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Home >> Chevrolet >> 2021 >> Blazer RS, FWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 11 (Engine Controls And Fuel - 2.5L (LCV) - Diagnostic Information And Procedures (2 Of 2)) >> Diagnostic Information and Procedures >> DTC P2122, P2123, P2127, P2128, or P2138 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
    NOTE:

    It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Disconnect the electrical connector: B107 Accelerator Pedal Position Sensor
  3. Test for less than 5 ohms between the test points:
    • {APP Sensor 1} Low Reference circuit terminal 4 & Ground
    • {APP Sensor 2} Low Reference circuit terminal 5 & Ground
    • If 5 ohms or greater 
    1. Disconnect the electrical connector: K20 Engine Control Module
    2. Test for less than 2 ohms between the test points:
      • {APP Sensor 1} Low Reference circuit terminal 4 @ Component harness & The other end of the circuit @ Control module harness
      • {APP Sensor 2} Low Reference circuit terminal 5 @ 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 less than 5 ohms 
  4. Ignition - On / Vehicle - In Service Mode
  5. Test for 4.8 to 5.2 V between the test points:
    • {APP Sensor 1} 5 V Reference circuit terminal 2 & Low Reference circuit terminal 4
    • {APP Sensor 2} 5 V Reference circuit terminal 1 & Low Reference circuit terminal 5
    • If less than 4.8 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: K20 Engine Control Module
    3. Test for infinite resistance between the test points:
      • 5 V Reference circuit terminal 2 @ Component harness & Ground
      • 5 V Reference circuit terminal 1 @ Component harness & 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:
      • 5 V Reference circuit terminal 2 @ Component harness & The other end of the circuit @ Control module harness
      • 5 V Reference circuit terminal 1 @ 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 5.2 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: K20 Engine Control Module
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points:
      • 5 V Reference circuit terminal 2 @ Component harness & Ground
      • 5 V Reference circuit terminal 1 @ Component harness & 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 4.8 and 5.2 V 
  6. Verify the scan tool parameter:
    • APP Sensor 1 = Less than 0.3 V
    • APP Sensor 2 = Less than 0.3 V
    • If 0.3 V or greater 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: K20 Engine Control Module
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points:
      • {APP Sensor 1} Signal circuit terminal 3 @ Component harness & Ground
      • {APP Sensor 2} Signal circuit terminal 6 @ Component harness & 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 less than 0.3 V 
  7. Connect a 3 A fused jumper wire between the test points:
    • {APP Sensor 1} Signal circuit terminal 3 & 5 V Reference circuit terminal 2
    • {APP Sensor 2} Signal circuit terminal 6 & 5 V Reference circuit terminal 1
  8. Verify the scan tool parameter: = Greater than 4.8 V
    • If 4.8 V or less 
    1. Ignition/Vehicle - Off & Remove - Jumper wire(s)
    2. Disconnect the electrical connector: K20 Engine Control Module
    3. Test for infinite resistance between the test points:
      • {APP Sensor 1} Signal circuit terminal 3 @ Component harness & Ground
      • {APP Sensor 2} Signal circuit terminal 6 @ Component harness & 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:
      • {APP Sensor 1} Signal circuit terminal 3 @ Component harness & The other end of the circuit @ Control module harness
      • {APP Sensor 2} Signal circuit terminal 6 @ 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 greater than 4.8 V 
  9. Test or replace the component: B107 Accelerator Pedal Position Sensor
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