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9 Answers

03 cts problems

Asked by: 28 views Trouble Code Questions

Caddillac cts 2003. I just replaced the ecm and brake light switch. 118k miles. It will mot shift out of park. Abs,brake,and t/c lights are on. I\’m a little desperate for help and advice. F1 F6 DIAGNOSE shows codes


9 Answers

  1. 0 Votes Thumb up 0 Votes Thumb down 0 Votes

    Hello Ilaria17

    Sounds like a tricky problem but should not be impossible. To start with I’ll try to write the fault codes with easy words

    P0856 – PCM (powertrain) or Brake module is not getting signal from ECM ( engine control module )

    P0318 – Faulty signal/Rought from either rought sensor or ABS wheel speed

    U1000 – Lost communication with PCM / ECM, depends where you find this fault

    U1040 – No vehicle speed information

    If you delete the fault codes, which fault codes come back?
    If you go into measurements/live data in the Powertrain control module and see data from following:
    Gear information
    Speed information
    Brake switch information

    And do the same see if you can see this information in the Brake control module and Engine control. And there you could probably figure out where the information is lost!

    Sellen - Dec 12, 2017 |Reply

  2. 0 Votes Thumb up 0 Votes Thumb down 0 Votes

    I cleared the codes and they all come back.

    I didn’t have any of them before I replaced the ecm. I purchased the ecm from eBay already programmed to my vin. I’m starting to think it’s a faulty ecm

    Ilaria17 - Dec 12, 2017 |Reply

  3. 0 Votes Thumb up 0 Votes Thumb down 0 Votes

    If you got the fault codes after you replaced the ecm I would have tried to locate the first problem with the old ECM if it does not give those fault codes with it.

    Also with the old ECM see in Powertrain Control Module live data for speed information, gear information, brake light switch information to locate why you cant get the P gear out!

    Sellen - Dec 12, 2017 |Reply

  4. 0 Votes Thumb up 0 Votes Thumb down 0 Votes

    I didn’t run the codes with the old ecm. I replaced it because I couldn’t get the car to start at all. I have been told by several mechanics to replace the shift interlock solenoid.  But before I spend another 80$ I want to know someone else opinion. I want to thank you for the fast replies

    Ilaria17 - Dec 12, 2017 |Reply

  5. 0 Votes Thumb up 0 Votes Thumb down 0 Votes

    Okay I understand, and the car only start with the new ecm and before replaced ecm everything worked as usual?

    Sellen - Dec 12, 2017 |Reply

  6. 0 Votes Thumb up 0 Votes Thumb down 0 Votes

    Yes the car only starts with new ecm.

    Before I replaced ecm I was only getting some codes related to 02 sensor. But that was with a obd2 reader. I wasn’t aware of the F1F6 diagnose. I didn’t have a brake or t/c or and light on. It all came on after I installed the ecm and cracked the car up

    Ilaria17 - Dec 12, 2017 |Reply

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    I think your problem with the new ECU is that the Variant coding is wrong.
    Is the article number 100% the same as old?
    The new ecm could be variant coded as a manual car.

    Any workshop with the right normal bosch diagnostics or something likely would be able to code it for you.

    Sellen - Dec 12, 2017 |Reply

  8. 0 Votes Thumb up 0 Votes Thumb down 0 Votes

    I attached a photo of old ecm. There is a IV/4 code.
    The new ecm has a IV/2 CODE is that a deal breaker

    Ilaria17 - Dec 12, 2017 |Reply

  9. 0 Votes Thumb up 0 Votes Thumb down 0 Votes

    You should see a 8 digit General Motors (GM) number on a white label on the ECU

    example: 12580807

    If the number is the same, take it to a workshop that can code it for you! 🙂

    Sellen - Dec 12, 2017 |Reply

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