Power Sustain Relay (PSR)

The PSR is wired in parallel with the electronic engine control (EEC) power relay. The PCM and transaxle control module (TCM) use the power sustain relay to keep the modules powered. The PCM and TCM must be powered to complete the normal power down sequence, after key is turned to OFF or ACCS position. For more information on normal power down sequence, refer to NORMAL POWER DOWN SEQUENCE . When the ignition key is cycled from the OFF to ON or the ON/START position, the PCM smart driver grounds the PSR circuit. The PSR coil is energized and it closes the contacts of the PSR supplying the modules with the B+ power. The PSR coil stays energized after the key is turned to the OFF or the ACCS position until normal power down sequence is successfully completed. The PCM monitors the PSR output for an open and short circuit fault condition. The PSR circuit shorted to ground fault condition keeps the modules powered at all times and it may cause an excessive key off load on the low voltage system.