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Home › Cadillac › 2009 › DTS 4.6 9 › Repair and Diagnosis › Engine Performance › System › Engine Control System & Fuel System - 4.6L - DTC P0340 To DTC P2433 › DTC P0685 or P0690 › Circuit/System Testing

Circuit/System Testing

  1. With the ignition OFF, remove the powertrain relay from the underhood fuse block using the J 43244  . See Special Tools .
  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 powertrain 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 powertrain relay control circuit. Use a scan tool to command the powertrain relay ON and OFF using 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 powertrain relay control circuit. If the circuit tests normal, replace the control module.
    • If the test lamp stays OFF all the time, test for an open or high resistance on the powertrain relay control circuit. If the circuit tests normal, replace the control module. 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 CRNK fuse.
    • If voltage is present, test the ignition 1 voltage circuit between the ECM/CRNK, the powertrain relay, and the ECM/CRNK 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 powertrain relay at the underhood fuse block. With a test lamp, probe both test points of the ECM/CRNK fuse.
    • If the test lamp illuminates at both test points of the ECM/CRNK fuse, repair the ignition 1 voltage circuit between the powertrain relay and the ECM/CRNK for an open or high resistance. If the circuit tests normal, replace the control module. All wire circuit resistance should measure less than 2 ohms.
    • If the test lamp only illuminates at one test point of the ECM/CRNK 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 ECM/CRNK fuse, repair the open or high resistance between the powertrain relay and the ECM/CRNK fuse. All wire circuit resistance should measure 2 ohms or less.
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