2007 Cadillac Dts crank start then dies immediately?

Tiny
AHOLMES88
  • MEMBER
  • 2007 CADILLAC DEVILLE DTS
  • 4.6L
  • V8
  • 2WD
  • AUTOMATIC
  • 164,592 MILES
2007 Cadillac Dts will crank over and start then dies immediately. Had a code p1682 for ignition switch. Changed that and still getting the same results. Going to code agian since putting ignition switch on to further diagnose. Was maybe thinking crank shaft sensor or cam and wanted to know the location of both and what would cause a crank start then stall symptoms
Sunday, March 8th, 2026 AT 9:00 PM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 55,535 POSTS
Hello,

This code indicates the ECM sees a voltage mismatch between two ignition power circuits. So I would check the fuses and swap out the relays in the diagrams below, these are the main voltage feeds into the PCM

P1682 - Ignition 1 Switch Circuit 2

After that if the codes comes back, with the key on you may want to check the voltage inputs at the PCM, and I would check the grounds as well. Here are the locations for those as well. If these are okay I would replace the PCM. Check out the images (below). Let us know how it goes. Ken
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Tuesday, March 10th, 2026 AT 8:21 AM

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