i got 0902 and 0901 and maybe 1001 but i could be wrong on the last one because i did not see it any where. 0901 is O2 sensor( right bank) and 0902 is downstream O2 sensor. could have them backwards though. i just replaced the bank one sensor today. it cost me $145. those things are really expensive. do i really need the downstream O2 sensor or should i buy a new one and replace it? also when i turned the screw to get the codes i started stripping the plastic screw. on other pictures i have seen metal screws. Is there any way for me to replace the plastic one with the metal one? I am not going to be able to turn the screw after awhile because it will be stripped all the way. Please help me. thank you

 

Diagnostic Trouble Code 0901 points to a problem with the
Front Heated Oxygen Sensor Heater on the right bank.

Diagnostic Trouble Code 1001 points to a problem with the
Front Heated Oxygen Sensor Heater on the left bank.

Diagnostic Trouble Code 0902 points to a problem with the
Rear Heated Oxygen Sensor Heater.

These three DTCs are alike. The malfunction is detected when the current in the Oxygen Sensor heater circuit is out of the normal range. The possible causes include the electrical harnesses, their connectors, or the Oxygen Sensor heaters themselves. You may test these heaters with an ohmmeter. This test is done with the engine off.

Follow the wires away from the Oxygen Sensor until you find the nearest electrical connector. Disconnect the connector. Viewed with the connector latch at the 12 o'clock position, there are three terminals. They are numbered 1-3, right to left. Be sure to measure the terminals in the connector half which is attached to the Oxygen Sensor, not the one which leads to the Engine Control Unit.

Measure the resistance between terminals 1 and 3.
The factory spec is 2.3-4.3 ohms at 77 degrees Fahrenheit.

Measure the resistance between terminals 1 and 2.
The reading should be infinity (no connection).

Measure the resistance between terminals 2 and 3.
The reading should be infinity (no connection).

It would be a remarkable coincidence for all three heaters to fail at the same time. Perhaps they are all powered through the same fuse. Check fuse #31 (15 amps) in the passenger cabin fuse block. That fuse block has three columns of fuses.
The left-most column contains fuses 1 - 11, numbered from bottom to top.
The middle column contains fuses 12 - 26, numbered from bottom to top.
The right-most column contains fuses 27 - 40, numbered from bottom to top.

The numbers are molded into the plastic fuse block. They are not easy to
read. A flashlight will be helpful.

 

Thank you very much Daniel. i will try and do what you said and post my results. i think i remember that you had a 99. is your screw on the computer plastic or is it metal? thanks again
Matt

 

I have a '99 GXE. I never had the Service Engine Soon light go on, so I never had the need to read the Diagnostic Trouble Codes. Therefore I don't know if that Engine Control Module mode selector screw is plastic. If yours is, I suppose mine is.