Need Schematic -- Heated O2 Sensor 1.. [Archive] - Forum


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07-06-2007, 07:03 PM
Anyone have a schematic for the heated o2 sensor (pre-cat one that's on the rear manifold)??

Have a P0135 keeps coming back, scan tool showing no current to this thing. New O2 sensor too. thks in advance

07-07-2007, 11:36 PM
I have the schematic, the sensor gets its heater voltage from the ERLS fuse, fuse #47.. wasn't it for me, on to the rest of the troubleshooting chart..

07-08-2007, 02:16 AM
Here you go.

07-08-2007, 02:17 AM
Thanks for attachin that Scott... is exactly what I have. I don't have access to gm service site any more had to hit up Ryan :(

07-08-2007, 02:20 AM
No access to a Tech 2 either? Only way I know to test 'em is to put a test light in-line with the heater + and low ref circuits at the O2 connector and see if you get 12V. AFAIK you have to command the heater on if the O2 is unplugged for this to work.

07-08-2007, 02:44 AM
Have access to a tech 2.. I have the gm service manual page just didn't have the schematic come through -- going to run through the checklist tomorrow. What you said is my next step... I have to figure out if the supply is no good or if the return to the PCM is the part at fault. Will keep ya updated

07-08-2007, 11:01 AM
OMG this just solved my P0133 problem, #47 was blown

07-08-2007, 03:08 PM
I hate you

07-08-2007, 04:58 PM
seth, I have a Ryobi stud sensor if you want to use that this coming weekend.

07-08-2007, 06:45 PM
Check the threading on the manifold and the sensor, make sure they are clean, IIRC the threads are what grounds the O2.

07-08-2007, 06:47 PM
^ That's only in old-school one-wire O2 sensors. These newer O2s actually have a feed and return circuit for both the heater and the sensor signal as to avoid interference from a dirty ground.

07-08-2007, 07:17 PM
Yeeeup... reference goes back to the PCM. I'm working and won't have a chance to look at this til Tues. Worse comes to worse gonna rig up some stuff ;)

11-24-2007, 02:09 PM
Meh, so I am all kinds of lazy and finally got to looking through this.

Ran through the service manual steps for diagnosing the problem... wirng is good from the PCM connector all the way to the O2 sensor plug for the heater control/reference circuit (black/white wire). The Brown wire, which is +12v IGN, is good as well when the car is in ON. So, I am pretty stumped. My scan tool is showing the PCM commanding the circuit on, but there is just no current going out that black/white wire. So I guess at this point looks like an ew PCM :(

11-24-2007, 04:47 PM
Doesn't the GM service manual advise to set the car on fire with GM tool part# OM3827655-85?