Rough road signal (Engine management system - V8)

In the case of a VSS failure on vehicles with automatic gearboxes, the ECM applies default values derived from the EAT ECU. There are no default values for manual gearbox vehicles.

The VSS can fail in the following ways: l Wiring short circuit to vehicle supply. l Wiring short circuit to vehicle earth. l Wiring open circuit.

In the event of a VSS failure, any of the following symptoms may be observed: l MIL illuminated after 2 driving cycles (NAS only). l Vehicle speed limiting disabled (manual transmission vehicles only). l SLABS/HDC warning lamp on and audible warning.

Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by TestBook:

Rough road signal

When the vehicle travels across rough terrain, or on rough roads instability becomes evident in the drive train. The ECM could interpret these vibrations as a 'false misfire'. To counteract this 'false misfire' the SLABS ECU generates a rough road signal, sends it to the ECM so that the ECM can suspend misfire detection for as long as the vehicle is travelling on the 'rough road'.

Function Input for the rough road signal is measured via pin 34 of connector C0637 of the ECM. The SLABS ECU generates a PWM signal that varies in accordance with changing road conditions. The rough road PWM signal operates at a frequency of 2.33 Hz ± 10%. The significance of changes in the PWM signal are shown in the following table:

The rough road signal can fail in the following ways: l Harness or connector damage l SLABS failure — wheel speed sensor

A rough road signal failure may be evident from the following: l HDC / ABS warning light on