Coolant Fan Control 2: P1662 - 35-00 - Short to ground (VCDS Fault Code)

[kareems]

Hey

as the title mentions, I am getting this error in VCDS and I can't seem to find out what the problem is

 

For added context:

I had some trouble with the fans a few months ago, changed both fans (new large one and a used small one) and had the fan control module checked (the box thingy) and I have been told that It's working fine

But the error is still there and I am not sure how to approach the problem nor was I able to find diagrams for the fans wiring or anything

also is it a catastrophic fault code or can I just ignore it?

since everything seems to work fine for me 

 

I would really appreciate it if anyone can guide/direct me on how to get rid of this fault code or which parts should I check

[makymak]

I have the very same problem with my 1.6l Octy. Never found a solution no matter how much I searched it. No documentation, either. I tried different fan control modules but the problem persisted. The fans are working ok so the problem is somewhere else. If not fixed, the fans will only run at the low speed. This never gave me an overheating problem even with the A/C on at the hot summer days we have here. 

 

If you find the solution, please let me know!!! 

[Breezy_Pete]

I had a look at wiring diagrams, and on AVU with the basic A/C there are two command wires from engine ECU to fan control module.

There's a connector in the scuttle area where these pass through.

I suspect one of these wires, or its connections (which commands full speed fan activity) may have a problem.

Details with wire colours and pin numbers at each point to follow when I get a chance.

 

 

 

[Breezy_Pete]

The scuttle connector is a green 10-way.

Pin 6 carries a yellow wire from ECU pin 77 to fan control module pin 11 (of 14-way). I think this one is probably low speed command.

 

Pin 7 carries a yellow/red wire originating at ECU pin 79 and going to fan control module pin 7.

This is the one I suspect may have a problem. If it were mine I would check that yellow/red visually and then electrically for short and open circuit.

[makymak]

Thank you, Pete! I was hoping to see you here! Your help is always useful and accurate. I will check it and report. I will try first pin 7 on the control module, maybe tomorrow, as the access is very easy. But I have to wait for the holidays to go to get into the scuttle connections as it needs some working. 

 

Hope it's not the ecu itself that is short-circuited.

[kareems]

3 hours ago, makymak said:

I have the very same problem with my 1.6l Octy. Never found a solution no matter how much I searched it. No documentation, either. I tried different fan control modules but the problem persisted. The fans are working ok so the problem is somewhere else. If not fixed, the fans will only run at the low speed. This never gave me an overheating problem even with the A/C on at the hot summer days we have here. 

 

If you find the solution, please let me know!!! 

 

1.6L octy here too and last I checked my fans were running both speeds high and low, but now you are making me a bit hesitant and I will have to double check if it works on low speed and I never had an overheating problem either

but I think that's worth mentioning, running low speed only was actually the problem I mentioned having a couple of months ago and I went to some local workshop to have the wiring inspected and the problem was fixed (supposedly?)

 

 

3 hours ago, Breezy_Pete said:

I had a look at wiring diagrams, and on AVU with the basic A/C there are two command wires from engine ECU to fan control module.

There's a connector in the scuttle area where these pass through.

I suspect one of these wires, or its connections (which commands full speed fan activity) may have a problem.

Details with wire colours and pin numbers at each point to follow when I get a chance.

 

 

 

 

3 hours ago, Breezy_Pete said:

The scuttle connector is a green 10-way.

Pin 6 carries a yellow wire from ECU pin 77 to fan control module pin 11 (of 14-way). I think this one is probably low speed command.

 

Pin 7 carries a yellow/red wire originating at ECU pin 79 and going to fan control module pin 7.

This is the one I suspect may have a problem. If it were mine I would check that yellow/red visually and then electrically for short and open circuit.

First of all, As makymak mentioned I have the same impression about your help being super accurate according to a previous thread I had here asking for help so Thanks a million Pete!!

Second, I am new to the whole DIY car fixing thing and English isn't my main language so I struggle with some terms so please correct me if I didn't get you 100% right.

What I understood is that I should remove the scuttle panel (which is the black panel under the windshield wipers shown in the photo, right? had to google that lol)

under the scuttle panel I will find the ECU with it's connectors connected and wires wrapped in some black tape/tubing, are these the wirings I should inspect for damage?

I am not really sure what the "scuttle connector" is to be honest, but my best guess is that it's the one held in this photo (since it looks green to me):

the next step, after I identify the scuttle connector, is to inspect both wires, the yellow one and the yellow/red one, from the back of the connector for any visible damage and examine them electrically through pin 6 & 7 in the connector it self

Is that right?

and what's the array for the pins in the connector? pin 1 is the one on top left side and I go on horizontally from there for 6&7?

and also by testing them electrically you mean by a 12V test light right?

Edited 26 December, 2023 by kareems

[Breezy_Pete]

The connector I mentioned has only 10 positions for wires, and is green.

I can't remember what location the circuits suggested, but I think close to the ECU.

Because there are only 10 positions, and the wires are quite bright colours, I think it will be easy to see which are the correct ones.

 

 

My understanding is that there will be one wire of each colour going from ECU to green connector and then a continuation of each from the mating half of the green connector onward to the fan control module.

I will try to find additional info and images tomorrow. 

 

Since the fault code refers to "fan control 2" I think it will relate to full speed, not low speed, so probably very rarely, if ever, needed.

 

 

[kareems]

2 minutes ago, Breezy_Pete said:

The connector I mentioned has only 10 positions for wires, and is green.

I can't remember what location the circuits suggested, but I think close to the ECU.

Because there are only 10 positions, and the wires are quite bright colours, I think it will be easy to see which are the correct ones.

 

 

My understanding is that there will be one wire of each colour going from ECU to green connector and then a continuation of each from the mating half of the green connector onward to the fan control module.

I will try to find additional info and images tomorrow. 

 

Since the fault code refers to "fan control 2" I think it will relate to full speed, not low speed, so probably very rarely, if ever, needed.

 

 

Okay the description clears it a bit, now I understood that the connector is something different from the ECU plug I referred to earlier with bright colored wires, will search for that and report back!

would it be possible that the fans work at full speed although I am having this error?

since, if I am not wrong, I remember that I tested the fans out and they were working at both high and low speed normally as far as I understand

and I would definitely appreciate any additional info/images.

[Breezy_Pete]

I don't know exactly what this fault code represents in terms of function. Just guessing that high/full speed may be affected as this would be least obvious in normal use.

How did you test full and low speed,  and when?

[makymak]

First of all, this setup is very rare among the VW group. The majority of the family cars use a two stage temperature sensor (more correctly, a two stage switch) on the radiator and this sensor is feeding the respective module (which is quite plain) 

 

Our car has an analog temperature sensor which is feeding directly the ecu and the ecu is giving the orders to the module to operate the fans. 

 

If I remember correctly, to test this kind of setup, you need to heat up the sensor or to simulate it's region of resistance (it's a simple thermistor). 

 

The control module has all the circuitry, including the fan relays. If you want to test only the fans you need to bypass the module. It's not very difficult, each fan has three wires, one for positive low speed, one for positive high speed and one ground. Furthermore, each speed is protected from different fuses in the fuse box. 

 

The green scuttle connector I guess is under the scuttle panel, protected by a waterproof cover. At my left hand drive Octy it is under the wipers motor (I learned that when I retrofitted the cruise control). 

 

If you are concerned about overheating, you can hardwire the low and high speed so it always runs the fans at high speed. Too noisy, I'm afraid. 

 

Do remember that if the problem comes to coolant fan control 1 (the low speed), the A/C also won't run, as a prevention measure. 

[kareems]

39 minutes ago, Breezy_Pete said:

I don't know exactly what this fault code represents in terms of function. Just guessing that high/full speed may be affected as this would be least obvious in normal use.

How did you test full and low speed,  and when?

for testing the fan speeds:

I turned on the ignition and waited until the car temp increased then noticed the fans turning on at a low speed

for high speed I kept the ignition on and alternated between waiting/pressing the gas pedal until I noticed that the fans' speed increased so I suppose that means high speed is working right?

16 minutes ago, makymak said:

The control module has all the circuitry, including the fan relays. If you want to test only the fans you need to bypass the module. It's not very difficult, each fan has three wires, one for positive low speed, one for positive high speed and one ground. Furthermore, each speed is protected from different fuses in the fuse box.

totally right, I tested the fans like this when I was making sure that the problem wasn't in the fans 

20 minutes ago, makymak said:

The green scuttle connector I guess is under the scuttle panel, protected by a waterproof cover. At my left hand drive Octy it is under the wipers motor (I learned that when I retrofitted the cruise control). 

 

If you are concerned about overheating, you can hardwire the low and high speed so it always runs the fans at high speed. Too noisy, I'm afraid. 

 

Do remember that if the problem comes to coolant fan control 1 (the low speed), the A/C also won't run, as a prevention measure. 

If you are planning to check the connector asap I would appreciate if you added some visual guidance with photos/videos it would help a lot and thanks for mentioning that it's under the wipers motor

I tried hardwiring the fans too when the fans didn't work properly back then and definitely noisy, sounds like you are driving a tractor 

and my AC works fine so I am not sure what I am missing here but definitely giving Pete's instruction a go since that's the only wiring I didn't check when I was investigating the fans problem earlier

[makymak]

I won't be able to check the scuttle connections before new year comes. If you search for retrofitting cruise control on vw golf mk4 you will find where these connections are. When I find some time I will post here some photos. 

[kareems]

13 minutes ago, makymak said:

I won't be able to check the scuttle connections before new year comes. If you search for retrofitting cruise control on vw golf mk4 you will find where these connections are. When I find some time I will post here some photos. 

will make sure to update the thread here if I checked mine earlier 

but I did some searching as you suggested and I guess you are referring to this:

in our case, according to Pete we should find a green connector with 10 positions for wires

 

[makymak]

Yes, that's what I meen. Strange that there isn't any green connector. Maybe the connector is somewhere else. I don't remember anymore if there was a green plug on my car.

[makymak]

Too possible the connection is not there. There are the plugs for the harness that goes into the cabin. The green plug Pete is referring to should not be in a harness that goes into the cabin. It must be somewhere else. 

[Breezy_Pete]

Green connector apparently lives in position A of this image:

 

I think that matches with an empty position in the above from the Golf video. Different engine in the Golf maybe?

 

Edited 27 December, 2023 by Breezy_Pete

[makymak]

Thank you, again, Pete! 

 

I measured pin 7 on the module plug and no short-circuit found. 

 

I quit!!! 

[kareems]

9 hours ago, Breezy_Pete said:

Green connector apparently lives in position A of this image:

 

I think that matches with an empty position in the above from the Golf video. Different engine in the Golf maybe?

 

So I suppose overlaying that diagram with the one from the golf video it should look something like this:

 

8 hours ago, makymak said:

Thank you, again, Pete! 

 

I measured pin 7 on the module plug and no short-circuit found. 

 

I quit!!! 

that's a bummer! Did you find the green connector at the place mentioned?

Will try to check mine ASAP and update you with my findings

[Breezy_Pete]

Yes, good sketch.

I would also check for continuity from fan control module to that green plug/socket pair, and from the ECU to there also. (Not just short circuit to earth; fault codes can be misleading in their wording sometimes)

Not sure which part of the loom goes to which, but if you leave green plugs mated, you can probably probe into the cable entry at that point.

Pin numbers at ECU and FCM are in an earlier post, above.

 

 

[makymak]

12 hours ago, makymak said:

 

I quit!!! 

Obviously, I'm kidding! I will remove the scuttle panel as long as I find some free time, definitely not earlier than next week. 

 

@kareemsyour findings are welcomed!!! 

[kareems]

Couldn’t wait much longer, had the wiring checked yesterday

This is the connector pete was referring to:

I checked the wiring from the ECU to this green connector I am holding in my hand using an avometer and both of the yellow and yellow/red wire gave a reading on the avometer

I also checked the wiring from the other end of the green connector to the fan control relay and both wires gave a reading also

That was a huge disappointment to me to be honest.

Currently I am intending on trying another set of fans and another fan control relay

But I am wondering what does the last letter on the fan relay refer for?

Mine has a K on it and I read somewhere that octys with wire throttle (like mine) use a relay with an L on it while the K relays correspond to octys with cable throttle but I can’t seem to find any info on the differences between different relays if there is any

and I can’t make sure if the previous car owner had it swapped

[Breezy_Pete]

Message me with the VIN of the car please @kareems, and I can check which part number it should have.

 

[makymak]

My findings are the same as @kareems

No short to ground, no discontinue from ecu to fan control module. 

 

If I disconnect the fan plug from the module, the ecu throws an error that the fan control 1 and 2 are either open or short to +

 

No short to ground error. I suspect the error is at the fan(s). 

 

I need further investigation. 

[kareems]

31 minutes ago, makymak said:

My findings are the same as @kareems

No short to ground, no discontinue from ecu to fan control module. 

 

If I disconnect the fan plug from the module, the ecu throws an error that the fan control 1 and 2 are either open or short to +

 

No short to ground error. I suspect the error is at the fan(s). 

 

I need further investigation. 

I am suspecting the fans too, but to my surprise Pete confirmed my suspicions and turns out I have a wrong fan control relay (K which should be L)!

I will start by swapping the relay to an L and see what VCDS says about it. I really hope the error isn’t at the fans as I have no interest in changing them, they seem to work completely fine to me with no temperature problems

Will update you tomorrow with my findings if I managed to do the swap.

[makymak]

 @kareems

Can you please tell as the engine type of your car? Does it have climatronic or just a/c?