The key dance to enter the diagnostic cycle in this dishwasher is shown in the image below. The image also includes a cycle timing chart for the diagnostic test cycle and notes. I also provided a wiring diagram for the dishwasher.
The heating element is only energized for a short period of time as shown in the timing chart. You may be better able to check the heating element at the end of a heated drying cycle. There is a 6 minute delay in the drying cycle before the heating element is energized.
To properly check the heating element, I recommend
shutting off the breaker
to the dishwasher and checking the continuity through the element with a volt ohm meter. If you are able to access the wiring leads on the heating element, you can pull one of the wires off and measure the resistance through the element. If the element measures between 10 and 35 ohms of resistance, then it should be okay. An open high limit thermostat could prevent your dryer from heating as shown on the wiring diagram below. You could also have a wiring failure in the heater circuit. You can check the continuity of the heating circuit form the wires that connect to the control board (with the dishwasher breaker still off). Measure the resistance between the white/red wire of the P6 connector to the white wire on the P7 connector on the control board. You should measure between 10 and 35 ohms (the same resistance as the heating element) through this circuit. If you measure open (infinite resistance) through this circuit, then you either have an open high limit thermostat or a wiring failure. You can check the continuity of the high limit thermostat directly off the component on the outside bottom of the dishwasher sump.
This technical information should help you determine the cause of a heating failure in the dishwasher. Most models of these dishwashers have a heater detection fault that will cause the clean light to blink if the water is not heating properly. Running the diagnostic cycle usually clears this fault and resets the control.
If you need more help, resubmit your question with additional details.