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Speed sensor fault

Discussion in 'VN - VP Holden Commodore (1988 - 1993)' started by Pete O, Dec 27, 2019.

  1. Pete O

    Pete O Member

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    Hi guys, I have a speed sensor fault (code 24) coming up. My speedo works fine & the code doesn’t come up immediately but by the time I hit top gear it is there. Just before it comes up it hesitates for a second then it comes on. It is also doughy & drinking fuel like it is going out of fashion when the engine light is on.
    I have read some threads on it & am not sure if it is the sensor, the ecu or a wiring problem now?
    Anyone help me out with what one could possibly be the culprit. I’m going broke buying fuel....

    Cheers...........Pete.
     
  2. MikeC

    MikeC Active Member

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    Are you getting 12V at the speed sensor (pink/blue ?) power wire with the ignition on? Check the sensor earth (black/white ?) wire. I'd also check , break and clean with contact cleaner every connector between the speed sensor and the ECU.
     
  3. Pete O

    Pete O Member

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    Thanks MikeC, I only got home yesterday morning so I will check that out today. I had a quick feel under the car on my way home & it was actually loose & covered in oil so I tightened it as much as I could & kept going but it was still the same. I’ll give it a good clean up today & do the connectors as well.

    Cheers..........Pete.
     
  4. MikeC

    MikeC Active Member

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    Did you pull the ECU fusible link for 30 seconds to reset it?
     
  5. Pete O

    Pete O Member

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    Yes I pulled up & disconnected the battery for a couple minutes but it just came back.
     
  6. MikeC

    MikeC Active Member

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    If it came back without the car moving it's probably the wiring - the control system was doing communication checks with it's sensors. I'd check the wiring , if that's good it's time to have a look at the sensor.
     
  7. Pete O

    Pete O Member

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    First time today I done about 25k before the car coughed & spluttered then the light came on. Then I stopped after about 2 hrs & when I took off it came on again after about 2 km.
     
  8. MikeC

    MikeC Active Member

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    Looks like it's an intermittent fault, probably not the sensor could be wiring. According to my manual there are ways of testing the sensor that involve installing temporary resistors then turning it by hand and watching the voltage fluctuate wit a multimeter- I've never done it and the method is not simple to describe.
    Is the square drive in the center of the sensor engaging fully?
     
  9. Pete O

    Pete O Member

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    Oh goody, just what I need an intermittent fault that will take me forever to find, lol. I haven’t had the sensor out yet as I haven’t had time, I’ve parked the ute up until I get a minute to look at it. I’m in the middle of shifting house & don’t have any spare time. Bad time for the ute to start playing up.
     
  10. MikeC

    MikeC Active Member

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    The joy of owning an old Holden. I have an instrument cluster that's falling apart and a missus that wants to know why the old Statesman is cluttering up the carport.
     
  11. Pete O

    Pete O Member

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    Lol yeah, they just don’t understand do they....
     
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  12. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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  13. Pete O

    Pete O Member

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  14. Comcal76

    Comcal76 Member

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  15. Pete O

    Pete O Member

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    Thanks for that but the speedo works just fine at all times so I’ll just have to start at the sensor when I get time & work through all the fixes.
     
  16. delcowizzid

    delcowizzid on holiday

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    Vn speed goes from the sensor to the dash then to the ecu so if the dash is working the sensor should be fine. You may just need to reseat the dash back into the plugs to fix a bad connection
     
  17. Pete O

    Pete O Member

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    Ok thanks, I’ll try that. Could it still mean the ecu is toast?
     
  18. MikeC

    MikeC Active Member

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    Make sure all the wiring is right first. From memory code 55 indicates common ECU faults.
     
  19. Pete O

    Pete O Member

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    Ok thanks, the only code it is bringing up is 24 (speed sensor) so maybe it is a dodgy connection somewhere. Once I have finished moving house I’ll have a look at it & see what I can find.

    Cheers........Pete.
     
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  20. MikeC

    MikeC Active Member

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    Hi Pete,
    Did you ever solve this? I've developed the same intermittent code 24 error. My ECM is not putting out a 12V signal on circuit 437 , speedo works but cruise control doesn't.
    I've replaced the speed sender just before this happened. I checked delcowizzid's suggestion and checked the continuity between A10 and the green wire at terminal K on the cruise control= zero ohms so that total circuit seems OK.
    I recently fitted a MACE chip - could that do this somehow?
    I'm open to any suggestions before I replace the ECM.
     
    Last edited: May 4, 2020

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