Brands like Global Parts and Rostra Powertrain fall into the budget category. While functional, they may not have the same long-term durability or rigorous quality control as higher-tier brands. They can be a viable option if budget is the primary concern.
Pro Tip: Get the Right Tool
Replacing the switch is an easy DIY job, but you will need a special deep-well socket designed for oil pressure switches. These are inexpensive and available at any auto parts store. Using the wrong tool like pliers can damage the new switch.
Cost to Replace a 1989-1990 Mitsubishi Sigma Oil Pressure Switch
| Part/Service | Estimated Cost |
|---|---|
| New Aftermarket Part | $9.59 - $18.64 |
| Shop Labor | $50 - $100 |
| Total Estimated Cost | $60 - $120 |
Costs are estimates and may vary based on your location and the specific repair shop.
Frequently Asked Questions (FAQ)
Where is the oil pressure switch on the 1989-1990 Sigma?
On the 3.0L V6 (6G72) engine, the oil pressure switch is located on the engine block, typically near the oil filter housing. It is a small sensor with a single wire and a rubber boot connected to it.
Can I replace the oil pressure switch myself?
Yes, this is a great job for a beginner. The process involves safely raising the front of the vehicle, unplugging the electrical connector, and using a special oil pressure switch socket to unscrew the old switch and install the new one. A small amount of oil will drip out, so have a rag ready.
My oil light is on, but the oil level is full. Is it just the switch?
It is very likely the switch, as this is a common failure. However, you cannot be certain without testing. The safest approach is to assume the worst and not run the engine. A mechanic can quickly test the actual oil pressure with a mechanical gauge to confirm if the problem is the switch or a more serious issue like a failing oil pump.
Are there any recalls for the oil pressure switch on a Mitsubishi Sigma?
No, there have been no recalls or common Technical Service Bulletins (TSBs) issued by Mitsubishi or the NHTSA for the engine oil pressure switch on the 1989-1990 Mitsubishi Sigma.
Technical Specifications
OEM Part Numbers: MD138993 MD001482
Thread Size: 1/8" - 28 BSP, Connector: 1-Pin
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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.
- Mitsubishi Sigma:
- 🛍️ Shop This Part
- Is Your Oil Light On? Understanding the Symptoms
- Stop Driving Immediately
- Choosing the Right Aftermarket Oil Pressure Switch
- Brand Quality Tiers
- Pro Tip: Get the Right Tool
- Cost to Replace a 1989-1990 Mitsubishi Sigma Oil Pressure Switch
- Frequently Asked Questions (FAQ)
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