996 Crank Position Sensor replacement info

[slknv]

Hi guys

Had my 996 hibernating in the garage for about a month now as it refuses to start. First problem was low voltage while driving and not starting when hot - (already collected parts to replace the starter/alternator cable, alternator regulator, drive belt etc) but then it just won't start at all from cold.

After a bit of research I reckon it would be the crank position sensor, so had a wait a while for one to arrive from overseas. Has anyone replaced the CPS themselves on a 996? Been searching for a good DIY guide but can't find one - from what I've read, jack up the car, remove rear (left?) wheel, unbolt a 5mm hex holding in the CPS and unclip harness, then install new one. 

 

[Avon]

Yes I have done it - its pretty straightforward.  I found tapping a hex bit into the retaining bolt and using a 1/4" rachet helped to get it out more easily than using a normal elbow allen key.

Also take a good look / photo of the position of the plugs and clips before unplugging the old cable - its easy to forget where it all is routed when the old one is hauled out.

 

Not sure it will fix the problem though - but its worth a try.  Have you checked all your fuses?  Could be something as simple as a popped starter circuit fuse.

[slknv]

Good advice on checking fuses - will do that before I break out the toolbox! Other tips also good too, thanks

Will try and take a whole bunch of photos etc and write it up in the diy forum.

[Redracn]

Have you considered a cheap OBDII tester. It can show if the ECU has emission related errors and also show the RPM which is from the crank position sensor. If the cranking RPM is plausible then the chances are there is nothing wrong with the sensor. 

[Stephen Tinker]

Try these before you loosen the tool roll:

1) Make sure your battery is up to full charge - you want to see 12.6v @ the terminals.

2) Can you hear the fuel pump run when you switch on the ignition? It stops after about 3-4 seconds as it pressurises the system.

3) When you crank the starter, does the tach move slightly?  If it moves its getting the signal from the CPS - if it remains static, your CPS is probably faulty.

[slknv]

Thanks everyone for helpful tips!

On 7/18/2018 at 11:17 AM, Avon said:

Yes I have done it - its pretty straightforward.  I found tapping a hex bit into the retaining bolt and using a 1/4" rachet helped to get it out more easily than using a normal elbow allen key.

Also take a good look / photo of the position of the plugs and clips before unplugging the old cable - its easy to forget where it all is routed when the old one is hauled out.

Not sure it will fix the problem though - but its worth a try.  Have you checked all your fuses?  Could be something as simple as a popped starter circuit fuse.

• Yep, as recommended used a 5mm hex and ratchet, came out easily.
• Took photos, still managed to install the bracket with the variocam cable trapped behind it. Swore, removed and reinstalled it properly.
• Checked fuses - all seemed good.

 

On 7/19/2018 at 10:02 PM, Redracn said:

Have you considered a cheap OBDII tester. It can show if the ECU has emission related errors and also show the RPM which is from the crank position sensor. If the cranking RPM is plausible then the chances are there is nothing wrong with the sensor. 

• I've got an autel, didn't record any new codes when the car wouldn't start. Didn't even think to try a realtime monitoring of RPM - very good tip that one though.

On 7/20/2018 at 11:33 AM, Stephen Tinker said:

Try these before you loosen the tool roll:

1) Make sure your battery is up to full charge - you want to see 12.6v @ the terminals.

2) Can you hear the fuel pump run when you switch on the ignition? It stops after about 3-4 seconds as it pressurises the system.

3) When you crank the starter, does the tach move slightly?  If it moves its getting the signal from the CPS - if it remains static, your CPS is probably faulty.

• Brand new battery 2 months ago, and regularly on a ctek. Multimeter read over 12.6
• Maybe my ears are bad, I can never hear the fuel pump priming in this car (I hear is in my other cars though!)
• No movement of tach - that was one of the main symptoms that made me suspect CPS.

Anyway, did a DIY writeup in case anyone else needs some pointers - thanks again guys

 

 

tim

[Avon]

Good stuff, glad it has got you up and running again!