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P0719 Brake Switch Circuit Low Issue in 1997 GMC Sierra Z71 5.7L - Diagnosis and Fixes

Model: GMC Sierra Z71 Fault Code: P0719 Posted: 2008-04-29 21:40

My 1997 GMC Sierra Z71 with a 5.7L engine has recently returned the P0719 trouble code — 'Brake Switch Circuit Low/Input'. The truck currently has 160,000 miles on it and was originally owned by someone else. I've had the transmission flushed every 45,000 to 50,000 miles, which I believe helps maintain performance. After clearing the P0719 code on Saturday, I drove approximately 45 miles before it reappeared. The truck shifts and runs normally under normal conditions. This issue has previously appeared last year as well — cleared then, driven about 15,000 miles later, and the code returned again. I also have a Hypertech Power Programmer installed with power tuning; however, the system is set back to factory performance specifications. Despite this, the P0719 code persists. I'm seeking advice on how to properly diagnose this issue. Is there a known cause for recurring P0719 codes in 1997 GMC Sierra Z71 models? What should I check first — such as the brake switch or wiring circuit? Any guidance on where to start would be greatly appreciated.

Related fault codes
P0719
Comments (3)
Anonymous 2008-04-30 11:03

Have you tested the brake switch or its electrical circuit using a digital multimeter (DVOM)? Also, do you have access to a manual or wiring diagram for your vehicle's braking system and transmission control?

Anonymous 2008-05-06 17:30

I forgot to include this detail in my original post — the P0719 code also relates to torque converter lock-up. I'm unable to locate the brake switch location in my Chilton's manual. Are there any reliable diagrams or links available for identifying the switch? Any help would be very much appreciated. To clarify: no, I have not tested the switch or obtained a wiring schematic.

Anonymous 2008-05-07 06:36

How does P0719 specifically relate to torque converter operation? Note that torque converter-related codes fall in the range P0740–P0744. First, verify the brake switch and its circuit using a digital multimeter (DVOM). If the electrical components appear functional, consider whether the Hypertech Power Programmer might be generating false or incorrect signals — some users have reported this issue. I recommend contacting Hypertech directly for technical support on this matter.