Reference and speed sensors testing

The crankshaft reference and speed sensor wiring harnesses are routed around the left side of the engine and lead to connectors above the left fuel rail. The wires are marked with tape collars.

Sensor Wire Markings

• Reference sensor BG

When testing the sensors, the temperature should be approximately 77°F (25°C) to obtain the most accurate results.

Detach sensor electrical connectors located on left side of engine.

• Check resistance between sensor terminals.

• Correct resistance values are given in Table c.

The two sensors are electrically identical.

Table b. Reference or Speed Sensor Terminal Resistance



1 and 2

960 ± 96 £2

1 and 3

> 100,000 ii

2 and 3

> 100,000 a

1984 Porsche 911 Speed Sensor


Porsche944 Crack Sensor

— Remove sensors, as described later.

• Check for dents or cracks in sensors, or chafed spots in wiring.

Foreign material in the bellhousing can destroy a sensor.

If no faults are found with reference sensor or speed sensor, inspect raised pin on flywheel (arrow).

• Use wrench on front crankshaft pulley to hand turn engine clockwise until pin is visible through hole at bottom of bell-housing.

• If pin is damaged or missing, it should be replaced with an original pin available from a Porsche dealer.

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