DTC 74, Led Display Dimming Output CKT Open Or SHRTED To GRND: Notes

CCM supplies ground for LED dimming output circuit in the form of a Pulse Width Modulated (PWM) output through LED dim control circuit. Power is supplied to LCD dim control circuit internally through headlight switch, radio control head and heater/air conditioning control head (if equipped with electronic heating/air conditioning).

DTC 74 will set when:

• Ignition 3 is on.
• Headlights and parking lights are on.
• PWM dimming control is not set for zero or 100 percent.
• No transition is captured over a specific time span at CCM terminal D2.
• PWM feedback shows a high logic state over the complete capture time.
• If an after market radio is installed and original radio control head dimming control lines have been left open, DTC 74 may set.

When DTC 74 is set, SYS will flash. If LED dim control circuit is shorted to ground, LEDs will illuminate at full bright regardless of changes in ambient light level and/or dimmer control position. If LED dim control circuit is open, LEDs will not illuminate. If an open or short to ground is present in LED dim control circuit, wiring problem is most likely located in circuit between CCM and splice where circuit branches off to individual components.

DTC 74 will clear when:

• Ignition 3 is off.
• Headlights and parking lights are off.
• PWM dimming control is set for zero or 100 percent.
• A transition is captured over a specific time span at CCM terminal D2.
• PWM feedback does not show a high logic state over the complete capture time.