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Car Dying With Speedo Cable, But Runs Perfectly Without...


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Hey Guys,

I did an RB20DET swap from an R32 into my Cefiro. I've also converted it from auto to manual.  The problem I'm having is that when I plug the speedo sensor cable into the back of the gauge cluster, it kills the car when I hit about 20km.  If I disconnect the speedo cable, it runs perfectly, but I can't see how fast I'm going. 

All of the other connectors work fine on the cluster, such as lighting, fuel gauge, temperature.  It's only when I connect the speedo cable in.  Before, when I was running the RB20E, it worked perfectly fine.

Do I have something not connected right?

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Was original Cefiro auto speedo sender electronic?

What speedo sender (from what origin car, gearbox, etc) is in the manual trans?

What does the speedo head in the Cefiro want as an input? Cable drive or electronic? (and I realise that what you have between the gearbox and dash must work, because you say when you plug it in you can see the speedo work, but I'm just trying to get the full picture).

What does your wiring diagram say about the signal line from the dash to the ECU? You do realise that the speed signal that the ECU watches is created at the speedo head, right? Whatever the speed signal into the speedo head from the sender is (and it could be mechanical drive, like in an R32, or it could be an AC voltage from an electronic sender like in an R33) then the speedo head translates that into a square PWM signal for the ECU. There could be a difference in wiring at the ECU between the original RB20E plug and the RB20DET. You could be putting the speed signal into the wrong place on the ECU.

The RB20DET ECU can and will run without a speed signal. Just some functionality doesn't work properly as a result. But this used to be the stupid bogan way of beating the 180k speed cut. So we know that the ECU doesn't absolutely need a working speed signal to run the engine and drive at more than 20k. But putting the speed signal into the wrong input on the ECU could be quite a bad thing to do.

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