Saab Trionic system regulates boost pressure by controlling a 2-coil, 3-way solenoid valve connected via hoses to turbocharger wastegate, compressor outlet and inlet. MAP sensor sends signal to ECM, which calculates correct boost pressure and sends signal to BPC valve, which controls the solenoid valve.
ECM pins 26 and 2 control the solenoid valve and send it power through circuit 54, via fuse 24. The control current is a pulse width modulated frequency at 90 Hz below 2500 rpm and 70 Hz above 2500 rpm. The change in frequency at 2500 rpm is to avoid resonance in the air hoses.
If pin 2 is grounded for longer than pin 26, boost pressure will drop. If pin 26 is grounded for longer than pin 2, the boost pressure will rise.
To regulate boost pressure, ECM first calculates the desired value based on programmed boost pressures for every engine speed and throttle position. Boost pressure for each engine speed is chosen so that desired torque curve is applied to the engine at wide open throttle. Specific limits are set for certain situations:
Basic boost pressure occurs when:
Removal & Installation
- Disconnect BPC valve wiring connector.
Disconnect BPC valve vacuum hoses.
NOTENote location of each hose to valve nipples.
- Remove BPC valve screws and remove valve.
Reverse removal procedure, reconnecting hoses to correct valve nipples.
BPC valve can be activated with an appropriate diagnostic scan tool.
- Check BPC valve resistance with the ignition OFF. Connect an ohmmeter across BPC valve-s two terminals. Resistance should be 2 to 4 ohms at 68°F (20°C).
- DTC 1549 will be set if intake pressure exceeds limits.
- Check for intermittent wiring faults with a voltmeter while wiggling wiring harness and connectors.
- Check fuse 24 and change it if necessary.