Cummins ISB CM550 (1990-94) Fault Code: 131 PID: 91 SPN: 91 FMI: 3 Accelerator Position Sensor Circuit

Circuit Description
The accelerator position sensor is attached to the accelerator pedal. The accelerator position
sensor sends a signal to the electronic control module (ECM) when the driver pushes on the
accelerator pedal. The accelerator position circuit contains three wires: a +5-VDC supply wire
(pin 29), a return ground (pin 19), and a signal wire (pin 30).

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 equipment manufacturer, but the base troubleshooting logic will still apply.

Component Location
The accelerator position sensor is located on the accelerator pedal.

Shop Talk
If all wiring and sensor checks look in good order then replace the accelerator position sensor
and the idle validation switch circuit wires between the accelerator pedal and the ECM with
new wires. Run the wires through, or around, the bulkhead without using the bulkhead
connector. Test the truck with the test wires in place. If the fault goes away, replace the OEM
harness. Seal the openings in the bulkhead around the connector and wires to prevent toxic
and noxious fumes from entering the operator area.

NOTE: The three wires in the accelerator position sensor circuit must be twisted together. The
same applies for the three wires in the idle validation switch circuit.

NOTE: If pin 19 (return) and pin 30 (signal) are reversed, throttle position will only read 50
percent.