Engine Management Sensors: Crank, Cam, MAP, MAF and Lambda

Modern engines run closed-loop on sensor data. Crank-position sensor tells the ECU exactly where the crank is at any moment. Cam-position sensor confirms the relationship between cam and crank. MAP sensor reads intake manifold pressure. MAF sensor measures intake air mass. Lambda (oxygen) sensors at one or two points in the exhaust report combustion completeness. Each is a precision component, and each can drift or fail.

Crank and cam position sensors

Inductive or Hall-effect sensors reading toothed rings on the crank pulley and cam pulley. Failure: hard starting, intermittent stalling, no-start with a clear fault code. Replacement is straightforward when access is good.

MAP and MAF sensors

MAP measures intake manifold absolute pressure. MAF measures mass airflow at the intake. Both feed fueling calculations. Failure of either causes rough running, fault codes, fuel-economy drop. MAF sensors are particularly vulnerable to dust contamination from a torn air filter.

Lambda sensors

Two on most cars — one before the catalyst (controls fueling), one after (monitors catalyst efficiency). Lambdas drift with age — typically 60,000-100,000 mile life. Failure: fuel-economy drop, emissions-test fail, fault code.

Brand

Bosch, NTK, Denso, Hella, VDO supply OE on most applications. NTK is OE on many Japanese lambda sensors and a strong choice across European applications. Match by OE part number — sensor connectors and wire lengths vary per car.

Find engine management sensors for your car on the Engine Management Sensors collection. The ECU is only as good as its sensors.