Sensors (Temp, Pressure, Position)

The classic crankshaft position sensor failure. As the sensor heats, an internal fault opens the circuit, the control unit loses its reference and stops fuelling and ignition, and once everything cools the sensor works again. It is a distinctive pattern because it is heat related rather than random. Before ordering, inspect the sensor's wiring and connector, since a chafed lead near the exhaust produces exactly the same intermittent behaviour and is a common reason a replacement sensor fails again.

Usually because the wiring rather than the sensor is at fault. These sensors sit in hot, vibrating locations near the engine, and their leads chafe against brackets, harden with heat and take up oil or coolant from nearby leaks, all of which produce intermittent signals indistinguishable from a failing sensor. Water in the connector corrodes the pins to the same effect. Before fitting a second replacement, inspect the whole lead, check the connector for contamination, and reroute or repair as required.

Sometimes, and it depends on the type. A magnetic position sensor whose tip has collected metal debris often works perfectly once wiped clean, and a connector with light corrosion can be cleaned and protected. What cannot be cleaned back to health is a thermistor whose element has drifted, a pressure sensor whose diaphragm has failed, or a sensor contaminated internally by oil. Cleaning costs nothing to try on the tip and the connector, and it saves a proportion of orders outright.

Check whether the same sensor feeds both the gauge and the control unit, since many vehicles use one coolant temperature sensor for everything and others use separate senders. A sensor reading high makes fans run constantly and the mixture lean. One reading low does the opposite and can prevent the vehicle leaving its warm up strategy. Compare the sensor's reported value on a scan tool against an infrared reading of the housing, which settles it quickly and costs nothing.

Treat it as serious until proven otherwise, and prove it with a mechanical gauge rather than by replacing the switch. The switch or sensor is the cheaper part and fails often, but the consequence of ignoring a genuine low pressure warning is a destroyed engine within minutes. Fit a mechanical gauge at the sender port, read the actual pressure hot and cold, and only then decide whether you have an electrical fault or a lubrication one.

This is one of the cheaper categories on the site. Temperature sensors, pressure switches and position sensors sit at the low end of the range, and even combined pressure and temperature units remain modest. The live minimum and maximum are shown in the band at the top of this page. Because sensors are inexpensive and their symptoms are often caused by wiring, the diagnostic effort matters more than the price comparison here.

Because the sensor sits behind the front bumper where it picks up radiated heat from the road and the vehicle ahead when airflow stops. Most vehicles apply a filter that holds the reading down while stationary and updates it as you move, so a display that climbs in a jam and falls once moving is behaving normally. A reading that is consistently wrong at road speed, or that never changes, is a genuine fault and points at the sensor or its wiring.

Most of them, yes, and the main considerations are access and torque. Work on a cool engine where the sensor sits in coolant or oil, catch the fluid that escapes, and torque the sensor to specification rather than tightening it hard, since overtightening distorts the housing and can damage the element. Route the lead exactly as the original ran and secure it in its clips, because the routing is what keeps the next sensor alive.

Not reliably. Sensors that share a thread and a connector shape can differ in resistance curve, pressure range and output scaling, and the control unit has no way of knowing it is being told a plausible lie. The result is a reading that looks reasonable and is wrong, with no fault code to reveal it. Match the OE number rather than the physical dimensions, and use the quote form where the reference brings back nothing.

It is a single unit measuring two quantities, typically pressure and temperature in the same location, reporting both to the control unit through one connector. Manufacturers use them to reduce ports, connectors and wiring, and they are common in air conditioning and thermal management circuits. The practical consequence is that a failure of either function means replacing the whole unit, and that it cannot be substituted with two separate sensors even where the readings are the same.

A different set of them. Crankshaft, camshaft, knock and oil sensors belong to combustion engines and disappear entirely. What multiplies instead is thermal sensing: coolant temperatures at several points around the drive unit and the pack, refrigerant pressure and temperature in the air conditioning and heat pump circuits, and cabin sensing for the climate system. Those sensors matter more than their equivalents did, since thermal management governs both performance and charging speed.

Yes. This group holds hundreds of small references and the slower moving ones are frequently unpriced. Quote the number and a figure follows. Take care with the two in one sensors, where temperature and pressure share a housing, because they look like the single function version and carry a different connector and a different signal. Check the reluctor wheel while you are ordering a crankshaft or camshaft position sensor. A cracked or contaminated trigger wheel produces exactly the same intermittent signal as a failing sensor, and a new sensor reading a damaged wheel changes nothing at all.