Engine Speed Signal: Description

The engine speed signal is sent by the ECM to the instrument pack, Body Control Module (BCM) and SLABS/ABS control module via a direct hardwired connection.

The ECM has power stage diagnostics for this signal. See Fig 1 . A fault is detected if any of the following conditions is satisfied:

1. Engine speed signal driver short circuit to battery positive, i.e. the driver voltage is greater than half the battery voltage when the driver is on.
2. Engine speed signal driver short circuit to ground, i.e. the driver voltage is less than one third of the battery voltage when the driver is off.
3. Engine speed signal driver open circuit, i.e. the driver voltage is greater than one third of the battery voltage but less than two thirds of the battery voltage when the driver is off.

Fig 1: Engine Speed Signal DTC Testing

Courtesy of LAND ROVER NORTH AMERICA, INC.