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Home >> Buick >> 2007 >> Allure CX >> Repair and Diagnosis >> External Pages >> Different car >> Section 71 (Engine Control System & Fuel System - 3.6L - DTC P2105 To DTC P2626) >> DTC P2122, P2123, P2127, P2128, or P2138 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, remove the fuse that supplies B+ to terminal X2-36 of the ECM.
  2. Disconnect the harness connector at the accelerator pedal assembly.
  3. Test for less than 5 ohms of resistance between the appropriate low reference circuit of the APP sensor and ground.
    • If greater than the specified range, test the low reference circuit of the APP sensor for a short to voltage, or an open/high resistance. If the circuit/connections test normal, replace the ECM.
  4. Install the fuse that supplies B+ to terminal X2-36 of the ECM.
  5. Ignition ON, test for 4.8-5.2 volts between the appropriate 5-volt reference circuit of the APP sensor and ground.
    • If less than the specified range, test the 5-volt reference circuit for a short to ground or an open. If the circuit/connections test normal, replace the ECM.
    • If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.
  6. Test the current output between each 5-volt reference circuit and ground. The current output should be greater than 80 mA for APP 1 and greater than 50 mA for APP 2.
    • If less than the specified range, test the appropriate 5-volt reference circuit for a high resistance. If the circuit/connections test normal, replace the ECM.
  7. Observe the appropriate APP sensor voltage parameter with a scan tool. Verify the voltage is less than 0.3 volts.
    • If greater than the specified range, test the signal circuit of the applicable APP sensor for a short to voltage. If the circuit/connections test normal, replace the ECM.
  8. Install a 3A fused jumper wire between the appropriate signal circuit and the 5-volt reference circuit of the APP sensor. Verify the APP sensor voltage parameter is greater than 4.8 volts.
    • If less than the specified range, test the appropriate signal circuit for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the ECM.
    • If both APP sensor voltage parameters display greater than 4.8 volts test the signal circuits of the APP sensors for a shorted together condition. If the circuit/connections test normal, replace the ECM.
  9. If all circuits/connections test normal, test or replace the accelerator pedal assembly.
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