I have a 1995 T100 4x4 5VZFE (3.4 V6) with the check engine light on constantly. At times, the vehicle seems sluggish and the speedometer wavers and it usually has to shift to keep 55mph even on the slightest incline. As for checking the codes--my Haynes manual says that 1995 and newer have OBD-II (VECI type label, nor any other labels, say anything about OBD-II) and can't even check without scantool, but for the other models, it says to jump TE1 and E1 in the under hood diagnosis connector (which I have). I have tried different methods (Haynes manual is a little different than Autozone's manual), and the light just stays on steady without ever flashing. I have read GM OBD-I vehicles from the ALDL without problems, but I can't quite seem to figure out the Yota process. I tried checking when cold, after letting the truck warm up (just sitting until idle kicks down), and tried after I brought it back from about a 20 mile trip to the store. If anyone would be willing to point me in the right direction as to how to get the codes or even what might be wrong with the vehicle, I would greatly appreciate any help. Thank you.

 

Did you check and see if you had the OBDII connector? It should be located on the dash panel by the parking brake.

 

I have both connectors--hood and under dash. Would that mean OBD-II even though labels say nothing about it. Also, I went into the parts store and they said that they could not read (wouldn't even try) it because it used a different method.

 

Don't listen to the parts stores. If you have an obd2 port you have obd2. Plug a scanner into it and let us know which codes you get.

 

Checked it out today and found that it had set P0141-O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2). Now for a little research and figure out how to fix it...

 

Thats relatively common. If thats the only DTC, I can almost guarantee your O2 B1S2 is bad..