Guide to the 1990-1994 INFINITI Q45 Engine Coolant Temperature Sensor
Poor performance or bad fuel economy in your Q45 could point to a failing engine coolant temperature sensor.
- The ECT sensor is critical for fuel economy and performance in your Q45.
- There are two sensors; make sure you are replacing the correct one (the two-wire sensor for the ECU).
- Stick with reputable aftermarket brands like Beck Arnley, Delphi, NGK, or Standard Ignition for reliability.
- Be very gentle with the old, brittle plastic connector during replacement.
Is Your Q45 Running Rough? It Could Be the Coolant Sensor
The first-generation INFINITI Q45 is a classic, but its complex systems require all sensors to work correctly. A faulty Engine Coolant Temperature (ECT) sensor can cause a variety of problems that might seem unrelated. Because the sensor's reading affects how much fuel the engine gets, a bad sensor can make your Q45 run too rich (too much fuel) or too lean (not enough fuel). This can lead to poor gas mileage, a rough idle, and even stalling.
Two Different Sensors
Your Q45 has two temperature sensors. One is the Engine Coolant Temperature Sensor, which sends information to the ECU. The other is the Temperature Sender, which only operates the temperature gauge on your dashboard. This article focuses on the ECT sensor for the ECU, which is the one that affects engine performance.
Choosing the Right Aftermarket Sensor
When replacing the ECT sensor on your 1990-1994 Q45, you have options ranging from budget-friendly to premium aftermarket. For a critical sensor like this, quality matters.
- Premium Brands (Beck Arnley, Delphi, NGK, Standard Ignition): These brands are often trusted in the aftermarket. Beck Arnley is known for sourcing parts that match original equipment (OE) form and function. Delphi and NGK are also well-regarded OEM suppliers. Standard Motor Products (SMP) is a long-standing aftermarket manufacturer with a reputation for quality parts, often considered better than basic consumer-grade options. These are your safest bet for reliability and a proper fit.
- Mid-Tier Brands (Walker Products, Hella, Four Seasons): These brands can offer good value. They are generally reliable, though they may not have the same stringent OE-matching process as the premium brands.
- Value Brands (URO Parts, Facet, Global Parts, Skyward, True Tech): These brands offer the lowest prices. While tempting, the quality can be inconsistent. Some users report success with URO Parts on non-critical components, but others advise against using them for critical systems like engine management due to higher failure rates. For a sensor that plays a key role in engine performance, it's often wise to spend a little more on a premium or mid-tier brand to avoid replacing it again soon.
A Note on Connectors
After decades of heat cycles, the plastic electrical connector for the ECT sensor on your Q45 can become very brittle. Be extremely careful when disconnecting it. If it breaks, you will need to source a replacement connector pigtail and splice it into your engine harness.
Known Issues & Recalls
Searches for recalls and Technical Service Bulletins (TSBs) related to the Engine Coolant Temperature Sensor on the 1990-1994 INFINITI Q45 did not yield any specific results. There was a recall for some 1991-1992 models related to the rear speaker amplifiers, but it is unrelated to the engine management system. The primary issues reported by owners in forums are related to normal age-related failures of the sensor and the brittleness of its plastic connector.
Frequently Asked Questions
Where is the ECT sensor located on the 1990-1994 Q45?
The ECT sensor for the ECU is typically located on the front of the engine, on the coolant crossover pipe or near the thermostat housing. It is the sensor with a two-wire connector. The single-wire sensor is usually the sender for the dash gauge.
Can I replace this sensor myself?
Yes, this is a DIY-friendly job for most home mechanics. It requires basic hand tools. The main challenges are accessing the sensor and being careful with the old plastic connector. You will lose some coolant during the swap, so have a drain pan ready and be prepared to top off the coolant afterward.
What happens if I don't replace a bad ECT sensor?
Ignoring a faulty ECT sensor can lead to persistently poor fuel economy, failed emissions tests, and potential long-term damage to your catalytic converters from running too rich. It can also cause frustrating driveability issues like hard starting and stalling.
Should I buy an OEM sensor or is aftermarket okay?
For this part, a high-quality aftermarket sensor from a reputable brand like Beck Arnley, Delphi, NGK, or Standard Ignition is a reliable and cost-effective alternative to a more expensive OEM part. These brands often meet or exceed OEM specifications. Cheaper, value-line parts may be less reliable and are not recommended for this critical component.
Technical Specifications
OEM Part Numbers: 22630-44B10 22630-44B20 22630-71L00
The sensor for the ECU has a two-pin connector. The sensor for the gauge typically has a single-pin connector.
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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.
- INFINITI Q45: