My stepdaughter just bought a 2000 300m. Check engine light came on and it is showing P1684-battery disconnect in last 50 starts. Also showing P0703-brake switch circuit malfunction. Anyone have any dealings with P0703? Her brake lights are working, but I noticed the cruise control does not work. The cruise light will come on, but you cannot set a speed. I am guessing they are related. I did a search here, but couldnt find anything on P0703.

Also noticed that the tachometer is not working. The needle appears to be all the way around and sitting under the needle stop. Everything else on the instrument panel works.

Thanks for any help and advice.

 

1684 common on these cars. Disconnect and clean the battery terminals AND the jump post connections, both + and- to cure that one.
P0703" Brake switch stuck" Note the brake switch has 3 sets of contacts, one is for the cruise. Try to reset the switch. Depress the brake and hold. Gently pull the plunger from the brake switch toward the pedal.
Once you release the brakes the switch will "self adjust" . If that does not work the switch may e failed

 

Well, as of last night, the light has went out. So we shall see if it returns.

 

Now she has informed me that the light is going on and off randomly.

 

Since the switch was only $10, I went ahead an replaced it. See what happens.

 

Just to update, replacing the brake switch solved the problem.