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HOMESERVICE MANUALSCHEVROLET2001CHEVY EXPRESS G3500, VAN PASSENGER EXTENDED, 6.5 FREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 56 (ENGINE CONTROLS SELF-DIAGNOSTICS - 2.2L CNG)DIAGNOSTIC TESTSDTC P0134: O2S1 CIRCUIT - INSUFFICIENT ACTIVITYDIAGNOSTIC PROCEDURES
2001 Chevrolet Chevy Express G3500, Van Passenger Extended, 6.5 F

Diagnostic Procedures

2001 Chevrolet Chevy Express G3500, Van Passenger Extended, 6.5 FSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2002 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
  2. Using scan tool, establish communication with the AF ECM. Capture the DTC Information from the AF ECM into the scan tool. Clear the DTC Information using a scan tool. Reset the Fuel Trim values. Start and idle the engine until normal operating temperature is reached. Using scan tool, monitor the O2S voltage for the sensor that applies to this DTC. Is the O2S voltage fixed within 0.00-1.0 volt? If yes, go to step  5 . If no, go to next step.
  3. The condition that set this DTC is not present. This DTC may have been set by one of the following conditions: O2S connector water intrusion, an intermittently open O2S High signal circuit, an intermittently open O2S Low circuit, an O2S Low circuit with high resistance to ground, AF ECM ground circuits with high resistance to ground, poor O2S or control module connector terminal contact, an exhaust system leak (typically within 12 inches (30.5 cm) upstream of the O2S) or a defective O2S. Repair any of the conditions as necessary. Was a condition found and repaired? If yes, go to step  16 . If no, go to next step.
  4. The fault is not present. See DIAGNOSTIC AIDS  . Are any DTCs stored that have not been diagnosed? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, refer to INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  5. Start engine and allow to idle until normal operating temperature is reached. Using scan tool, communicate with AF ECM. Using scan tool, select special functions and force a switch over to gasoline. Communicate with PCM. Verify engine is operating in closed loop fuel control. Monitor suspect O2S voltage. If O2S voltage is fixed between zero and one volt, go to next step. If O2S voltage is not fixed between zero and one volt, go to step  11 .
  6. Turn ignition off. Disconnect the O2S connector for the sensor that applies to this DTC. Jumper the O2S High signal circuit directly to the negative battery terminal. Turn ignition on, with engine off. Using scan tool, monitor the O2S voltage for the sensor that applies to this DTC. Is the O2S voltage less than 20 mV? If yes, go to step  10 . If no, go to next step.
  7. Turn ignition off. Remove the jumper from the O2S terminal. Disconnect the Powertrain Control Module (PCM) connector containing the O2S High and Low circuits. Using the J-39200 Digital Multimeter (DMM) measure the resistance of the O2S High signal circuit between the control module connector terminal and the O2S harness connector terminal. Measure the resistance of the O2S Low circuit between the Low circuit terminal and a PCM ground circuit terminal at the PCM connector. Is the individual resistance of both circuits less than 5 ohms? If yes, go to next step. If no, go step  9 .
  8. Check for poor connections at PCM. Repair as necessary. Was a terminal repair made? If yes, go to step  16 . If no, go to step  15 .
  9. Repair the circuit that measured high resistance. After repairs, go to step  16 .
  10. Check for exhaust leaks about 12" upstream of O2S. Repair as necessary. Was an exhaust system repair made? If yes, go to step  16 . If no, go to step  13 .
  11. Inspect the oxygen sensor signal and low circuit for continuity between the AF ECM connector terminals and the oxygen sensor connector terminals. Inspect these circuits for shorts to other circuits or to ground. Ensure the oxygen sensor, PCM and the AF ECM connectors are disconnected before testing circuits. Repair wiring as necessary. Was a wire repair made? If yes, go to step  16 . If no, go to next step.
  12. Replace AF ECM. See ALTERNATE FUEL ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) AF ECM with correct vehicle software and calibration. See ALTERNATE FUEL ENGINE CONTROL MODULE  under PROGRAMMING. After performing repairs and procedures, go to step  16 .
  13. Perform fuel system diagnosis then return to this test step. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS (CAVALIER CNG) in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article. If fuel system problem is found and repaired, go to step  15 . If fuel system problem is not found and repaired, go to next step.
  14. Replace O2S. After repairs, go to step  16 .
  15. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article. Program (flash) PCM with correct vehicle software and calibration. See POWERTRAIN CONTROL MODULE REPROGRAMMING  under PROGRAMMING. To perform CKP variation learn procedure, a switchover to gasoline operation is necessary. Remove CNG fuse (20-amp) located in underhood fuse block to perform switchover. Perform CKP system variation learn procedure. See CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE  under PROGRAMMING. After performing repairs and procedures, go to next step.
  16. Reconnect all disconnected or removed components, connectors, fuses, etc. Using scan tool, clear all DTC Information from BOTH the Powertrain Control Module (PCM) and the AF ECM. Using scan tool, communicate with BOTH the PCM and the AF ECM in order to reset the Fuel Trim values to zero. Start engine. Operate the vehicle within the Conditions for Running this DTC until the scan tool indicates the diagnostic ran. See CONDITIONS FOR RUNNING DTC  . Does the scan tool indicate the DTC passed? If yes, system is okay. If no, go to step  2 .
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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.