P1654 - Coolant shut-off valve final stage

[samuel.mercer]

Hi all,

Does anyone have any idea what may be causing this error to show up when I use the Durametric software to query the ECU errors? Also, I don't seem to be able to clear the error.

It is related to the issue with my coolant temperature gauge throwing an error intermittently. I have had the coolant temperature sensor replaced, and coolant system purged and new coolant put throughout.

Thanks in advance, I would love to get to the bottom of this before I have to give all my money to the dealership....

Sam

[Loren]

P1654 Coolant switch-over valve driver, above limit value

Possible fault causes:

- Short circuit to B+ in control line

- Coolant switch-over valve faulty

- DME control module faulty

If you clear it does it come back?

[samuel.mercer]

Hi Loren,

Once i get the intermittent issue with the coolant temperature gauge there are two error codes/messages:

P3081 - Coolant temperature implausible

P1654 - Coolant shut-off valve final stage

I attempt to clear them using the durametric software, and the coolant temperature gauge returns to 80 (middle) and the fault exclamation light goes out. However the P1654 remains.

Now, this is the strange thing, and may give the best information yet as to what the fault might be: if I leave the car idling the gauge stays at 80 indefinitely. However, when I drive off, after a few miles it will fail again, and give the two errors above.

My best idea is that it is something to do with a short somewhere that only becomes an issue at low temperatures, or when low temperature air is operating around a certain area of the car's engine. Once failure has occurred, if I leave the car idling and stationary for 3-4 minutes, it will correct itself and the fault P3081 disappears. Maybe this is because the warm engine is heating up the part of the car that contains the short or whatever, that would otherwise not get warmed up if there was airflow over and under the vehicle. Also, in summer it is never an issue....

Hope this gives more info that could lead someone to be able to help!

Sam

[Loren]

P3081 Coolant temperature sensor function

Possible fault causes

- Open circuit, short circuit to B+ or short circuit to ground in sensor line to coolant temperature sensor

- Open circuit in ground supply to coolant temperature sensor

- Coolant temperature sensor faulty

- Thermostat faulty (stuck open)

- Tiptronic vehicles only: coolant shutoff valve open (mechanical fault, lack of vacuum…)

- DME control module faulty

I am not sure what actual values you can read on the Durametric for 997-1's - but I would look and see what the sensor values are to try to narrow down the problem.

[samuel.mercer]

Hi Loren, thanks again for the input.

I've had a look at the 'actual values' section of the Motronic DME but there appears to be no information on sensor values. Temperatures are all as expected though, engine, coolant, oil, transmission.

I did something interesting today, I cleared down all faults and queried for faults as I drove along. The first to appear was the P1654, which seemed to trigger the other. Hence I think that if we can sort out the P1654 then perhaps all the others will go away too.

From your original post you said this was probably one of three possible reasons:

1. Short circuit to B+ in control line

2. Coolant switch-over valve faulty

3. DME control module faulty

1 Appears to me to be the most likely, judging by the fact that it is intermittent, and temperature/humidity related. Could you possibly help point me in the direction of how to test for this, and subsequently how to get it resolved?

As ever I much appreciate your help!

Sam

[PTEC]

Your car is a tiptronic right? Have you check the operation of your coolant shut off valve? You can physically see the valve move back and forth when its actuated. If it doesn't move check the valve for vacuum leaks. If its tight then check the electric changeover valve for the shut off valve.

Edited March 10, 2010 by PTEC

[samuel.mercer]

Your car is a tiptronic right? Have you check the operation of your coolant shut off valve? You can physically see the valve move back and forth when its actuated. If it doesn't move check the valve for vacuum leaks. If its tight then check the electric changeover valve for the shut off valve.

Thanks for this, can you tell me where to look? Guess I need to jack up the car?

[PTEC]

Your car is a tiptronic right? Have you check the operation of your coolant shut off valve? You can physically see the valve move back and forth when its actuated. If it doesn't move check the valve for vacuum leaks. If its tight then check the electric changeover valve for the shut off valve.

Thanks for this, can you tell me where to look? Guess I need to jack up the car?

Well if its a tiptronic you'll be looking on the drivers side of the transmission. There is an electrically operated vacuum switching valve and the vacuum operated coolant shutoff valve in the same general area on the side of the transmission.

[MARCO BOK]

Hi all, I have the same problem with my Boxster, can someone help me with this? :oops: @ Samuel Mercier : how did you resolve the problem? :lightbulb:

Thanks!

[Ashman1957]

I have the same issue on a 997.1 3.6 Tiptronic. Anyone got to the bottom of it yet?

[JFP in PA]

12 minutes ago, Ashman1957 said:

I have the same issue on a 997.1 3.6 Tiptronic. Anyone got to the bottom of it yet?

 

Welcome to RennTech 

 

Which of the two codes discussed do you have?

[Ashman1957]

P1656 coolant shutoff valve & state: Current Driver, coolant change-over valve.

then P2181 Pending Cooling System Performance 

[JFP in PA]

30 minutes ago, Ashman1957 said:

P1656 coolant shutoff valve & state: Current Driver, coolant change-over valve.

then P2181 Pending Cooling System Performance 

 

Most probable issue is the Tips coolant change over valve has an issue or is not functioning properly.

[Ashman1957]

Thanks. Not sure my Indy knows what to do!

[JFP in PA]

11 minutes ago, Ashman1957 said:

Thanks. Not sure my Indy knows what to do!

 

Not an uncommon problem as diagnostic data is hard to come by as Porsche no longer publishes it, these valves are a bear to get at, and difficult to diagnose where the fault lies (e.g.: Is it an electrical problem such as a wiring short, or a mechanical fault in the valve itself) because a lot of scan tools cannot even see the Tip computer, much less see why it is upset.  And if it is the valve itself, it isn't cheap and can be problematic to swap out because of where it is on the side of the trans.  Larger issue is that if the valve is malfunctioning, it can overheat and kill the Tip, which will definitely make your wallet a whole lot easier to sit on.............

[Ashman1957]

Just to add. The car is 2007 997.1 3.6 Tip. & has just had new coolant pipes, front to back. New LTT fitted. Also PSE removed & Aftermarket sports back boxes fitted. Engine out & new RMS.

[JFP in PA]

3 minutes ago, Ashman1957 said:

Just to add. The car is 2007 997.1 3.6 Tip. & has just had new coolant pipes, front to back. New LTT fitted. Also PSE removed & Aftermarket sports back boxes fitted. Engine out & new RMS.

 

I'm intrigued by the replacement of the coolant pipes; did your indie do this using a vacuum refilling system per the factory/dealer methods, or did they just refill and "burp" the system?  Reason I ask is if it was done just before this issue cropped up, you could have a trapped air pocket in the Tip's cooling loop, which could be an easier and cheaper fix.

[Ashman1957]

2 minutes ago, JFP in PA said:

 

I'm intrigued by the replacement of the coolant pipes; did your indie do this using a vacuum refilling system per the factory/dealer methods, or did they just refill and "burp" the system?  Reason I ask is if it was done just before this issue cropped up, you could have a trapped air pocket in the Tip's cooling loop.

Just to add. The car is 2007 997.1 3.6 Tip. & has just had new coolant pipes, front to back. New LTT fitted. Also PSE removed & Aftermarket sports back boxes fitted. Engine out & new RMS.

 

the work was done prior to the problem. But the system has been drained & refilled using vacuum by another Indy closer to home to avoid driving distance. Alert on dash says (picture of thermometer) failure indicator.

[Ashman1957]

[JFP in PA]

Whomever you choose to work on this car needs to start by testing the coolant sensor and change over valve electrical circuits for shorts and open circuits to eliminate the sensor and valve wiring from the equation; if the sensor and the electrical circuits are good, the valve itself is bad, which can be confirmed by measuring the valve's inlet and out let coolant temps with a non-contact pyrometer; if it is not opening when it should, it is jammed. 

[Ashman1957]

Took the car 8 miles today for fuel, the rubber coolant hoses in front of the front wheels were both warm.. however the coolant in the expansion tank was still cold.

[JFP in PA]

1 hour ago, Ashman1957 said:

Took the car 8 miles today for fuel, the rubber coolant hoses in front of the front wheels were both warm.. however the coolant in the expansion tank was still cold.

Sorry, but that is meaningless, the hoses that need to be checked are under the car, alongside the transmission, and barely visible with the car on a lift.  You can see the cooler, control valve, and lines in this photo:

 

[Ashman1957]

I was just thinking the coolant might not be circulating with warm water at the front of the car but cold at the back. Really I want to take the car back to the indie who did the work but it’s 60 miles away. Don’t want to risk the drive if the coolant is not getting round as it should.

[JFP in PA]

57 minutes ago, Ashman1957 said:

I was just thinking the coolant might not be circulating with warm water at the front of the car but cold at the back. Really I want to take the car back to the indie who did the work but it’s 60 miles away. Don’t want to risk the drive if the coolant is not getting round as it should.

 

Unfortunately, these are two separate cooling loops, the temperature of one is no indication of what the other is doing.  And I would not suggest driving it any distances.