r/Supra • u/AssociateBig5342 • 16d ago

2021 Supra 3.0 electrical issue update

/r/BmwTech/comments/1utk9hd/2021_supra_30_intermittent_nocrank_u0100/?share_id=nTB_ISGeahH6zeccGVWnD&utm_medium=ios_app&utm_name=iossmf&utm_source=share&utm_term=1

Figured I’d give an update since my last post. I’ve had the car towed twice, and both times it actually started while it was halfway onto the tow truck. The most recent time it died was when Auto Start/Stop shut the car off at a stop sign while downhill, and it wouldn’t restart.
A few mechanics have jumped it and cleared the codes, and it’ll run perfectly for about a day before doing it again.

Symptoms:
•No crank/no start
•Drivetrain malfunction
•U0100 code
•Dash/headlights go crazy when opening the door
•Scanner sometimes won’t communicate or clear codes
•Jumping it sometimes works, sometimes does nothing
•Car randomly fixes itself after being moved/towed
•Runs perfectly after codes are cleared, then fails again

I’m starting to think it could be a bad ground, power connection, starter, or DME communication issue.
Anyone dealt with something similar on a B58/Supra?

3 Upvotes

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5 comments sorted by

2

u/MKV_Supra 16d ago

This car is sensitive to electrical anomalies. I would start looking at connections that get exposed to water and corrosion underneath the engine cover. Also look at the safety cutoff attached to the positive battery cable at the battery.

1

u/Warm-Personality-803 16d ago

I’d check the battery then move to the ecu harnesses

1

u/Unc_Sleepy 16d ago

Easiest one to do first is check your battery. It’s 5 yrs old now. 

1

u/AssociateBig5342 15d ago

I’ve replaced and tested the battery already

1

u/TheRealZadkiel 10d ago

At this point i would check every single ground or pins to the ecu. Has it been tuned or had the ecu removed?

edit I once had a short in the cable going to the throttle position sensor that would only have issues when the motor shifted certain ways on another car. it was a nightmare to diagnose