P1675 Porsche fault code 658 - Fault - engine purge fan

[Silver_TT]

2002 911 Turbo (US)

On a recent hot day after turning off the car I got an error on the console indicating an error with the engine purge fan. This makes sense as I understand this is activated when the engine compartment > 172 F. Hooked up the Durametric and saw the following (see 1st attachment):

P1675 Porsche fault code 658 - Fault - engine purge fan

I understand this can be a few things including the fan being broken, the temperature sensor in the engine compartment, or fuses B4 and C5 and the relay, or even a DME fault. Of these possibilities I believe my issue may be fuses B4 and C5 or the relay because when I'm in the Durametric software and I try to activate the "Engine compartment purge fan" (see 2nd attachment) it doesn't do anything. However, I tried to activate the "Fan Stage 3" as another test to be sure there wasn't a communication error and I can hear that big blower fan go on just fine as I would expect. The only strange thing is that when I try to activate the "Engine compartment purge fan" I don't get a new P1675 error after the previous code has been cleared, which I would have maybe expected.

I'm lazy, so I first decided to check the fuse box because it's the easiest to access. I popped out B4 and C5 (see 3rd attachment) and sure enough I can see that B4 is blown.

Now my only question is: Are these fuses special in any way? In other words, can I run up to AutoZone right now and buy one (I'm assuming this is a 15 amp)? Or should I wait until Monday and drive to the Porsche dealer to specifically get one from them?

[Loren]

Autozone fuses should be fine as long as they are the same type and rating.

Buy a few because if your fan is shorted it will blow again.

[Silver_TT]

Thanks. I went to AutoZone and picked up a 5-pack of Cooper Bussman 15A fuses (BP/ATC-15-RP was the part number). The AutoZone website says this is compatible with my vehicle and Cooper Bussman is a reputable company so I'm assuming they should be just fine.

However, as soon as I replaced the fuse I heard the engine compartment fan come on for less than a second, then instantly went off. Pulled the fuse and sure enough it's blown.

How should I proceed to fix the short at this point? Do I need to replace the engine compartment fan? If so do you have a part # for this and is this pretty straight-forward? I would like to get this sorted ASAP since Summer heat is rapidly approaching.

[JFP in PA]

You need to start looking for a short in the system. Disconnect the fan harness at the fan and check for a short; you can also try jumpering the fan itself to see if it runs without issue. You may also need to check the relay and temp sensor circuits for shorts as well. This is a process of elimination to find where the problem(s) lie.

[Silver_TT]

Ok. I unplugged the harness at the fan in the engine compartment, replaced the fuse with a new one, put the key in the ignition and turned to the last position before starting the motor..... and the fuse did NOT blow.

This means it must be the fan correct? Fan part is in pic attached. Made in Italy? Is this an OEM fan?

To continue driving should i leave the new fuse in with the fan harness disonnected? Or go back to the way it was with a blown fuse in there and the fan plugged in? Or it doesn't matter?

Thanks to both of you...and for such fast replies! You guys are awesome.

[Loren]

That is a Porsche part - see the Porsche trademark logo?

Replacement part is a 997 part - 997 624 046 01 Blower Fan -- US MSRP $119.85

I would leave it unplugged.

[JFP in PA]

Once the fuse pops, the circuit is dead all the way back to the power source. You can now check the fan motor itself for a internal short using a multimeter.

That looks like the OEM fan.

[Silver_TT]

Thanks, ya I saw the logo but just wanted to be sure. Saw the part# on there but wanted to be sure it hadn't been superceded -- doesn't sound like it but Sunset can answer that for me. I also saw 29/07/09 which I'm assuming is a manufacturer date -- therefore this was replaced before and this replacement really isn't that old (< 4yrs). Hopefully there's not something in the electrical system putting stress on it causing it to die early. For now I will leave it unplugged with the new, unblown fuse in the box.

JFP - I have a multimeter. Sorry for the required hand-holding but how exactly would I use it to test for the internal short at the fan as you stated?

Thanks again...if I can determine this today I can order the part from Sunset and install this week.

Edited June 15, 2013 by Silver_TT

[JFP in PA]

Thanks, ya I saw the logo but just wanted to be sure. Saw the part# on there but wanted to be sure it hadn't been superceded -- doesn't sound like it but Sunset can answer that for me. I also saw 29/07/09 which I'm assuming is a manufacturer date -- therefore this was replaced before and this replacement really isn't that old (< 4yrs). Hopefully there's not something in the electrical system putting stress on it causing it to die early. For now I will leave it unplugged with the new, unblown fuse in the box.

JFP - I have a multimeter. Sorry for the required hand-holding but how exactly would I use it to test for the internal short?

Thanks again...if I can determine this today I can order the part from Sunset and install this week.

You are almost home, but you need to confirm it is the fan itself, and not a short in the wiring leading to the fan. With a multimeter, check the fan's circuit for continuity, resistance, and a possible short to ground (the fan housing) on either leg of the fan motor's wiring connector. If the fan motor's internal circuit shows a short to ground, it is Miller Time and you need a new fan; but if there is no short, you need to check the wiring harness going to the fan for the same type of short.

[Silver_TT]

Test #1: CONTINUITY

A new fuse is in the fusebox. I have a cheap DT-830B digital multimeter. To test continuity I have plugged the black wire into COM and the red wire into VΩmA. I have the dial set to 2000k on the Ω section (see attached image which shows the settings I have configured, with the red and black not touching anything, therefore the reading is "1").

The results are as follows:

Reading of "0" when touching the 2 leads on the fan itself.

Reading of "004" when touching the 2 leads on the wiring harness that plugs into the fan.

[JFP in PA]

Test #1: CONTINUITY

A new fuse is in the fusebox. I have a cheap DT-830B digital multimeter. To test continuity I have plugged the black wire into COM and the red wire into VΩmA. I have the dial set to 2000k on the Ω section (see attached image which shows the settings I have configured, with the red and black not touching anything, therefore the reading is "1").

The results are as follows:

Reading of "0" when touching the 2 leads on the fan itself.

Reading of "004" when touching the 2 leads on the wiring harness that plugs into the fan.

You have it set too high, turn the meter down to 200 ohms, then if you touch the two meter leads together, your meter should read either "0" or some very small value near "0". If the fan is still reading "0" that means it is an open circuit with no resistance, which is highly unlikely for an electric motor. If you get a Ohm reading on the motor circuit at the lower setting, note it and then try getting a reading between each of the fan's connections and a bear metal area on the fan housing (you are looking for a short). If you get a "0" or near "0" reading between either wire and the housing, that is a short. Neither wire should indicate continuity to the fan housing.

Next try the same test on the harness that connects to the fan, check the two wires first, then each one to a chassis ground (one should be a ground, but both should not read as having continuity to ground). If both read as continuous to ground, there is a short in the harness or the relay is shorted.

[Silver_TT]

Thanks for sticking with me on this. As you can see my "greenness" is showing, but fortunately for me so is your patience/persistence.

Here are some revised results with the multimeter now down at the 200 setting in the Ω section (see image showing a "01.1" reading with the red and black leads touching each other).

REVISED READINGS on the 200 Ω setting:

Reading of "01.1" when touching the red/black leads on the fan leads.

Reading of "05.4" when touching the red/black leads on the wiring harness that plugs into the fan.

Assuming I did this correctly......Correct me if I'm wrong but does this mean the fan is ok and I need to check this same resistance at the relay now next (which I understand to be the next point as we work backwards along the series)?

Edited June 18, 2013 by Silver_TT

[JFP in PA]

Before going to check the relay, check the fan connections to the fan housing for a short to ground (you should see no continuity between either wire connection and the housing).

[Silver_TT]

hmm.. i was trying to think though this. the fan housing is mostly plastic. when I touch the red or black lead to one of the fan's leads, and then the other of the multmeter's leads to what I think is metal (like in the very center of the fan) I appear to get a "1" reading. Down in my garage looking at this closer now......

[Silver_TT]

JFP -

Regarding your last check of the fan before moving on to the relay, just to be clear I uploaded another photo. The left arrow shows the fan's two leads that I was putting one of the multimeter's leads to. The up arrow shows an area of the fan housing that is metal underneath the plastic cover. I was putting the remaining multimeter's lead to this metal. The multilmeter was reading "1". I tried both leads on the fan, and also the difference combinations of the red/black leads from the multimeter (although I don't believe it should matter and any single combination should achieve an answer to what we wanted to know doing this test).

Time to dig into my back seats to try to access the relays and check this same resistance there?

[JFP in PA]

It sounds like the fan may be OK as you do not seem to be getting continuity between the housing and the wire connections.

The #8 relay that controls the fan should be the same part number that is used to control the movable spoilers on these cars, so the easiest move may be to simply try to swap the relay and reconnect the fan and turn on the ignition to see if the fuse doesn't blow with the new relay in; if that is in fact what happens, it is the relay, which is much cheaper than a new fan.

[Silver_TT]

Trying to get the carpeted cover off behind the rear seats. I popped off the covers over the Bose speakers and see some bolts. There's a big one under each Bose speaker (see attached, circled in red). Anyone know what needs to get unscrewed to pop this off and get to the relays under there......?

I also found the following from jpflip which may be helpful to anyone else in the future (see second attachment). It was with respect to something else but gives the numbered layout of the relays.

Edited June 15, 2013 by Silver_TT

[Silver_TT]

It sounds like the fan may be OK as you do not seem to be getting continuity between the housing and the wire connections.

The #8 relay that controls the fan should be the same part number that is used to control the movable spoilers on these cars, so the easiest move may be to simply try to swap the relay and reconnect the fan and turn on the ignition to see if the fuse doesn't blow with the new relay in; if that is in fact what happens, it is the relay, which is much cheaper than a new fan.

One other thing... when I'm able to get to the relays and do the swap, assuming for the moment that the fan relay is bad, should I be plugging this into the slot that I took the relay from the spoilers? In other words if this is a bad relay, won't it blow the fuse for the spoilers too? Or would I want to try by taking the relay from the spoilers..... using that for the engine purge fan while leaving its original slot empty (not sure what electrical implications that would have but prefer not to break anything else in the process while testing). Just a thought as I'm trying to think through this.

Also, is the relay #8 I'm seeking on the driver's side or passenger's side once I'm able to get this carpeted segment off?

I know this is an awefully verbose sequence but hopefully when I'm able to solve this it helps someone else in the future that finds this thread........

Edited June 22, 2013 by Silver_TT

[JFP in PA]

It sounds like the fan may be OK as you do not seem to be getting continuity between the housing and the wire connections.

The #8 relay that controls the fan should be the same part number that is used to control the movable spoilers on these cars, so the easiest move may be to simply try to swap the relay and reconnect the fan and turn on the ignition to see if the fuse doesn't blow with the new relay in; if that is in fact what happens, it is the relay, which is much cheaper than a new fan.

One other thing... when I'm able to get to the relays and do the swap, assuming for the moment that the fan relay is bad, should I be plugging this into the slot that I took the relay from the spoilers? In other words if this is a bad relay, won't it blow the fuse for the spoilers too? Or would I want to try by taking the relay from the spoilers..... using that for the engine purge fan while leaving its original slot empty (not sure what electrical implications that would have but prefer not to break anything else in the process while testing). Just a thought as I'm trying to think through this.

Also, is the relay #8 I'm seeking on the driver's side or passenger's side once I'm able to get this carpeted segment off?

I know this is an awefully verbose sequence but hopefully when I'm able to solve this it helps something else in the future that finds this thread........

Relay panel #2 is on the driver's side of the shelf area (the engine DME should be on the other side). I totally forgot about the Bose option that requires removal of the fasteners to get the parcel trim panel up to gain access to the relays, cars without the Bose are not as complicated. Remove the two fasteners under the Bose "vents" and the shelf should slide forward.

I would pull the existing suspect #8 relay out completely and move the spoiler relay (#9) into the #8 slot and then reconnect the fan to test the circuit. If everything works OK (fuse does not pop) and the Durametric can run the engine compartment fan without issue, you will need another relay. At that point, you can move the relay back into #9 slot and just leave the engine fan relay out until you get a new one (the car will code for the missing relay), or leave the relay in the engine fan slot and live with out your spoiler until the new relay is available.

Aren't electrical diagnostics fun? :eek:

[Silver_TT]

Got the parcel trim panel off. If you have the Bose option the face plates need to come off and then you need to unscrew the large silver bolt I have circlued in red above.

Now time to swap the relay and see is the fuse blows.....

[JFP in PA]

Got the parcel trim panel off. If you have the Bose option the face plates need to come off and then you need to unscrew the large silver bolt I have circlued in red above.

Now time to swap the relay and see is the fuse blows.....

Fingers crossed..........................

[Silver_TT]

Here's the DME relays panel. Which one am I pulling out? And replacing with which one? Don't want to mess this up and fry my DME. I'm pretty sure it's one of those 3 burned orange colored ones. There's one for the engine purge fan and 2 for the spoiler.

That diagram I provided earlier from jpflip may be for the passenger side or something...the numbers don't seem to match up....???

I'm in the panel behind the driver's seat side. Is this definitely correct?

Edited June 15, 2013 by Silver_TT

[JFP in PA]

Top row, second from right is #8 (red in color), #9 (next one over to the left on top row) should be the spoiler retract relay and have the same part #.

[JFP in PA]

Here's the DME relays panel. Which one am I pulling out? And replacing with which one? Don't want to mess this up and fry my DME. I'm pretty sure it's one of those 3 burned orange colored ones. There's one for the engine purge fan and 2 for the spoiler.

That diagram I provided earlier from jpflip may be for the passenger side or something...the numbers don't seem to match up....???

I'm in the panel behind the driver's seat side. Is this definitely correct?

Jpflip has the diagram upside down for some reason (look where the maxi fuse for the air pump is in the diagram vs. your picture)............

The three red colored relays are all the same part numbers; #8 is the fan, #9 is spoiler retract, and in the bottom row #3 is spoiler extension. If you need, I can scan a photo from the manual (looks just like your photo) and post it with the relay locations.

[Silver_TT]

Shoot, no dice. Removed the relay circled in red and replaced it with the relay circled in blue (and left that one with nothing). Every time I try to activate the fan using the Durametric it blows the fuse. The short must be somewhere else. How else can I track this down? Does this just leave the wiring... or, God forbid, a problem with the DME. Electrical problems suck :)

Any ideas what I should try next? Anything else I should be doing in the relays before I put that back together?

Edited June 22, 2013 by Silver_TT