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Home >> Cadillac >> 2007 >> SRX 4.6 A, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Fuel System - 4.6L - DTC P0340 To DTC P2544 >> DTC P0685 or P0690 >> 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 battery supply voltage coil circuit terminal R52 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 terminal R53 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 terminal R52 and the powertrain relay control circuit terminal R53. Use a scan tool to command the powertrain 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 powertrain 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 powertrain 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 switch circuit terminal R54, 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 ECM 1 fuse.
    • If voltage is present, test the ignition 1 voltage circuit between the ECM 1, the powertrain relay, and the V8 ECM 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 R54 and the ignition 1 voltage terminal R51 of the powertrain relay at the underhood fuse block. With a test lamp, probe both test points of the ECM 1 fuse.
    • If the test lamp illuminates at both test points of the ECM 1 fuse, repair the ignition 1 voltage circuit between the ECM 1 fuse 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 ECM 1 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 1 fuse, repair the open or high resistance between the powertrain relay and the ECM 1 fuse. All wire circuit resistance should measure 2 ohms or less.
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