LH 2.4 temperature sensor resistance values

The engine temperature sensor (ECT) is a critical component for mixture formation. If the sensor provides wrong information, the engine may run too rich (as if choked) or a lean mixture may cause starting problems when warm.

In Volvo 200/700/900 series in-line engines, there are two different temperature sensors on the side of the block: Instrument cluster sensor: Located in a more easily accessible location (usually around cylinder 2). This only controls the dashboard gauge. Engine management (LH 2.4) sensor: Located in a more difficult spot under the intake manifold, usually around cylinder 3 or 4. This is the sensor that affects engine operation.

You can verify sensor functionality with a multimeter, either directly from the sensor terminals or from the engine control unit (ECU) connector: Measure resistance (ohms) from each sensor terminal directly to ground (chassis). Important: You should get nearly identical values from each terminal at the same temperature.

Sensor resistance changes with temperature. The hotter the engine, the lower the resistance. Temperature (°C) Resistance Value (Ω / Ohms) -20 °C / approx. 15,000 Ω (15 kΩ) 0 °C / approx. 5,700 Ω (5.7 kΩ) +20 °C / approx. 2,500 Ω (2.5 kΩ) +40 °C / approx. 1,100 Ω (1.1 kΩ) +80 °C / approx. 300 Ω +100 °C / approx. 150 Ω

Yes. For example, Volvo 740's Motronic system uses the same sensor type, so the values above apply to it as well.

Infinite resistance: Sensor is broken or connector is loose. The engine thinks it's in "eternal winter" and delivers too much fuel. Zero (or very low resistance) when cold: Sensor is shorted. The engine thinks it's hot, which makes cold starting difficult. Tip: Also check the wiring harness condition. If wires are too tight or broken under the intake manifold, the signal may be intermittent or ground out to the chassis.