97 O2 Heater fault


lordkyleofearth

15+ Year Member

Joined
Jan 7, 2010
Messages
53
Points
3,101
City
Boerne, Tx
Vehicle Year
97/95 hybrid
Transmission
Manual
Hey everyone.

I recently bought a 97 ranger 2.3 and have just finished rebuilding/installing the motor. All is working well except I keep getting a Bank 1 O2 heater circuit fault code. I traced the wiring down and had continuity between the upper and lower sensors on one wire, continuity to PCM (pin 93) on the downstream sensor, and no continuity from the upstream to PCM (pin 95). I ran a new wire to make that connection and still am getting the code.

The 13mpg super-rich conditions I am currently having are no fun. Any ideas on what is going on? Did I run the wiring incorrectly?

Thanks,
Kyle
 
bad sensor? did you just do continuity or did you do voltage drop? VD is much more accurate.
 
Continuity test only. Both O2 sensors are new (Advance Auto, Bosch generic) and the heater fuse is new as well.
 
hmm, are you sure you wired them up right?
 
Are you sure its not a code for the downstream (after the cat) sensor?
 
The code is P0135.

One sensor was prewired, the other was the one that you wire in yourself. I followed the directions and the double checked myself prior to install.

Since they are on a common circuit, I suspect the fault could be with either sensor or any of the wiring, right?
 
I think I am going to chase the wiring again tomorrow. To be clear:

I should have continuity (with the sensors installed and wired correctly) between pins 93 and 95 on the PCM correct?

Sensors removed, the harness should give continuity from #95 to the upper sensor (arbitrarily, wire A). Upper sensor to the lower sensor (wire B) and then lower sensor to PCM #93 (wire C). One of the wires (A or C) will have a quick detour to the fuse box. Right?

And if I see no continuity with the sensors installed, but I do have continuity along each leg (sensors removed) then I can conclude that the generic sensor is wired wring. Does that sound correct?
 
sounds right. Don't have a diagram in front of me, but that sounds about right.
 
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