Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Power Sustain Relay (PSR)
The PSR is wired in parallel with the electronic engine control (EEC) power relay. The PCM and the TCM use the PSR to keep the modules powered. The PCM and TCM must be powered to complete the normal power down sequence, after the key is turned to the OFF or ACCS position. For additional information on normal power down sequence, refer to HYBRID ELECTRIC CONTROL SOFTWARE . When the 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 condition. The PSR circuit short to ground condition keeps the modules powered at all times and it may cause an excessive key off load on the low voltage system.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.