Bad C/OPN relay?

Hey guys! I was wondering if you could help with any suggestions. My Dad has a 2000 Tundra 4.7 crew cab. He jumped in the truck to take off and the truck would not start. We looked under the hood and heard a clicking noise. Opened the relay/fuse box and realized the C/OPN relay was firing every 5-8 seconds or so. Also something under the 4.7 plate was firing at the same time as the relay. Together this killed the battery. It almost sounded like a blinker was on, or the four ways, but that was not it. When the driver side door opened it became intermittent and or stopped. Any ideas on what would fire the relay switch suddenly and for no apparent reason? I will replace the switch tomorrow when the stores open... Thanks for the advice

 

Thanks for the welcome! Yea, no luck on any codes. The check engine light did not come on. I gave him a jump, and when he came back, listened for the clicking and it was gone. As near as we can tell at this point, it was the car alarm firing off. But there was no sound or flashing lights so we are not sure. The alarm fob was lost long ago. Not quite sure what happened, but it seems to have worked itself out. My 91 Ford F-150 was self- healing, so maybe the Toyota is too. I will repost if the problem comes back....Thanks.

 

If the voltage drops low enough vehicles sometimes freak out when it comes to relays and computers. Likely what happened here

 

Yeah if the battery gets low the alarm can trigger. Sometimes the alarm will not allow the vehicle to start when it is going off.