Diagnostic trouble code (DTC) information

Condition

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

Courtesy of VOLVO CARS OF NORTH AMERICA.

If the electronic throttle module (ETM) detects that the engine control module (ECM) sends information that cruise control is active even though the brake light switch is active or that there is a fault detected in the throttle unit that does not allow cruise control to be active, this information is sent to the engine control module, which then stores diagnostic trouble code ECM-91CF.

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

Closing of throttle during braking.

The accelerator pedal position is ignored when the brake pedal is depressed.

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.

Fuel cut-off that follows accelerator pedal position.

Engine speed is regulated via fuel cut-off by deactivating the injectors one at a time. Engine speed is determined by gas pedal position sensor position and engine speed is maximized to about 5000 RPM. This reconfiguration can cause the engine to idle very unevenly since the engine control module (ECM) regulates engine speed by cutting of the fuel to the cylinders individually. Do not confuse this reconfiguration (engine behavior) with an actual driveability problem that was present before reconfiguration.

For upgraded software, released in 2006 or later, adjustments have been made to substitute values. In driving cycles when the fault is active, the throttle will follow the accelerator pedal position and cruise control will not be possible to activate. Identifying upgraded software ECM/ETM

Possible Source

open-circuit, short-circuit to supply voltage or short-circuit to ground in signal cable for the stop lamp switch between the engine control module (ECM) and throttle unit
defective engine control module (ECM)

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

For turbo engines and 6-cylinder aspirated engines: Information about combined diagnostic trouble codes (DTCs)

For 5-cyl. normally aspirated engines. Information about combined diagnostic trouble codes (DTCs)

Fault symptom[s]

the accelerator pedal (AP) is ignored when braking
the cruise control cannot be activated
the ETS warning lamp lights (C70 and S/V70 -2000 only).