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Chevrolet Express
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2018 Express wiring

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Old Jul 26, 2025 | 8:12 PM
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hoffy30's Avatar
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Default 2018 Express wiring

Just bought a new to me 2018 Express with the Quigley 4x4 conversion. Used in law enforcement for transport of ?. Had a ton of aftermarket wiring for radios, computers lights etc. They basically cut everything off before removing their gear. Most of this was not a problem and it was a well done installation BUT there was a device wired in called a secure-idle, some sort of device where they could leave the van running without keys and it would shut down if the brake was applied. The cruise control was not working when I bought the van, switch on steering wheel lights up but no light on the dash and will not engage. After gaining access to the area
brake switch to instrument panel plug
brake switch to instrument panel plug
behind and under the wheel found where they had tied in to the ignition circuit. Removed all of the wiring for the secure-idle and repaired where the tie in was. All good except there were 2 wires as part of this device that went to the plug servicing the brake light which then is supposed to go to the instrument panel wiring. Can not find anywhere these 2 wires are supposed to go, The black is a ground and a lt blue has power when brake applied. Reasonably sure this is my CC problem but am stumped as to where this ties in. Attached picture shows the plug and where it is mounted. Any ideas or anyone have there dash apart that could look at their set up. Any help greatly appreciated.
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Old Jul 27, 2025 | 9:21 AM
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Derrick71's Avatar
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I don't have a complete answer but this is a thread has a little bit I learned about the brake light switch and cruise control relationship.

https://chevroletforum.com/forum/exp...t-time-116080/
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Old Jul 27, 2025 | 10:02 AM
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Thanks for the link. Have a new brake switch to try but until I can find where the wires off this plug go I am stuck.
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Old Jul 27, 2025 | 11:10 AM
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Try looking in the wiring diagrams of the GM Upfitter manual. They are quite complete and would have been used by the people that installed all that stuff.
https://www.gmupfitter.com/wp-conten..._2017NOV06.pdf
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Old Jul 27, 2025 | 1:28 PM
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Have been on the upfitter site and identified the harness as X206 which is the Instrument panel harness to instrument panel harness. It describes the location as left side by headlight switch. There is no locator view. Nothing in this area except the headlamp switch itself . A picture of of where this connects would be invaluable. Thanks for the responses
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