I have a '97 Chevy Silverado 2wd, auto trans, 5.7, There are 3 codes that are showing up on diagnostic report, P0134 P0135 and P1133. Could you please help me with these codes

http://www.obd-codes.com

P0134 O2 sensor drivers side before catalytic converters.
PO141 O2sensor drivers side after converter
P1133 insufficient switching of O2 sensors. Will probably
go away once sensors are replaced.

You can look up the error codes on http://www.obd-codes.com.
Because the error codes indicate heater circuit failure.
P0135 and P0155 mean the heater circuits for the front oxygen sensors are not working properly. You need to check the fuse.
#15 under the hood I think.
If that is OK, make sure the exhaust system is grounded. I believe the ground strap is on the back of the cylinder head - right side.

It would be rare that both O2 sensors died again, that quickly. I suspect the dealer didn't really do any diagnostics and just replaced parts (cheap option at least for them).

with those codes showing, it could be either bad O2 sensors or there is a problem with the wiring to those sensors. Also, the wrong sensors may be installed. I'm assuming codes P0134, P0135, P0155.

For others viewing this:

P0134 = O2 sensor circuit-no activity detected (bank 1 sensor 1)

P0135 = O2 sensor heater circuit malfunction (bank 1 sensor 1)

P0155 = O2 sensor heater circuit malfunction (bank 2 sensor 1)

First, I wouldn't let that guy work on your car. P1133 is "O2 Sensor Slow Response - Sensor 1" Anybody that has been in the auto repair business for more than a week should know that Sensor 1 is ALLWAYS the FRONT sensor.

Note: O2 sensor codes do not necessarily mean that an O2 sensor needs to be replaced. Most O2 Sensor codes are caused by something other than the O2 Sensor itself. (there are several different possible O2 Sensor codes for your car. P0131, P0132, P0133, P0134, P0138, P0171, P0172, P1133, P1134)

The most likely cause of DTC (Diagnostic TroubleCode) P1133 is contamination of the O2 Sensor. Replacing a contaminated O2 Sensor without repairing the source of the contamination will only result in a repeat repair. It could be caused by bad fuel, improper use of RTV sealant, engine oil or engine coolant. I have seen this caused many times by engine oil leaks that run down the exhaust and clog the holes in the side of the sensor shield. (The sensor must "breathe" to work properly)

Then on the other hand, if your vehicle has a lot of miles on it, the sensor could be just chemically worn out. In any case, the FRONT sensor is the one that is setting the code.

I found the codes on a site for the EX model.

Indicates to me that the O2 sensor is in need of replacement.

P0134 O2 Sensor Circuit No Activity Detected - Bank 1 Sensor 1
P0135 O2 Sensor Heater Circuit - Bank 1 Sensor 1

Yes. In all likelyhood replacing the one sensor should fix it although there are a few other potential causes to be aware of. More info - P0134 - P0135

Code P0134 is the #1 oxygen sensor on bank 1, up near exhaust manifold.
Code P1133 is insufficient switching of bank 1 02 sensor. Need to replace it.

P1133 - Heated Oxygen Sensor (HO2S) Insufficient Switching Bank 1 Sensor
You will need to check the output signal from this O2 sensor, if the voltage low (.10-.25 volts) try spraying propane into the air cleaner to see if the O2 volts go up, it should go to around .75 volts, if nothing happens then the O2 sensor is bad, bank #1 O2 is on the same side as #1 cylinder
PLEASE RATE THIS INFO.

P0130--O2s sensor circuit 1
P0134--O2s circuit insuffient Act sensor 1
P0135--H02s heater performance sensor 1