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Hello everybody,

First of all sorry for my bad english, indeed I'm french. I've got an old 1999 996 Carrera 4 Tiptronic 85000km, I had recently an error that occured. While driving, D and 4 started to flash. I had bought a PIWI cable so I plugged my car to my laptop and I red the errors :

About to get fault codes

moduleType = TiptronicG40

dtcCount = 3

Fault Number: 93

Description: P1656 - Coolant shutoff valve

dtcCount = 3

I've found the pdf named "Diagnosis/troubleshooting Tiptronic SYSTEM G 40" and so I decided to perform the "test point 9" .

My problem is that I really don't know where to find this damned valve. It's been 3 days I've been looking for it, trying to find some answers on the internet, on this forum. I understood I have to look on the drivers side of the transmission... But I still don't know where it is...

Could someone help me please ? It's driving me crazy !!! Could somebody take a picture or draw me something to explain exactly where it is ? Last request,if it's possible , could someone give me the reference of this valve in order to buy one on the internet if it happens it's faulty?

Thanks a lot by advance to everybody. This forum is a miracle for me, you make a great job with this useful forum !!!


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  • Admin


P1656 Coolant shutoff valve - open circuiVshort circuit to ground, short circuit to B+

Possible causes:

- Shutoff valve

- Wiring

- Tiptronic control module

The coolant valve can easily be tested with the Durametric software, a PST2 or PIWIS tester. Drive links/Coolant shutoff valve -- the triggering pulse of the valve can be heard as a clicking sound. No click - replace the valve.

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Hello Loren thanks a lot for your response...

On my durametric, under drive links menu, I don't have Coolant shutoff valve ... That's why I can't test it like that...


I've got durametric 5.1.4 and no coolant shutoff valve under drive links...

Any idea to make it work, for sure it would be easier than to test resistance on pin 1 and 2 of the valve...

Thanks again


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  • Admin

Perhaps Durametric does not support that drive link.

If you can find someone with a PST2 or PIWIS tester this is not even a 5 minute job.

Otherwise I guess you could disconnect the valve electrical connection from the car a and try applying 12 volts to the valve and see if it clicks.

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Otherwise I guess you could disconnect the valve electrical connection from the car a and try applying 12 volts to the valve and see if it clicks.

Yes, this is what I wanted to do but I don't know where is the valve... the reason of my post ...




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Last request,if it's possible , could someone give me the reference of this valve in order to buy one on the internet if it happens it's faulty?




The part number for the automatic transmission heater water valve is 928.574.573.03 .

There is also a changeover valve, with part number 996.605.123.01.

I am guessing that you are referring to the changeover valve, but be sure to double check with your parts dealer in the event you do end up needing this part.

The heater valve is number 8 in this diagram, and the changeover valve has a red arrow pointing to it:


Bonne chance!

Regards, Maurice.

Edited by 1schoir
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  • 5 years later...

Sad, I'm getting this same error code but on a 97 Boxster. Too bad the OP never bothered to reply and update his thread. From alldata;



Coolant Shutoff Valve Open Circuit/Short To Ground, Short To B+
DTC 93
Fault Effect: The reduced driving program is activated if there is an open circuit/short to ground.
The fault is only entered in the fault memory in the event of a short circuit to plus.
The function of the coolant shutoff valve can be tested with the Porsche System Tester 2 (Drive links/Coolant shutoff valve).
1. Test valve with the Tester.
2. Check internal resistance of the valve. To do this, pull off plug connection on the valve and connect ohmmeter to pin 1 and pin 2.
Nominal value: 25 ­ 35 ohms
3. Check wire from the Tiptronic control module connector pin 51 to the coolant shutoff valve connector pin 1 for open circuit, short to
ground and short to B+.


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