Diagnostic Trouble Code (DTC) Information

Diagnostic trouble code (DTC) information

Condition




Vehicle speed information is transmitted from the combined instrument panel to the cruise control control module.
The signal is a variable-frequency uniform square wave where frequency increases with road speed.
The control module uses the signal as a reference speed when setting and checking speed. The signal is also used to determine whether speed changes are normal.
The control module has a safety function for disengaging cruise control.
This function is activated if acceleration or deceleration is abnormal (wheel-spin) or (wheel lock-up) and when vehicle speed is less than 75% of the set speed - when driving up steep hills for example, when the engine cannot maintain vehicle speed.
Safety disengagement does not necessarily mean that the cruise control is malfunctioning.
Diagnostic trouble code (DTC) 1-1-2 is stored if the control module has disengaged cruise control for safety reasons or if the vehicle speed signal is abnormal.
The diagnostic trouble code (DTC) is only stored if the control module has received a normal vehicle speed signal during the test drive.

Possible source

An abnormal vehicle speed signal can be caused by:
- incorrectly installed or poorly suppressed accessories connected to the same vehicle speed signal or same ground terminal as the speedometer.
- different ground terminals for the control module and combined instrument panel
- intermittent short-circuit to ground or voltage in the signal cable from the combined instrument panel
- intermittent open-circuit in signal cable from combined instrument
- defective speedometer
- contact resistance in terminals.

Fault symptom[s]
- Cruise control disengages while the car is being driven.
- Speedometer reading faulty.