P1350 – Ignition Control System P1375 – IC 24X Reference Circuit High Voltage.

Tiny
CISCOJOE
  • MEMBER
  • 1999 CADILLAC STS
  • V8
  • FWD
  • AUTOMATIC
  • 105,000 MILES
One day, while driving, the service engine light came on. Engine immediately ran rough, with numerous stalls, and tach did not work. I checked the codes and retrieved: P1350 – Ignition Control System P1375 – IC 24X Reference Circuit High Voltage. Shortly later the car ran as it should again, service engine light went out, and the two above codes were then marked as History Codes. This was happening constantly, and on a few occasions I also retrieved the following, which would also be marked as a History code when engine reverted to normal operation: P1377 – IC Cam Pulse To 4X Reference Pulse. I checked all ICM connections, plug wires for leakage, etc. This car also has had both crankshaft position sensors replaced in the distant past, due to a service bulletin. I then replaced the ICM/Coil Pack, with a used unit. Car started right up, and ran fine. No issues. As I had the car parked in driveway running for an extended period of time it then stalled as if someone had turned the key off. Would not start, or even fire a cylinder. After it was allowed to sit for an extended period of time (cooled off), it started right up. I assumed I got a bad used ICM/Coil pack and returned it for another. Same exact issues. Car still randomly lights up service engine light, P1350 and P1375 codes always come up together when it does, and if I let it run, but not drive, after an extended period of time it stall as if someone tuned of the key. Next I replaced the PCM. I had a programed unit overnighted to me from www. Autoecms. Com. Car started right up, after I recoded the key for the security system. Let it run in driveway for a while, same issue, with P1350 and P1375. Car cools of, back to normal. I now change both crankshaft position sensors, wer as the wer chnaged years ago. Get that done, same exact issues. Aslo, when the cars runs rough, and the codes are active, with the service engine light on, the tach does not work. Looking for incite in this issue, were as the car has told me all it can!
Friday, January 28th, 2011 AT 7:34 PM

2 Replies

Tiny
FACTORYJACK
  • MECHANIC
  • 4,159 POSTS
Hello,

This will be a connections issue or the PCM needs ot be replaced, here is a guide to help confirm the issue by checking the wiring using the engine wiring diagrams below.

https://www.2carpros.com/articles/how-to-check-wiring

You can get a rebuilt PCM just give them your VIN and they will program it for you. Check out the diagrams (Below). Please let us know what you find. We are interested to see what it is.
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Saturday, January 29th, 2011 AT 6:03 AM
Tiny
SRLAWSON
  • MEMBER
  • 1 POST
Thank you for this post I had this problem and had to get a rebuilt PCM cost me $154.00 all fixed! I love this site.
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Saturday, August 10th, 2019 AT 4:14 PM

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