Hey guys I've been owning my truck for about maybe 2 years and recently when I was driving my truck my check engine light came on I plugged it in to my obd scanner and I got the code 21 that says "front 02s signal" I already got under truck and looked at the plugs and cleaned them up and then unplugged my battery for about 2 hours and I started it back up and I still read the same code can anyone please help and to make it worse I have to smog it soon thanks guys

 

I hope you didn't pay more than $2 for a box of 100 OBD1 scanners. http://www.staples.com/Staples-reg-J...product_525923

Here's the procedure: http://web.archive.org/web/201211190...85diagnosi.pdf

Code 21 is: (1) Open or short in heater circuit of heated oxygen sensor for 0.5 sec. or more. (Tells you a LOT more than "front O2s signal," doesn't it?)

To test the sensor: http://web.archive.org/web/201003261...01heatedox.pdf

Remember that your code is for a problem in the CIRCUIT, not specifically to the sensor. Replacing the sensor is a good guess (except you don't have to guess, you can test). But you could have an open or short elsewhere. And unless you can see those teeny electrons, "looking" at the plugs (connectors?) can only get you so far.

 

Thank you ima go through all my wires I'm hoping maybe it got pinched somewhere

 

I was wondering about that as well