Error code P0605 - PCM Read Only Memory (ROM) Error

Sometime late last year the rubber hose leading into the EGR/intake from the intercooler split, threw a CEL and went into limp mode. I replaced the split intercooler hose with the radiator hose from Carquest, as found in a how-to from this site. I also replaced all of the vacuum lines at the same time, including the one inside the computer - my third time doing this.

After doing so the car immediately returned to full power. I cleared the CEL code, but the CEL continued to come on. Things have been a little hectic this past year and the car was running fine, aside from the CEL coming on, so I didn't bother to look into it any further until this past week. Every time I have had the code cleared the CEL still comes back on, but the car seems to be running fine. The weird thing is, after I have the code cleared I start the car and drive to wherever and the CEL never comes on the whole trip. I get to my destination and shut the engine off. When I start the car for the second time the CEL comes on after 30 seconds and stays on. The cycle then repeats itself if I have the code cleared again. Any thoughts or suggestions?

Yup, examine carefully the MAP module inside the ECU for damage. A VCDS log will tell you what the ECU is reporting as boost pressure.

Before you do that, look at the vacuum line from the intercooler pipe to the ECU. I've found that they like to chafe where they go into the channel leading to the ECU.

The MAP module looks fine, and I replaced the vacuum line inside the ECU and the one leading back to the intercooler. I cleared the CEL and the same thing happened - first time running the engine it stayed off, but the second time it came on after 30 seconds. Any other suggestions?

Starting to sound like a stuck wastegate.

1) Try actuating the wastegate actuator with a bicycle pump - should start opening at 3-4psi. If not, it is probably rusted shut.

2) If rusted shut, I would lube the shaft with PB blaster or similar penetrating oil, several times over several hours, then try woring it loose with a pair of pliers.

HTH

Merry Christmas!

Tony

Is the wastegate easy to get to in order to lubricate it - from the top or from under the car?

If the wastegate were stuck would the car still run ok? I don't notice any power loss, and everything seems normal. The only thing I have noticed over the past few years is that it is really loud and runs a little rough for a few minutes when I start it first thing on a really cold morning - cold in NC is in the 30-40's. On a warm day it starts and sounds just fine. I attributed this to being an old car, but who knows?? To me, it seems if the wastegate were getting stuck it would affect the engine performance, but what do I know.

I have a A3 with 136k miles and I have never replaced the N75, which I believe controls the wastegate via vacuum, right? Could that also be the culprit? When I changed the vacuum lines last year it looked like it had a lot of gunk in it so I sprayed out out with some brake cleaner. Probably not the best thing to use, but it got a lot of gunk to come out.

Marin said:

Is the wastegate easy to get to in order to lubricate it - from the top or from under the car?

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Access it under the car. Spray on the PB blaster, let it set, and then free it up with air pressure or applied force. Then lubricate it with a good synthetic spray lube. Breakfree, superlube, etc.

marin said:

I have a A3 with 136k miles and I have never replaced the N75, which I believe controls the wastegate via vacuum, right? Could that also be the culprit? When I changed the vacuum lines last year it looked like it had a lot of gunk in it so I sprayed out out with some brake cleaner. Probably not the best thing to use, but it got a lot of gunk to come out.

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If a lot of gunk came out, the N75s diaphragm is hardened and not moving like it should. It's 10 years old and tired. Replace it with a generic Pierburg unit from the vendor of your choice. ~$50. Often wakes up tired 1Z/AHU cars. I replace a bunch of these on the old iron TDIs.

To get the CEL to go off and stay off, is it more likely the stuck wastegate or the N75? Or a combination of both? I'm planning to sell the car and do not want to start dumping money into it. The car seems to run fine - the CEL is just annoying and a "red flag" to potential buyers.

Do you happen to know the part number for the N75 and cheapest place to purchase it?

Thanks for all the input!

Marin said:

I'm planning to sell the car and do not want to start dumping money into it. The car seems to run fine - the CEL is just annoying and a "red flag" to potential buyers.

Do you happen to know the part number for the N75 and cheapest place to purchase it?

Thanks for all the input!

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I feel so......used

http://metalmanparts.com/product.sc?productId=87&categoryId=18

LOL! Believe me...I will surely miss "Ruby". She has been a great car and I would consider keeping her if she had more safety features, but I've had a few too many near-death experiences due to no ABS, no DSC, etc... With three kids and a wife to transport around and to care for it's just not worth it.

Don't feel too bad though because I am upgrading to a newer TDI - not sure which one just yet.

So, do you think I should replace the N75, or just start with the possible sticky wastegate? Or both?

I don;t think it is N75 or wastegate .
If you have problem with N75 or wastegate you will have problem with power. You will loose power during acceleration. As I understand you don't have this problem.
I had same code on my and one more car. I just did replace vacuum hose inside ECU and one goes from boost pipe to ECU. If you have to soft hose or to big diameter hose you will have same problem again and I think this is your only problem. Also make sure you put clamps back on hose on inside ECU one.

Correct, I am not having a problem with power.

I did use a thick walled hose when I replaced the vacuum line from the intercooler pipe to the ECU and inside the ECU. I can't see why that would make a difference, but I guess I could swap it out for a thinner wall hose. I also do not have any clamps on the hoses, so I'll try that too. Thanks!

I am having a p0605 code on my 97 Jetta. I have replaced all of the vacuum lines since, except for the small one in the ECM and the blue one from the N75 (does that go to the turbo?) I used some generic rubber hose from AutoZone, it fits snug and stays on, but I am probably going to order the silicone lines and do it again soon.

I am experiencing a bit of power loss, it seems, and definitely a drop in Fule Mileage, from about 48 to 38, avg. I am in SoCal, so it's a warm enough climate that I should lose efficiency from warming up or anything like that. Does anyone have any suggestions? How exactly do I check the wastegate? Can I use a brake bleeder in lieu of a bike pump? Where is it, and what am I looking for in the check?

The CEL is usually on, but I've had a few occasions where it didn't come on for about 45 mins, so I think if it were a vacuum line, it would be more consistant. Maybe the wastegate frees itself up periodically? My N75 clicks constantly, not sure if that's good, bad or not significant.

Thanks

You have to replace one in ECU to get rid of code po605.
Be careful when you do that to not brake little plastic pipe inside ECU

Im doing that this weekend, but is it likely that that is causing my MPG loss, or would that be symptom of something more significant? Lots of other posts about the P0605 code mention no MPG loss.

Thanks for responding...btw, does anyone know the Torx size for the ECM ofhand?

Po605

ClemXP said:

Im doing that this weekend, but is it likely that that is causing my MPG loss, or would that be symptom of something more significant? Lots of other posts about the P0605 code mention no MPG loss.

Thanks for responding...btw, does anyone know the Torx size for the ECM ofhand?

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im on my second ecu the first replacement got rid of the problem and now some years later the new one is throwing the sane po605 code, ive checked the waste gate (no power loss) and all hoses were replaced with wurth hose,are you saying that the ecu needs to come apart and look for a vac leak inside?

gfinn said:

im on my second ecu the first replacement got rid of the problem and now some years later the new one is throwing the sane po605 code, ive checked the waste gate (no power loss) and all hoses were replaced with wurth hose,are you saying that the ecu needs to come apart and look for a vac leak inside?

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Yes , you have to open ECU and there is a vacuum hose inside ECU.

Hi Gents, TDI times 2 chick here. I have 98 TDI and the engine check light came on a few months back. The shop said it's the ECU, I say; not so fast. I purchased a Can OBDII and got an error code P0605. I pulled the ECU out of it's tray and checked the vacuum line as discussed on this forum. Its a fabric type hose with no clamp at the ECU but clamped at the other end. I check it out and it is playable and doesn't look bad but it's hard to confirm with the naked eye. The car runs great with over 250k on it but this line has never been replaced. Any thoughts?

Don't shoot me

You are going to tell me to replace the V hose within the ECU right? I was looking at the like going to the ECU and it looks ok. So I am assuming that I have to pop the cover off the ECU to gain access to the hose within correct?

aeropro said:

So I am assuming that I have to pop the cover off the ECU to gain access to the hose within correct?

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Yup!

Tony