Which I/P lights ? Instrument cluster , radio , HVAC control panel etc.... All the I/P light's are controlled by the BCM - body control module . Do you know about electronic control modules ?
DTC B2610 Passenger Compartment Dimming 1 Circuit
The body control module (BCM) receives a variable voltage signal from the instrument panel (I/P) dimmer switch requesting to illuminate the instrument panel controls illumination lamps to a desired intensity. When this occurs, the BCM directly sends a variable voltage based on the I/P dimmer switch position on the backlight lamps control circuit, instrument panel lamps dimming control circuit, and the LED dimming signal circuit.
Voltage for the backlight lamps control circuit, instrument panel lamps dimming control circuit, and the LED dimming signal circuits is from the TBC 3 fuse 16 in the underhood fuse block directly through the BCM to these circuits.
• Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
• A short to ground in the following circuits will cause the TBC 3 fuse to open:
- The backlight lamps control
- The instrument panel lamps dimming control
- The LED dimming signal
- Battery positive voltage from the underhood fuse block TBC 3 fuse
• An open in the TBC 3 fuse will cause the BCM to set the following DTC:
DTC B2615 Passenger Compartment Dimming 2 Circuit
DTC B2620 Display Dimming Pulse Width Modulation (PWM) Input Circuit
DTC B2625 Display Dimming Pulse Width Modulation (PWM) Output Circuit
Do you know how to Test for a high resistance, an open, a short to ground, or a short to voltage in the following circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
• 5-volt reference
• The dimming input
• The dimming return
Tow/Haul mode enables the operator to achieve enhanced shift performance when towing or hauling a load. When tow/haul mode is selected, the tow/haul switch input signal to the body control module (BCM) is momentarily toggled to zero volts. This signals the powertrain control module (PCM) or transmission control module (TCM) to extend the length of time between upshifts and increase transmission line pressure. Cycling the tow/haul switch again disables tow/haul mode and returns the transmission to a normal shift pattern.
After reading all the pertinent info. to your problem, doing testing ,Checking for DTC'S -diagnostic trouble codes in the BCM , checking power and ground's for the BCM an checking voltage at the tow / haul switch to and from the BCM .is where i would start . Do you know how to do electrical testing ? Read a wire diagram ? If not there are videos on youtube for learning how to do basic automotive electrical testing , how to read wiring diagrams etc... You can find free wiring diagrams at
The only thing with this is you don't have info. saying where componet location's are . This is were factory service info would be helpful