lemon-mirror:
Home >> Pontiac >> 2006 >> Grand Prix Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - 3.8L - DTC P0446 To P2108 >> DTC P0685 >> Circuit/System Testing

Circuit/System Testing

  1. With the ignition OFF, remove the powertrain relay from the underhood fuse block.
  2. With the ignition ON, measure for battery positive voltage (B+) between the relay coil voltage supply circuit and ground.
    • If the voltage measures less than B+, repair the open or high resistance in the circuit to the relay coil. All wire circuit resistance should measure less than 2 ohms.
  3. Measure for voltage between the relay coil control circuit and ground.
    • If voltage is measured on the control circuit of the relay, test for a short to voltage.
  4. Connect a test lamp between the battery positive voltage supply circuit of the relay coil and the relay coil control circuit. Use a scan tool to command the powertrain relay ON and OFF. The test lamp should turn ON and OFF when toggling between the commanded states.
    • If the test lamp stays ON all the time, test for a short to ground on the relay coil control circuit or a faulty ECM.
    • If the test lamp stays OFF all the time, test for an open or high resistance on the relay coil control circuit or a faulty ECM. All wire circuit resistance should measure less than 2 ohms.
  5. Measure for B+ between the relay armature supply circuit, and ground.
    • If the voltage measures less than B+, repair the open or high resistance in the circuit to the relay armature. All wire circuit resistance should measure less than 2 ohms.
  6. With the ignition ON, test for voltage on each test point of the ETC fuse.
    • If voltage is present, test the ignition 1 voltage circuit between the ECM, the powertrain relay, and the ETC fuse for a short to voltage.
    • If both circuits test normal, replace the ECM.
  7. Connect a 20-amp fused jumper wire between the B+ terminal and the ignition 1 voltage terminal of the powertrain relay at the underhood fuse block. With a test lamp, probe both test points of the ETC fuse.
    • If the test lamp illuminates at both test points of the ETC fuse, repair the ignition 1 voltage circuit between the powertrain relay and the ECM for an open, high resistance, or a faulty ECM. All wire circuit resistance should measure less than 2 ohms.
    • If the test lamp only illuminates at one test point of the ETC fuse, repair the short to ground in the ignition 1 voltage circuit between the fuse and the applicable component. Replace the fuse, as necessary.
    • If the test lamp does not illuminate on either test point of the ETC fuse, repair the open or high resistance between the powertrain relay and the ETC fuse. All wire circuit resistance should measure 2 ohms or less.
  8. With a test lamp, test for voltage on both test points of the following fuses:
    • ETC Fuse
    • Emission 1 Fuse
    • If the test lamp fails to illuminate on one test point of each fuse, repair the open or high resistance between the fuse and the powertrain relay. All wire circuit resistance should measure 2 ohms or less.
· About lemon-mirror