When to use "Use High Speed" and when not

I was reading 2006 Hummer H3 3.5 with P12 ECM.
It did stop reading the ECM at different times and I was not able to finish the reading until I un-ticked the Use High Speed option in the Vehicle Reader window.

Is there any rule of thumb when High Speed reading should be used and when not?

Using MPVI2 with firmware version 3.0.30 and VCM Editor 4.5.1162 Beta.

Are there any similar actions needed when writing?

when you need to select low speed mode it means you've got issues usually wiring issues or possibly battery related issues that really NEED to be resolved BEFORE you attempt to flash to the vehicle.

Don't ever forget to buy an effective and useful obd2 scanner as always. This will help you track and know vehicle problems. One brand that is highly recommended ist the Innova https://bestobd2scanners.com/innova/. Know on the review why.

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Originally Posted by bjorgvinben

I was reading 2006 Hummer H3 3.5 with P12 ECM.
It did stop reading the ECM at different times and I was not able to finish the reading until I un-ticked the Use High Speed option in the Vehicle Reader window.

Is there any rule of thumb when High Speed reading should be used and when not?

Using MPVI2 with firmware version 3.0.30 and VCM Editor 4.5.1162 Beta.

Are there any similar actions needed when writing?

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Does the vehicle have any type of aftermarket radio/head unit?

The radio seems to be original.
There is VHF installed which I will remove the fuse from next time I will have access to the vehicle along with checking on the battery voltage.