GM'* O2 sensors are made by Denso and Bosch. Maybe they are built in China that Im not sure. In my experience with engineering and TAC I have never heard or replacing a 2nd sensor due to a faulty sensor. If you have a bulletin or a P.I. i may not know about I would be interested in seeing it. Sorry if my statement seemed to upset you that was not my intention and I do apologize.

took my truck to a chevy dealer today and they put it on their computer - yep code p1133 - same as others. they told me there was a bulletin on it because of the change in the gas over the past few years the computer needed to be reprogramed. when i asked if that meant the o2 sensors didn't need to be replaced in the first place they just smilled and said have a nice day. the shop i took it to that replaced the sensors in the first place have certified mechanics and they told me that they pay GM for all the updates and bulletins so if that is the case, what was it not shared with them. basically i'm out the 450 for the sensors - the 135 for the new battery and all it would have cost me was the 114 for the computer check at the dealer. sounds like something is not on the up and up.

guess i will have to wait and see if the check engine light comes back on or if they really got it fixed. i will let you know one way or the other. Thanks to everyone for your help and guidance.

thanks for the update. prices like that is why i work on cars myself

just an up date my truck still will not pass em inspection. it said the evaporative system is not complete and the oxygen sensor is not complete. they said i need to drive it some more. you would think after 100 miles everything would have reset and be ready. guess not, or at least not in my case. will try for the em inspection again tomorrow. called dealer and asked them - no help at all - just drive more and keep trying. i asked the guy if by friday - which i figured would be over 300 miles - it still doesn't pass them what - again no help. i told him they were suppose to be the experts on gm products he should be able to tell me something but....... if anyone is interested in the "bulletin" they said was out there on this problem i have what i think is a number so just let me know.

I'm not sure what "not complete" means. With mine it was "not ready". It just means that it hasn't been through enough cold start cycles. Number of miles driven is probably not relevent. It took mine about a week to finaly get there. As long as you're not getting a light it is probably ok. Give it a few more days of cold start driving cycles and then let them check it.

Don is correct. It'* not the miles driven, it'* the number of drive cycles.

The criteria for EVAP system to run its tests can take a few drive cycles. Parker2129 and 2Kg4u are right. Cold start conditions must be met and certain driving conditions must also be met to run the tests. There is a Inspection/Maintenance Complete System Set Procedure that a dealer can run BUT you need to reviewing TECH 2 data. Just drive it a few more days and try again. Lets us know how you make out. I would "THINK" that after 100 miles P1133 should have run its test.

ok about p1133...
read this link to a page in this forum- https://www.gmforum.com/obd-ii-troub.../p1133-284141/

changing the battery definately didnt help this problem. Like the other posters here i think it could be 02 heater circuit, ref/signal wire problem. Though if it were a wiring problem i think you would get a voltage high or low/ circuit open code. Id definately get a scanner look at live data and see how that 02 sensor is acting. In closed loop at an idle most upstream 02 sensors switch back and fourth in a range of 200-800 mv. Also watch fuel trim. If ltft and stft combined it is more than +10 on that side u may have an exhaust leak causing the 02 sensor to detect a lean condition. I got a feeling its a bad 02 sensor. I know you said they changed it maybe its bad right of the shelf.

ABout your computer not being ready. Again like others have said criteria has to be met in order to initiate the drive cycle monitors. I found these instructions initiate all monitors on a another gm forum. good luck

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A complete driving cycle should perform diagnostics on all systems. A complete driving cycle can be done in under fifteen minutes.

To perform an OBDII Driving cycle do the following:
Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50°C (122°F) and within 6°C (11°F) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.

Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.

Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.

Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.

Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.

Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.

Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.
Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.

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There is no drive trace as a whole, however, some monitor cycles are similar and may pass through simultaneously

Catalyst moniotor:

Pre-req: no codes present, IAT above 32 deg f; ECT is above 167 deg f; mass air flow greater than 15 gm/*, engine load is below 63% and steady, engine speed is below 3000 rpm

-Idle vehicle 5 minutes until it is in closed loop

-drive 5 min at steady speed above 50 mph

-drive 2 min at steady 40 mph

-drive 2 min at steady 50 mph

EGR Monitor:

Pre-req: no codes present, ECT is avove 75 deg f; barometric pressure above 72kPa

1. Idle vehicle 5 minutes until it is in closed loop

2. Accelerate and drive for 1 min at steady speed above 50 mph

3. coast vehicle down to 20 mph (vehicle in drive or w/ clutch engaged, brake off)

4. repeat steps 2 and 3 four times

* the GM egr runs during the deceleration portion of the drive trace

Evaporative Monitor:

Pre-req: no codes present

-drive 5 min at steady speed between 30 and 60 mph

-stop and idle 2 min

O2 Sensor Monitor:

Pre-req: no codes present, IAT above 32 deg f; ECT is avove 167 deg f

-Idle vehicle 5 minutes until it is in closed loop

-drive 3 min at steady speed above 50 mph

-drive 2 min at steady 40 mph

-drive 2 min at steady 50 mph