Fans running constantly with PSI harness

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03-19-2015, 06:50 PM

cpd004

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Fans running constantly with PSI harness

Ls3 running a Psi harness and ecm, and the output to each fan almost immediately after the car starts supplies negative regardless of engine temp. The odd thing is, when a Power Probe is connected to the fan trigger wires from the ecm, it's not a consistent negative output, but broken up....kind of like -----.-..-..-...-------.-.--. It is enough to energize the relay and run the fans.

Last edited by cpd004; 03-19-2015 at 07:11 PM.

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03-20-2015, 06:07 AM

L92 OLDS

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This is why I'm making my own harness. Sounds like a bad connection somewhere. Can you use a multi meter to check directly at the ECM?

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03-20-2015, 09:08 AM

slowsol95

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On my ls1 Sonoma with a frost mail order tune if the check engine light is on the fans will automatically run on low speed.

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03-20-2015, 09:12 AM

M6 Swap

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in the PSI instruction manual it says if the fans run constantly, make sure you have a check engine light wired in properly, if not the fans will run. Look in the back 2 pages of the instructions that's where troubleshooting is located.