I am sitting with a problem that is slowly draining my wallet. I drive a opel corsa utility 14i, and after having to replace a blown head gasket, all sorts of gremlins started popping up. First no fuel coming through, and after taking out the fuel tank and the pump, the pump was way under pressure so the pump got replaced. Now there is fuel and spark, but the car still wont run. It starts for about a second and then stops. Checked for loose connections and all that, and everything is fine. Then I decided to check the CPS (Crank Position Sensor). Starting on the ECU side I checked for voltages. The corsa uses a 3 pin arrangement, where pin 1 is the 5 volt supply line, pin 2 is the 12 volt signal line and 3 is the ground. I tested with the car switched on to where the dash lights come on, but not started. Now this is where I need help. The 5 volt supply reads about 5.2 volt, but the 12 volt signal gives 0.00 volt. Am I testing correctly or do I have a bigger problem?

  • What does the signal voltage do when the engine is cranked? Have you checked for a short to ground?
    – Ben
    Commented May 18, 2018 at 1:16
  • Hi Ben. The signal voltage stays at 0.00 volt Commented May 18, 2018 at 9:21
  • If you have spark, i’d say the crank position sensor is ok and possibly the testing is incorrect. In general OEMs use the ckp sensor for ignition timing. You might want to try testing at the sensor it self with an extension lead on the com line to the battery - terminal.
    – Ben
    Commented May 18, 2018 at 11:01

2 Answers 2


Have you plugged it into a scanner to see if there is any fault codes and to look at the live data? Without doing so you're just stabbing in the dark and possibly wasting time.

Running only for a second or two can be symptom of a immobiliser fault. Have you swapped the ECU, Instrument Cluster or any other electrical component recently?

There is a common fault with petrol Corsa C's where the internal 5V circuit in the engine ECU fails. To eliminate this you can load test every 5V output on the ECU or send the ecu for testing at a specialist.

You haven't said what year which doesn't help

  • Hi Terry. Thanks for the reply. I am just a average Joe and unfortunately don't possess a scanner, only a multi meter. I also lost my work about 3 months ago and battle to find anything at all, so I am forced to make due with what I've got. The only electrical component changed was the fuel pump. The ecu, instrument cluster, immobilizer are still the original components that came with the car. The car in this case is a 2000 Opel Corsa 1.4i Utility. Like I said, the 5 volt is measured at the plug where the Crank Position Sensor and the ECU connects under the bonnet. It is a 3 point connector Commented May 18, 2018 at 9:18
  • that has pin 1 for the 5 volt supply, pin 2 for the apparent 12 volt signal and then pin 3 which is ground. Commented May 18, 2018 at 9:19
  • oops, forgot to say that it is a B series corsa Commented May 18, 2018 at 9:25

On ckp sensors I've always tested to make sure the supply wire does indeed have voltage (usually 9-12v). Make sure the ground is indeed grounded. On a 3-wire that third wire would then be your signal. You need to pierce that wire (back-probe) with the connector plugged into the sensor. While cranking engine you should be seeing an ON - OFF voltage equal to supply voltage. Like stated earlier, if you have spark, the ckp sensor is good.

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