Blazer Forum - Chevy Blazer Forums - oxygen sensor trouble codes and "fuel trim" code, i just got new o2 sensors....

What are you driving?

P0131 - HO2S Circuit Low Voltage Bank 1 Sensor 1
P0137 - HO2S Circuit Low Voltage Bank 1 Sensor 2
P0151 - HO2S Circuit Low Voltage Bank 2 Sensor 1
P0171 - Fuel Trim System Lean Bank 1

Start with the trouble shooting steps in the links above. See where that takes you.

*EDIT* - Here is the description for P0137. I do not have it in my other reference though.

Quote:

DTC P0137 - HO2S CIRCUIT LOW VOLTAGE BANK 1, SENSOR 2

Circuit Description

VCM provides about 0.45 volt reference to Heated Oxygen Sensor (HO2S). HO2S sensor signal voltage varies from about one volt when exhaust is rich to about 0.1 volt when exhaust is lean. VCM reads and stores sensor voltage information and evaluates the voltage samples to determine amount of time sensor voltage is out of range. If HO2S voltage is out of predetermined range, DTC will set.

Conditions required to test for DTC are:

No ECT, IAT, MAF, MAP or TP sensor DTCs set.
No EVAP system DTC set.
No other DTC tests in progress.
No device control active.
System voltage measures at least 9 volts.

Diagnostic Procedures

Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING - 4.3L article. Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
Start engine and allow it to reach operating temperature. Place gear selector in Park or Neutral, and apply parking brake. Increase engine speed to 1200 RPM. Using scan tool, read HO2S BANK 2, SENSOR 1 voltage. If voltage is less than 0.086 volt, go to next step. If voltage is not less than 0.086 volt, go to step 4).
Turn ignition off. Disconnect HO2S connector. Connect a jumper wire between HO2S harness connector ground circuit and chassis ground. Turn ignition on, engine off. If voltage is 0.35-0.55 volt, go to step 7). If voltage is not as specified, go to step 5).
DTC P0137 is intermittent. If any additional DTCs are set, diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
Check HO2S sensor harness connector signal circuit for short to ground. If short is found, go to next step. If circuit is okay, go to step 8).
Repair circuit as necessary. After repairs, go to step 9).
See DIAGNOSTIC AIDS.
Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter DTC P0137. Operate vehicle within conditions required to set DTC. If scan tool displays RAN AND PASSED, go to next step. If scan tool does not display RAN AND PASSED, return to step 2).
Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Diagnostic Aids

Using scan tool, observe LT FUEL TRIM values at different RPM. If conditions to set DTC P0137 exist, value should be about 158 or greater. Check for an intermittent short to ground in HO2S signal circuit. Never solder HO2S wires. Check for fuel contamination. Check for proper fuel pressure. Check for exhaust leaks.