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Home › Cadillac › 1998 › Catera › Repair and Diagnosis › Engine Performance › System › Engine Control System - Tests W/Codes › Diagnostic Trouble Codes › DTC P0446 - EVAP Vent Valve Control › Diagnostic Procedures

Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  , then go to next step.
  2. Turn ignition on, with engine off. Using scan tool, command vent valve on and off. If vent valve turns on and off with each command, go to next step. If vent valve does not turn on and off with each command, go to step 5).
  3. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Jumper main relay control circuit to ground. Using DVOM on 10-amp scale, measure current between ground and valve control circuit at ECM harness connector for 2 minutes. If current draw is 0.1-0.75 amp, see DIAGNOSTIC AIDS. If current draw is not 0.1-0.75 amp, go to next step.
  4. Turn ignition off. Disconnect valve connector. Using DVOM, check resistance between ground and valve control circuit at ECM harness connector. If resistance is infinite, go to step 11). If resistance is not infinite, go to step 9).
  5. Turn ignition off. Disconnect valve connector. Connect test light between valve harness connector terminals. Turn ignition on. Using scan tool, command valve on and off. If test light turns on and off with each command, go to step 8). If test light does not turn on and off with each command, go to next step.
  6. With test light connected to ground, probe valve harness connector switched battery feed circuit. If test light is on, go to next step. If test light is off, go to step 10).
  7. Turn ignition off. Reconnect valve connector. Disconnect ECM harness connector located in engine compartment relay center. Jumper main relay control circuit to ground. Using a fused jumper wire connected to ground, probe valve control circuit at ECM harness connector. If valve operates, go to step 12). If valve does not operate, go to step 9).
  8. Check connections at valve. Repair as necessary. After repairs, go to step 14). If connections are okay, go to step 11).
  9. Repair valve control circuit. After repairs, go to step 14).
  10. Repair switched battery feed circuit to vent valve. After repairs, go to step 14).
  11. Replace vent valve. After replacing valve, go to step 14).
  12. Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 14). If connections and terminals are okay, go to next step.
  13. Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
  14. Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0446 is set, go to step 2). If DTC P0446 is not set, go to next step.
  15. If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.
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