SAI pumps didn't come on this morning, how come?

[cfiiman]

Hey all,

I had an SAI failure (bank 2) a couple weeks ago on my 04 CTT so had to install a new pump on the driver's side and also removed and cleaned the check valve, etc. System has worked perfect since then and it solved the CEL issue associated with the bad SAI pump. This morning I noticed when the wife started the car to go to work there was no higher idle/whine like normal, it sounded like a warm start where the idle was already at 700'ish rpms and the pumps were not on. No CEL or anything and it is not a atypical hot morning or anything so what's going on? I've never not heard them run on a cold start, and it was both the pumps, not just one, almost like the ECU was telling them not to turn on. I have Durametrics and will try to activate the system this evening but I didn't have time this morning. The car has been sitting in the garage since yesterday evening when I pulled it in from the driveway around 8pm so more about 12 hours. Everything runs perfect just weird that this is the first time I haven't heard the pumps come on with the higher idle like a normal cold start up and was wondering if anyone knows why? It was my understanding they are to come on every time on cold start 

[Loren]

 

Always check the fuse first.

If the fuse tests good then put Durametric on it. I believe you can run it manually from Durametric - so try that too.

[cfiiman]

Hi Loren,

 

I definitely will this evening, but to my recollection aren't the bank 1 and 2 pumps fused separately?  Seems very odd both would blow as neither pump was on.  I'll put it on Durametrics as well tonight and report back.

[Loren]

Yes, in the E-Box FS3 and FS4. Both are 40A.

[cfiiman]

Well I just found out from calling Durametrics that activations are not supported on the 04 CTT engine module so I can't activate them.  I did check the 40amp fuses and they are fine along with Durametrics not finding any fault codes preset (and no CEL obviously either).  Not sure what else to do at this point.  I wouldn't think anything is amiss if I hadn't heard my wife start the car and noticed the pumps were not on.  Only other thing I find odd is after the car is shut off after driving it so it is fully warmed up, etc., there was a fan motor (I thought was the radiator fan possibly?) that would come on for about 10 seconds after you shut off the car, that no longer is coming on either.  Any chance they are related?  I'm out of ideas at this point.  Also it has been really hot and humid here in South Florida, the garage feels like a sauna, even in the morning.  I know the SAI's only operate at a certain temperature right?  Does anyone know what that temperature is?  I would guess the garage was over 80° this morning when I noticed they were not on.  Also when I had Durametric hooked up I saw that under readiness the SAI had a showed it had passes the test.

Edited June 5, 2018 by cfiiman

[Loren]

Quote

From the Porsche Cayenne Technik Book (2003-2004)

 

2665 Secondary Air System
The V8 engines in the Cayenne have separate secondary air systems for the left and right cylinder bank, mounted at the rear of the appropriate cylinder head. The secondary air blower for banks 1 and 2 are activated through relays by the DME control module. This builds up pressure over the connecting hoses up to the secondary air valves. At about 80 mbar delivery pressure from the blower, the diaphragm in the secondary air valves is opened; as a result, the injected secondary air arrives behind the exhaust valves through the distribution pipe in the appropriate cylinder head. The injection of secondary air after the exhaust valves results in a reduction of CO and HC, which are generated in greater amounts in the cold start phase with lambda < 1.

Additionally, the catalytic converters reach their light-off temperature of about 350 °C as a result of the heat released during afterburning. During the first cold start, the condition for air injection is reached when coolant temperature is between – 10 °C and 30 °C. In the range close to idle, secondary air injection runs for up to about 100 seconds, at part throttle this is reduced to about 40 seconds. If the inducted volume of air of about 340 kg/h is exceeded during secondary air injection, secondary air injection is switched off. A  supplementary non-return valve is integrated in the secondary air valve of the Cayenne Turbo, which prevents opening as the result of pressure spikes in the exhaust system.

End stage diagnostics monitors the relays, the operation of the secondary air system is monitored by closed loop O2 sensor control.

6

 

 

[cfiiman]

1 hour ago, Loren said:

 

 

Wow, thanks Loren!  I'm thinking I possibly jumped the gun with how hot it has been in the garage.  I shut the car off at about 8pm and it was at normal operating temperature (180° or so I think?) and then sat in a hot garage (this evening it measured 88° out there) all night.  I"m thinking maybe the coolant temperature was slightly above 86° and that is why the pumps didn't come on.  I'll make sure to hook up durametrics in the morning and see what it is showing since the conditions will be similar tomorrow.  

 

Any idea on why I'm not hearing that fan/motor running right after shut off?  I know it is a totally different issue just weird happened on the same day.  I would think the heat would actually make that system definitely come on so can't use that excuse, any ideas?

[Loren]

You might be over-reacting.

I would try it a few more days and see if it continues to not come on at startup. Then start digging into the problem.

[cfiiman]

Hey Loren,

 

Just wanted to report back.  Thanks so much for the helpful info again. I think as you said, I've overreacted.  Based on the info you provided me about the DME needing to see 10-24°c, I just went out and checked the temperature in the garage this morning, it was a balmy 83°f in there. Then I hooked up Durametric and the engine temperature and intake temperature are both sitting at 39°c which is 15° over the 24°c in needs to be for the DME to activate the pumps. 

[bigbuzuki]

There is a fuse that controls both the SAI relays.

Check out fuse F12 (5 amp) in the engine bay fuse box.