Electrical issue Check engine light does not work thus the brain does not sense problems in the system and cannot right itself. Also the tow/haul doesn't engage when the shifter button in pushed but when the truck loses power due to a dead battery (battery brand new) when vehicle is powered up again after a jump or full charging the tow/haul dash symbol is on and engaged. Shifter button does not work to disengage it, the key has to be turned off to disengage the tow/haul. There is a major electrical short but where is it?

limited info generic answer ---tow--haul switch doesnt have auto level thats a separate system --have scanned for any codes active or pending check fuses relays and sensors

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) 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.

Would't trust it , take an have DTC'S - diagnostic trouble codes checked by a qualified repair shop with a factory or professional scan tool . Auto part stores can not check BCM code's .
DTC B2722

Tow/Haul Switch/Indicator Always On or Inoperative

Step
Action
Value(s)
Yes
No
1
Install a Scan Tool .
Turn ON the ignition, with the engine OFF.
Cycle the tow/haul switch while observing Tow/Haul Mode on the Scan Tool .
Does the Scan Tool display Active when the switch is first pressed, and then Inactive when the switch is pressed again?
--
Go to Intermittent Conditions in Engine Controls - 4.3 L or Intermittent Conditions in Engine Controls - 4.8 L, 5.3 L and 6.0 L
Go to Step 2

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:
- B0951
- B2610
- B2625

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
http://www.bbbind.com/free_tsb.html 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

That light means that the shift points have changed on the transmission. This is to get better economy when hauling. If it wont stop flashing then there is a valve in the transmission that is bad or sticking. You will have to have it removed and overhauled..

run the fault codes
check for problem torque converter servo/ solenoid , VSS or TCM units

could be the switch or modual.check wiring for worn through or earthing.

you are in fact overloading your L200 by towing a caravan,the weight your towing is about 1.5-2 tons which is more than a 1ton truck should be hauling.the extra weight causes the motor to work harder thus run hotter and is why it doesn`t overheat when not towing it.the only common denomenator is you towing the van.thus the van is too heavy for your vehicle to tow without any problem.

You either have a bad switch or the wires have lost contact.
The tow/haul switch is part of the shift lever and is not replaceable without changing the shift lever. The electrical connector is located inside the steering column covers. These wires have been known to part.

there are like 4 small wires in the lever and one is probably not connected . sounds like when you pushed the button it might of lost contact so you cant turn it off. try removing the power wire off your battery then re-connecting it. this should re-set your computer thus not showing you in tow haul mode untill you push it again.

Hi, the problem is when you are tilting the steering wheel all the way up it's putting to much tenstion on the wires that come outof your shifter that run to the tow/haul button. i am 99% sure your wires are disconected. rewire them and add some extra wire so next time there will be more slack in your wires.