OBD 2 and aftermarket alarm

2000 Tacoma 2.4 44,000 miles. After 20 years the check engine light came on. OBD does not communicate I have found that the vehicle has an aftermarket 'Viper' alarm which is probably causing the diagnostics to not work...any suggestions appreciated. The vehicle was purchased in August, the original owner has passed... Viper is not returning my emails. Thank you in advance !!

 

Never heard of an alarm causing issues with the OBDII. I'd check to make sure you don't have damaged pins in the connector, or some other issue.

I would just search for "OBDII won't communicate" or something like that.

 

there are 2 OBD connectors, the shop/factory one in the engine compartment and the generic OBDII port under the dash. The one under the dash receives its power from a 10 amp fuse labeled OBD (on board diagnostics) while the engine comparment one is powered from the PCM. There are 2 fuse panels on your Tacoma, one in the engine comparment and one under a panel by your left knee... I dont remember which panel the OBD fuse is locataed at.

 

Thank you !! Do you know where the underhood one is located ? The obd fuse is under the hood. It is good. My issue is either the installation of the car alarm or a mouse. I found a nest in the blower motor last fall. Looked as best as I could behind the glove box. The under dash one is getting power but will not connect with the tool. Tested the tool on another car and it works.

 

seems odd that it wont communicate, anyway, the under hood connector says "Diagnostics" and is a rectangular box and is for use with Toyota Service equipment, different connector than OBDII. I would verify the 2 ground wires on the generic OBDII port using the diagram then verify the white wire from the PCM to the OBDII connector for continuity... the PCM sits above the glove box. Hopefully your mouse friend didnt chew that wire. if all wires are good and you still cant communicate I would go to an O' Reillys auto parts or ? and see if their scan tool will connect. Not all scan tools are compatible with all makes/models even though they say they are.

 

Appreciate the info. I will keep digging.