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Home >> Saab >> 1997 >> 9000 CS, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics - TRIONIC Fuel Control System >> Circuit Tests >> DTC P1549: Boost Pressure Control Valve (APC Valve) >> Diagnosis & Repair Procedure

Diagnosis & Repair Procedure

  1. Check for other DTCs. If DTCs P0105-P0108 are present, perform diagnosis for these DTCs first. If DTCs P0105-P0108 are not present, go to next step.
  2. Disconnect air hoses marked "W" and "C" from boost pressure control valve. Connect hoses together. Test drive vehicle. If only basic boost pressure is obtained when driving at WOT from low engine RPM, and when opening throttle suddenly at higher engine RPM, go to next step. If other than basic boost pressure is obtained under the same conditions, check for a binding wastegate, defective diaphragm unit, defective or incorrectly connected control hoses, or incorrectly adjusted basic boost pressure.
  3. Check fuse No. 24. If fuse is okay, go to next step. If fuse is blown, replace fuse. Go to step 8).
  4. Check 3 air hoses on boost pressure control valve. Ensure hoses are in good condition and correctly installed. Repair as necessary, then go to next step. If hoses are okay, go to next step.
  5. Disconnect boost pressure control valve connector. Turn ignition on. Connect test light between connector terminal No. 2 and ground. See Figure . If test light comes on, go to next step. If test light does not come on, repair wiring between connector terminal No. 2 and fuse No. 5. Go to step 8).
  6. Connect ohmmeter between valve terminals No. 1 and 2, and between terminals No. 2 and 3. If resistance is 2-4 ohms, go to next step. If resistance is not 2-4 ohms, replace boost pressure control valve. Go to step 8). Turn ignition on. Reconnect boost pressure control valve connector. If a weak buzzing sound is heard, go to next step. If a weak buzzing sound is not heard, check wiring between valve connector terminal No. 3 and ECM terminal No. 2.
  7. Turn ignition on. Ensure boost pressure control valve connector is connected. Using scan tool, select ACTIVATE, then BOOST PRESS VALVE. If a loud buzzing sound is heard, replace boost pressure valve. Go to next step. If a loud buzzing sound is not heard, check wiring between boost pressure control valve connector terminal No. 1 and ECM terminal No. 26. Go to next step.
  8. Clear DTCs. Start and warm up engine until it reaches normal operating temperature. Accelerate at WOT from 1500 RPM to at least 3000 RPM 6 times. Check if DTC reoccurs and whether pressure switch opens during driving cycle. If DTC reoccurs, replace ECM.
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