no activity to upstream o2?

Neon_Frk · Post by **Neon_Frk** » Tue Apr 21, 2009 3:19 pm

ok like couple weeks ago i bought a new mp pcm. my cel went out for couple hours. well as i go home it comes back on and its a code 21. well i think its just a bad o2 so i buy a new one last friday. and i get the codes ran again and its a 21. any way i have no activity in my o2 sensor. i have went thru the whole harness for my o2 and i fix all of the bare wires and unhooked wires. my back o2 isnt hooked up either. and egr is blocked off too,. has anyone had this prob? im confuse on what to do? my gas mileage isnt that back i can go around 300-350 on a tank of gas depeding on how i drive. thanks James

spat12 · Post by **spat12** » Tue Apr 21, 2009 6:15 pm

If your downstream o2 is unplugged it will def throw a code. The 95 MPP PCMs were the only ones to disregard the Downstream o2. If you replaced the upstream already, and it still throws a code, chances are its ds related.

Neon_Frk · Post by **Neon_Frk** » Wed Apr 22, 2009 2:36 pm

well the upstream has no activity in the o2 tho. i might have to just live with the cel on.

spat12 · Post by **spat12** » Wed Apr 22, 2009 4:03 pm

How are you certain its the Upstream 02 that isnt responding? Did you scan it with an actual scan tool , like form AutoZone or something? And also, did it throw the same code when you had your stock PCM installed?

sabu · Post by **sabu** » Thu Apr 23, 2009 1:11 am

If you can do a live data scan and find out where your A/F ratio is then you can rule out if the upstream is actually working or not. Maybe you just received a dead sensor. Mass produced like everything else and shipped in huge trucks. Never know. Get it exchanged where you bought it if there is no voltage out of it. BTW can you get a P0XXX code out of it instead of just the idiot light 21 code? There will be separate codes for heater circuit and voltage circuit. If both codes show I would bet on dead sensor.

Neon_Frk · Post by **Neon_Frk** » Thu Apr 23, 2009 8:13 pm

ok ill do that get the po code. thanks