Intermittent no start problems from a bad computer ground 

Intermittent no start problems from a bad computer ground.
2000 Audi S4 Quattro 2.7 Turbo.
The procedures shown in this video apply to ALL make and model cars. When you understand circuit designs like the 5v reference and sensor ground paths, these types of problems are very easy to identify. The problem on this Audi was revealed within the main sensor circuits (MAP and TPS etc) and was quickly narrowed down to a sensor ground problem.
Symptoms:
random stalling problems
intermittent no start
clicking noises under the hood when not starting
no communication with scan tool
throttle body motor clicking rapidly
Fix:
tightened loose computer ground eyelet located on the firewall
Test procedures shown:
electronic throttle body tests
throttle position sensor signal tests with a scope
MAP sensor signal circuit
sensor ground circuit
computer ground circuit
how to quickly identify a ground circuit problem
what is the difference between a sensor ground and computer ground
how to check main computer grounds
Tools used:
scan tool
labscope
Digital multimeter (can be used instead of a scope)
Related videos:
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MAF sensor trouble code (P0102) caused by a bad ground
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How to test a starter motor (No Crank Testing) bad ground
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Fuel Pump Relay Problem
• Fuel Pump Relay Problem
Playlist:
ground circuit problems
• ground circuit problems
For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
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