CM850 Electronic Control System – FAULT CODE 288

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Overview

SAE J1939 Multiplexing Remote Accelerator Pedal or Lever SMALL | MEDIUM | LARGE

Circuit Description

Normally, switches, accelerators, and other components are connected to the engine ECM directly through individual wires. Multiplexing allows those same components to be hard wired to an OEM Vehicle Electronic Control Unit (VECU) or Transmission ECU in the cab. Then component values and states from components (such as sensors, accelerators, and switches) can be transmitted from the OEM VECU to the Cummins engine ECM over the SAE J1939 datalink.

Messages sent from OEM VECU’s or Transmissions ECU’s are received by the Cummins engine ECM and used for controlling the engine. The Cummins ECM and OEM VECU’s must be configured properly so that proper operation of the multiplexed components will occur.

Component Location

The engine ECM is located on the intake side of the engine. The J1939 datalink wiring and VECU location varies by OEM.

Shop Talk

This fault can occur when the OEM VECU detects an error on the remote throttle and or remote throttle enable switch. The ECM has been set up properly (components enabled and OEM VECU source addressed correctly) to receive multiplexed information for the remote throttle enable switch states and remote accelerator position over the J1939 datalink from an OEM VECU, and the OEM VECU is transmitting the message for that component. Most OEM’s will not have the circuitry to detect a remote throttle switch error.

The two types of errors that can occur for this fault are:

• The OEM VECU determines that the remote throttle signal line is shorted high or shorted low. This fault status is transmitted to the Cummins ECM on the J1939 datalink, which causes this fault to occur in the Cummins ECM.
• When the remote throttle enable switch has a shorted high or shorted low error detected by the OEM VECU. This fault status is transmitted to the ECM on the J1939 datalink, which causes this fault to occur in the ECM. Most OEM’s will not incorporate fault detection on a switch.

NOTE: It is still possible to get a Fault Code 285 or 286 if there is an incorrect setup in the OEM VECU or Cummins ECM for other components, or the remote throttle and remote throttle switch, or the datalink is damaged. OEM configurations must multiplex the remote throttle and remote throttle switch inputs together to allow the use of the J1939 multiplexing feature for these components. INSITE™ can be used to monitor multiplexed components.

Refer to Troubleshooting Fault Code t05-288