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Tigra Twintop 1.8 AT Z18XE AF17
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Discussion Starter · #1 · (Edited)
Explanation of C1500 fault code for the Electric Power Steering EPS.
Applicable to Meriva A, Corsa C, Tigra B, possible Meriva B but I don't know for sure.

C1500 means Invalid Torque Sensor Signal. Which are actually 2 potentiometers inside the steering column assembly.

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Fault code set criteria, the output signal of any of the potentiometer 1 or 2 above 4.5V or below 0.5V at terminals 4 or 8.

Repair manual says either torque sensor defect or the EPS control unit.

This is the electrical diagram.

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Wire colors Violet and Blue.

To proper diagnose this, I set an oscilloscope to these 2 terminals, measured against battery minus.

There is no way this can be diagnosed with a multimeter, neither with processed diagnostic data, forget about it, at least not how this vehicle behaved.

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This is how the reading looks like, when turning the steering wheel. Signals should be in opposition to each other, you can clearly see that the blue line, blue wire pin 8 shows a dirty potentiometer track or even maybe carbon track wear and tear. Also pretty obvious its signal goes below 0.5V, you should of seen the steering behavior, sometimes even turning by itself.

Now, these are filtered channels, EPS will filter as well, but both signals were pretty noisy.

Conclusion: defect torque sensor assembly. It is sold as a separate component.

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Good info there.
Often wondered what was inside that torque sensor.
I've a spare column with ecu and motor which am hoping to fit to a classic Ford at some point so this is a good start.
 

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Tigra Twintop 1.8 AT Z18XE AF17
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Discussion Starter · #3 ·
You would need a vehicle speed signal and engine speed signal in pwm format. I have a video on that engine speed signal:

 

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Thanks for posting that most appreciated.
Getting an engine speed signal wouldn't be a problem as I'm using a trigger wheel on the engine for a standalone ecu. The car speed is going to be more difficult as there's no electronics involved! Maybe a toothed gear something like an ABS ring?
 

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There is an EPS thread on here somewhere which shows the torque sensor dismantled.
 

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Discussion Starter · #6 ·
Thanks for posting that most appreciated.
Getting an engine speed signal wouldn't be a problem as I'm using a trigger wheel on the engine for a standalone ecu. The car speed is going to be more difficult as there's no electronics involved! Maybe a toothed gear something like an ABS ring?
Older cars had a converter build into the instruments, where the mechanical speed cable came in, from the gearbox. Or on the gearbox itself.
 
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