P0700 and U0100

[Spacepeanut34]

I was driving down the highway I was going 65mph at the time I stepped on the gas got up to 75mph my rpm sat at 6.5 and my car started to sound like a vacuum I let off the Gaston a split second then stepped on it again I had no reaction I pulled over to the should and tried to start my car and but it would only crank it wouldn’t turn over I got it towed back home and that’s when I hooked it up to an odm and it gave me a p0700 and u0100 code for the past few days I’ve been trying to figure out what wrong with my car but I’m stuck with no where to go I put the stock header back on and it still won’t turn on anyone have any idea of what’s going on (it’s an automatic with no tune)

[jesusx]

Did you find the culprit? I'm getting exactly these 2 codes.

[tomm.brz]

is your car AT?

I would just try to disconnect battery 5 minutes and then reconnect and let everything reset
u0100 is very generic and harmless and you can ignore it
p0700 can be more serious

[RT-BRZ]

A "U0100" code on a Subaru BRZ indicates a "Lost Communication with ECM/PCM" which essentially means the car's computer (Engine Control Module/Powertrain Control Module) is not properly communicating with other vehicle systems, often caused by a faulty battery or issues with the vehicle's electrical wiring harness; it's a common code that can manifest with various symptoms like engine performance problems or dashboard warning lights.
Key points about the U0100 code:
Meaning:
The car's computer is unable to properly communicate with other modules within the vehicle network.
Common Causes:
Low Battery Voltage: A weak battery can disrupt communication between modules.
Damaged Wiring Harness: Damaged or corroded wires within the electrical system can disrupt communication.
Faulty ECM/PCM: In rare cases, the Engine Control Module itself may be malfunctioning.
What to do when you see a U0100 code:
Check the Battery:
Measure the battery voltage with a voltmeter. If it's low, charge or replace the battery.
Inspect Wiring Harness:
Look for any visible damage, corrosion, or loose connections within the wiring harness.




A "P0700" code on a Subaru BRZ indicates a malfunction within the transmission control system, which could be caused by various issues like low transmission fluid, a faulty shift solenoid, a malfunctioning transmission range sensor, or a problem with the valve body; essentially meaning there's a problem with how the transmission is being controlled by the car's computer system.
Key points about the P0700 code:
Generic code:
This is a broad code, meaning it doesn't pinpoint the exact issue within the transmission, so further diagnostics are needed to identify the root cause.
Potential symptoms:
Difficulty shifting gears
Hesitation when accelerating
Stalling
Rough driving
Reduced fuel efficiency
Possible causes for the P0700 code on a Subaru BRZ:
Low or dirty transmission fluid: Regularly check the fluid level and quality, and replace if necessary.
Faulty shift solenoids: These are electrical components that control gear changes, and a malfunction can trigger the P0700 code.
Damaged valve body: The valve body houses the transmission's hydraulic components, and wear or damage can lead to shifting issues.
Transmission range sensor malfunction: This sensor tells the car's computer which gear is selected.
Faulty wiring or connectors: Damaged wiring related to the transmission control module can also cause this code.
What to do when you see a P0700 code:
Have your car diagnosed by a mechanic:
They can use a diagnostic scanner to read the code and identify the most likely cause.
Check transmission fluid:
Check the fluid level and quality, and replace if needed.
Inspect for potential electrical issues:
Check for damaged wiring or connectors related to the transmission control module.



FFS people. Google is your friend.

[jesusx]

Originally Posted by tomm.brz

is your car AT?

I would just try to disconnect battery 5 minutes and then reconnect and let everything reset
u0100 is very generic and harmless and you can ignore it
p0700 can be more serious

Yes, it's an auto tranny. Both errors came up together.

[jesusx]

Appreciate your help. P0700 is a generic code but i cant seem to find more codes from the transmission module. It all started when i installed a supercharger, within a few months, a lot of weird things happened:

1. 15A HAZ fuse blown, causes indicators not working & shift lock stuck (problems fixed by just replacing the fuse)

2. EFI CTRL fuse blown short to ground, causes car stalls & unable to crank. (problems fixed by heat wrapping an exposed wire touching the ECU bracket)

3. Now facing this P0700 and U0100 problem. Initially the rpm drops and the traction warning light comes up. When the rpm raises back, the light went off again (check the video below). After a couple occurrences, CEL pops up and throws P0700 & U0100.

https://youtube.com/shorts/oHIA3U_Rmzo?feature=share

I wonder if all of the issues are correlated to each other (have a root cause) or just coincidence.

[jesusx]

I think i found the culprit. Wiring under the fuse box has oxydated, not sure if anyone has the same issue.
https://youtube.com/shorts/vxerhClLM...nM5Oxz4aW84EFY