2002 Passat TDI 130 - N75 Valve / ECU Problem

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Wed 7 Sep 2011 12:57
2002 Passat TDI 130 - N75 Valve / ECU Problem - kder

1. Checked for vacuum at the N75 vac side - 25inhg, no vacuum on out side.

2. Replaced N75 with new valve but still not operating.

3. Checked wiring to N75 valve. Measured resistance and voltage drop from N75 valve plug to ECU plug - all fine.

4. Jumped N75 valve plug power side and set up other terminal to vechicle earth - N75 valve operates fine with manual earth. Good vacuum on out side and turbo actuator operates.

The fault seems to be in the ECU. Is there any other checks I need to perform?

Any other ideas?

Thanks.

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Wed 7 Sep 2011 13:59
2002 Passat TDI 130 - N75 Valve / ECU Problem - Peter D

Do you know if your cruise control is working. Why you may ask, If the brake switch has failed or the clutch switch the Diesel direct injection system control unit J248 shuts the turbo down. The brake switch has two poles, one for the brake light and a normally closed contacts for J248 and the ABS unit. If you would like the diagrams PM me or post up your email address and I'll send them. A diagnostic code read will point to the problem. Regards Peter

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Wed 7 Sep 2011 14:41
2002 Passat TDI 130 - N75 Valve / ECU Problem - kder

Hi,

Thanks for your reply. Car does not have cruise control. Does this make a difference?

So are you saying if either of the switches you mentioned is faulty the ECU or J248 stops the operation of the N75 valve?

I will try and check the switches to see if they are ok. I think I have the wiring diagrams but if not will get back to you. I have ordered VAG-COM cable and VCDS-lite software from ebay so hopefully I can read the codes.

Edited by kder on 07/09/2011 at 14:42

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Wed 7 Sep 2011 22:28
2002 Passat TDI 130 - N75 Valve / ECU Problem - Railroad.

Kder. I have the full version of VCDS, and you can use that for output tests that include the N75 valve which can be easily activated and checked. The same can be done for the N18 valve for EGR, as well as others too. I don't know if VCDS-lite supports this function though.

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Fri 9 Sep 2011 10:57
2002 Passat TDI 130 - N75 Valve / ECU Problem - kder

Ran VCDS-Lite and the following code was displayed

1 Fault Found:

17564 - Manifold Pressure Sensor (G71): Open/Short to Ground

P1156 - 35-10 - - - Intermittent

Cleared the code a few times but it reappeared immediately. Do I need to replace this sensor or should I check the wiring also?

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Fri 9 Sep 2011 11:10
2002 Passat TDI 130 - N75 Valve / ECU Problem - Peter D

PM me or post your email address in your thread and when you have received the diagostic pages for this sensor you can edit your post and remove the address. Regards Peter

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Fri 9 Sep 2011 12:01
2002 Passat TDI 130 - N75 Valve / ECU Problem - kder

Hi Peter,

email - removed at poster's request.

Thanks for your help.

Edited by Avant on 11/09/2011 at 21:36

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Fri 9 Sep 2011 12:32
2002 Passat TDI 130 - N75 Valve / ECU Problem - kder

edited

Edited by kder on 09/09/2011 at 12:32

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Fri 9 Sep 2011 15:47
2002 Passat TDI 130 - N75 Valve / ECU Problem - Peter D

It looks as though you missed the edit window. Ask the moderator to remove your email address. Regards Peter

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Fri 9 Sep 2011 17:35
2002 Passat TDI 130 - N75 Valve / ECU Problem - craig-pd130

At least the MAP sensor is easy to get at on the B5.5 Passats ... it might be worth using some switch cleaner on the loom connector, and gently removing the sensor and cleaning that with switch cleaner too.

The sensor can get coated in soot and oil over time. If it's still throwing a code, then replace.

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Fri 9 Sep 2011 17:38
2002 Passat TDI 130 - N75 Valve / ECU Problem - Peter D

It's not a MAP problem it is a Manifold Pressure Sensor problem. Do try and keep up. Regards Peter

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Fri 9 Sep 2011 20:36
2002 Passat TDI 130 - N75 Valve / ECU Problem - Railroad.

Kder, assuming that VCDS-lite has the same functionality as the full version then try the following:

Plug in and open the Engine controller.

Go to Measuring Blocks.

Go to Group 11

The 2nd and 3rd field show expected MAP and actual MAP.

Open a log and save to a location on your PC. It will save as an .xls file.

Take the car for a drive and give it full throttle when possible.

When you get home open VC-Scope. Locate the file you saved and the video will play back on a graph. You will see how the actual MAP compares to what the ECM is expecting.

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Fri 9 Sep 2011 21:31
2002 Passat TDI 130 - N75 Valve / ECU Problem - craig-pd130

MAP = Manifold Absolute Pressure sensor. I am keeping up, thanks -- maybe check your glasses? Regards, Craig

Edited by craig-pd130 on 09/09/2011 at 21:36

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Fri 9 Sep 2011 22:22
2002 Passat TDI 130 - N75 Valve / ECU Problem - 659FBE

Manifold absolute pressure it certainly is, but to set the record completely straight, the same Bosch unit also measures charge air temperature. As the charge density is a function of both, the dual measurement is essential to allow the correct fuel delivery to be computed.

These Bosch transducers are generally reliable - and very easy to change.

659.

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Wed 14 Sep 2011 00:46
2002 Passat TDI 130 - N75 Valve / ECU Problem - kder

Just to follow up - the MAP sensor seems to have solved the problem. Thanks for the help.

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Wed 14 Sep 2011 10:01
2002 Passat TDI 130 - N75 Valve / ECU Problem - craig-pd130

Good stuff, hope it's a permanent fix.

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