Cummins ISB CM550 (1990-94) Fault Code: 431 PID: 91 SPN: 91 FMI: 4 Idle Validation Switch (IVS) Circuit

Description

Circuit Description
The idle validation switch (IVS) is used by the electronic control module (ECM) to indicate
when the accelerator pedal is released (on-idle) or depressed (off-idle). The switch is adjusted
by the accelerator pedal manufacturers to switch from on-idle to off-idle at the correct
accelerator pedal position.

NOTE: The connector pin letters shown for the accelerator pedal wiring in these
troubleshooting steps are examples of representative sensors. The connector pin assignments
can vary with the equipment manufacturer, but the base troubleshooting logic will still apply.

Component Location
The idle validation switch is located on the accelerator pedal assembly.

Shop Talk
This fault code is usually caused by a loose connection, uncalibrated accelerator pedal, or miswired IVS.
A bad ground on pin A of the IVS can also cause this fault.