Diagnostic trouble code (DTC) information

Condition

Fig 1: Identifying Communication Signals Between Electronic Throttle & Brake Pedal Systems

Courtesy of VOLVO CARS OF NORTH AMERICA.

All communication between the cruise control buttons in the steering wheel (steering wheel module (SWM)) and the engine control module (ECM) occurs via the central electronic module (CEM) and the CAN network. Both Engine control module (ECM) and Steering wheel module (SWM) check that the buttons function as they should and check that the information from the buttons seems reasonable. Engine control module (ECM) performs the following checks of the information that comes via the CAN-network:

When information about the buttons' positions is sent from Steering wheel module (SWM), a checksum is attached, which is based on the button information in the message. Then when the message reaches Engine control module (ECM), the Engine control module (ECM) calculates its own checksum based on the button information, and compares it with the attached checksum from the steering wheel module (SWM). If Engine control module (ECM) registers that these two checksums do not match for longer time than 0.1 seconds, then ECM-922A, Faulty signal, is stored.
Button information from Steering wheel module (SWM) is updated the whole time on the CAN-network, even if it is the same value that is sent every time. Therefore Steering wheel module (SWM) attaches information about the value being updated every time that it is updated. If Engine control module (ECM) registers that update information from Steering wheel module (SWM) is missing for longer time than 0.8 seconds, then diagnostic trouble code ECM-922A, Faulty signal, is stored.

For upgraded software, released during year 2006 or later, certain adjustments have been made. Above detection times have been increased from 0.1 and 0.8, respectively, to 0.9 seconds. Another condition is that vehicle speed shall be higher than 25 km/h (15 mph) for above tests to be active, which is different from earlier software, where there is no condition for vehicle speed.

See Identifying upgraded software ECM/ETM

For more information about the electronic throttle system and related components such as the electronic throttle module, accelerator pedal position sensor, brake light switch, clutch pedal position sensor, and brake pedal position sensor:

See Design
See Function

Substitute Value

Cruise control off.

Cruise control off during entire operating cycle in which fault was detected. If the fault is no longer present, the function is available the next time the car is started.

Possible Source

defective steering wheel module
incorrect system voltage.

This diagnostic trouble code is generated in combination with other trouble codes. Information on the possible root cause is described.

See Information about combined diagnostic trouble codes (DTCs)

Fault symptom[s]

general orange warning lamp lit
cruise control does not function at all.