Mike's Workshop Manuals: Service manuals for every vehicle
Home >> Cadillac >> 2007 >> STS V >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls And Fuel - 4.4L - DTC P0153 To DTC P0690 >> DTC P0685 or P0690 >> Circuit/System Testing

Circuit/System Testing

  1. With the ignition OFF, remove the IGN 1 relay from the underhood fuse block.
  2. With the ignition ON, measure for battery positive voltage, B+, between the battery supply voltage coil 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 IGN 1 relay 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 supply voltage coil and the IGN 1 relay control circuit. Use a scan tool to command the IGN 1 relay ON and OFF using the Engine Controls Ignition Relay selection. 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 IGN 1 relay control circuit or a faulty ECM.
    • If the test lamp stays OFF all the time, test for an open or high resistance on the IGN 1 relay control circuit or a faulty ECM. All wire circuit resistance should measure less than 2 ohms.
  5. Measure for B+ between the relay battery supply voltage armature 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 ECT fuse.
    • If voltage is present, test the ignition 1 voltage circuit between the ECT fuse, the IGN 1 relay, and the ECT fuse for a short to voltage.
    • If both circuits test normal, replace the ECM.
  7. Connect a 20A fused jumper wire between the B+ terminal and the ignition 1 voltage terminal of the IGN 1 relay at the underhood fuse block. With a test lamp, probe both test points of the ECT fuse.
    • If the test lamp illuminates at both test points of the ECT fuse, repair the ignition 1 voltage circuit between the powertrain relay and the ECT 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 ECT 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 ECT fuse, repair the open or high resistance between the IGN 1 relay and the ECT fuse. All wire circuit resistance should measure 2 ohms or less.
scientia non olet · About Mike's Workshop Manuals