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Old 08-06-2018, 03:38 PM   #6
fdryer
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Join Date: Jan 2006
Location: NYC
Posts: 43,610
 

2003 L-Series 3.0L Sedan
Default Re: Secondary air injection system

Electronic circuits can be confusing if not familiar with some quirks. Electronics sometimes forgoes using a relay to power solenoids. When this occurs, a power transistor is used. When an electronic circuit switches a power transistor off, residual voltage may be seen on the output side, where you're measuring at the solenoid connection. This is residual voltage with zero current behind it. With zero current at the wire, the solenoid isn't powered. Ignore it. Ask you need to know is if the solenoid powers up and if it opens or closes its own valve.

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