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Home >> Chevrolet >> 2021 >> Blazer RS, FWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 9 (Engine Controls And Fuel - 2.5L (LCV) - Diagnostic Information And Procedures (1 Of 2)) >> Diagnostic Information and Procedures >> DTC P0131, P0132, P0137, or P0138 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
  1. Ignition/Vehicle & All vehicle systems - Off
  2. Disconnect the appropriate electrical connector: B52 Heated Oxygen Sensor
  3. Ignition - On / Vehicle - In Service Mode & Engine - Off
  4. Test for 1.7 to 3.0 V between the test points: Signal circuit terminal 4 & Ground
    • If less than 1.7 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the appropriate electrical connector: K20 Engine Control Module
    3. Test for infinite resistance between the test points: Signal circuit terminal 4 & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    4. Test for less than 2 ohms between the test points: Signal circuit terminal 4 @ Component harness & The other end of the circuit @ Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: K20 Engine Control Module
    • If greater than 3.0 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the appropriate electrical connector: K20 Engine Control Module
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points: Signal circuit terminal 4 & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V - Replace the component: K20 Engine Control Module
    • Go to next step: If between 1.7 and 3 V 
  5. Verify the scan tool parameter: HO2S 1, 2 = 1.7 to 3.0 V
    • If less than 1.7 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the appropriate electrical connector: K20 Engine Control Module
    3. Test for infinite resistance between the test points: Signal circuit terminal 3 @ Component harness & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance - Replace the component: K20 Engine Control Module
    • Go to next step: If between 1.7 and 3.0 V 
  6. Connect a 3 A fused jumper wire between the test points: Signal circuit terminal 4 & Signal circuit terminal 3
  7. Verify the scan tool parameter: HO2S 1, 2 = 0.0 V
    • If greater than 0.0 V 
    1. Ignition/Vehicle - Off & Remove - Jumper wire(s)
    2. Disconnect the appropriate electrical connector: K20 Engine Control Module
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points: Signal circuit terminal 3 @ Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V
    5. Ignition/Vehicle - Off
    6. Test for less than 2 ohms between the test points: Signal circuit terminal 3 @ Component harness & The other end of the circuit @ Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: K20 Engine Control Module
    • Go to next step: If 0.0 V 
  8. Verify the following conditions do not exist:
    • B52 Heated Oxygen Sensor - Water intrusion @ Harness Connector
    • Evaporative Emission Canister - Saturated with fuel
    • Exhaust System - Leaking
    • Fuel - Contaminated/Poor Quality - Refer to: Alcohol/Contaminants-in-Fuel Diagnosis
    • Fuel Pressure - High/Low - Refer to: Fuel System Diagnosis
    • Vacuum leak @ Engine/Hoses / Lines
    • If a condition exists 

      Repair or replace as necessary

    • Go to next step: If no conditions exist 
  9. Test or replace the component: B52 Heated Oxygen Sensor
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