I have a 2013 Boss 302 and I’m experiencing an intermittent electric power steering issue.

The message that appears is “Power Steering Assist Fault”. When it happens, the steering becomes very heavy, as if the electric assist shuts off completely. The problem is intermittent and doesn’t happen every time I start the car.

Here are the details:

• Sometimes I start the car and everything works perfectly.
• Other times, shortly after the engine starts, I get the “Power Steering Assist Fault” message and the steering becomes very heavy.
• If I shut the car off and restart it, sometimes the problem disappears and the steering works normally again.
• At one point I disconnected the battery for a while, reconnected it, and the steering worked normally afterward.
• I drove the car for 20–30 minutes with no issues.
• On another occasion, I started the car in the morning and everything was fine. I shut it off, let it sit for about 30–40 minutes without driving it, then restarted it and immediately got the fault message again.
• The car originally had a fairly new Duralast Gold 96R battery installed.
• Charging voltage with the engine running is approximately 14.2 volts.
• I also tested the system by leaving the headlights on for a few minutes with the engine off, then starting the car. No fault appeared during that test.
• The 80A EPAS fuse was inspected, removed, and reinstalled.
• At one point the radio reset itself, which made me suspect a possible power, ground, or connection issue.
• There is no permanent steering wheel warning light illuminated; only the message appears in the information display.

To rule out the battery, I installed an Interstate non-AGM battery rated at 720 CCA and drove the car for about 3 days. Everything seemed fine initially, but on the third day the exact same “Power Steering Assist Fault” message returned and the steering became heavy again.

A mechanic scanned the car and told me that the “power steering is bad,” but he did not provide the actual trouble code.

At this point I’m trying to determine whether this sounds more like:

1. A failed EPAS steering rack.
2. A faulty steering torque sensor inside the rack.
3. A failing PSCM (Power Steering Control Module).
4. A wiring or connector issue at the rack.
5. A power supply or ground issue.

Has anyone with a 2011–2014 Mustang GT or Boss 302 experienced similar symptoms? Any input would be greatly appreciated.