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So after my 03 Passat 1.8t sat for a year I tried to start it and the oil light flashed stop immediately, my tach jumped all over the place and relays clicked like crazy all without starting and running. I opened the trunk with the key and tried again and it fired right up. It seemed alright for a week besides the tach occasionally not moving at all or jumping around even when idling smooth. I started it every day for a month but never drove it while I waited for tags and every day it ran better. I got my tags replaced the fuel filter and went on her maiden voyage and on this 11mile trip the idle became strange and my afr would occasionally hit 22.5 and my vacuum would read 15in/hg so I checked for loose coupler or broken vacuum lines to no avail. I pulled my ecu cover and noticed corrosion on the big 40 amp fuse so I pulled it to clean it and the ecu has not had power since. The fuse is fine I’ve gotten new relays cleaned every connection with corrosion but am at a total loss.
 

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1998 Passat GLS Wagon AEB , 2003 Ford Ranger Edge
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So after my 03 Passat 1.8t sat for a year I tried to start it and the oil light flashed stop immediately, my tach jumped all over the place and relays clicked like crazy all without starting and running. I opened the trunk with the key and tried again and it fired right up. It seemed alright for a week besides the tach occasionally not moving at all or jumping around even when idling smooth. I started it every day for a month but never drove it while I waited for tags and every day it ran better. I got my tags replaced the fuel filter and went on her maiden voyage and on this 11mile trip the idle became strange and my afr would occasionally hit 22.5 and my vacuum would read 15in/hg so I checked for loose coupler or broken vacuum lines to no avail. I pulled my ecu cover and noticed corrosion on the big 40 amp fuse so I pulled it to clean it and the ecu has not had power since. The fuse is fine I’ve gotten new relays cleaned every connection with corrosion but am at a total loss.
When it sat for a year was it outside in the elements? What is the climate like in your area? With the tach jumping around and then not makes me think of the crankshaft position sensor. It could be something as simple as there is some water in the connection itself creating your vacuum/boost leak like condition. Have you measured the resistance on the CPS harness side. I believe it's pins 1 and 2 and should test between 700-1300ohms. When you say the ECU hasnt seen power since, does that mean you checked for voltage? How old is the battery, you could have 12.5volts but without enough current its fruitless. I think battery because of oil light and multiple relay clicking you heard. Then there's the trunk thing you mentioned, like the hood it has a switch for the alarm. Have you pulled up the driver's carpet to look for water? Do you have a sunroof?

I know my questions are all over the place, it doesn't look any better in my head. Its already 4am!!
 

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Discussion Starter · #3 · (Edited by Moderator)
Hey thanks for the reply. So I replaced my crank position sensor also with oem Volkswagen part, and the code I’m getting is 17609 open circuit to ecm. The ccm had 0 moisture in the box or atleast no evidence water had pooled in there. I live in va and it had been under a tree and fairly rainy so I know water got to my relays they were all a little corroded and the thermo fuses were completely covered in corrosion. Also I took the metal case off my ecu for examination and there was quite a bit of corrosion on the 6 large pins on the left side of it cleaned it with wurth circuit cleaner and have still had no change.
 

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1998 Passat GLS Wagon AEB , 2003 Ford Ranger Edge
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Also I checked voltage below the ecm relay and it was 12 volts, I replaced that relay and still have the open circuit code.
No problem, cant always guarantee I have an answer, but can guarantee plenty of questions.

It sounds like you've isolated the circuit. Have you tried removing the relay and putting a jumper between where pin 30 and pin 87 would be and trying to start? Have you checked continuity on the signal wire from the ECU to relay? Don't have my Bentley on me so can't recall which pin it is on the ECU. Also how do the two ground points above the lower a pillar coupling station look?

Im just hoping for the best and the ECU isn't fried. It's amazing what a tiny bit of water can do, that's why I keep a ridiculous amount of dielectric grease in the toolbox. Btw how does the gasket look on the ECU box, not the lid seal but the bottom of the box to body.
 

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17609P1201Cyl.1-Fuel Inj.Circ. Electrical Malfunction
See this list: VW Online Technical Library - Diagnostic Trouble Codes (DTC) Tables

The ECM/ECU Relay only activates while the engine is cranking or running.

You will need to find, and repair or replace all corroded connections.
With corrosion that bad and in so many places, there is no guaranty that you will ever be able to find and fix all of them.
 

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So the mystery has been solved, it was corrosion in the harness below the relay for the ecm and also a bad crank position sensor
Congrats. Now lather them connections up with dielectric grease. Always keep a spare CPS on hand.

I’m not very good with a volt meter I’m not sure how to check continuity. But fuse 29 is getting power and I can smell fuel when I crank it.
When I was saying to check resistance on the CPS you would switch the multimeter to the greek Omega symbol, some multimeters have specific ranges you need to switch it to depending on what you are looking for, but most digital multimeters will have an auto setting. So Resistance is just that, a measurement of resistance to the flow of current. Like if you stepped on a hose you are creating resistance to the flow of water. In this case, you are just testing for an ohm range based on the component's specifications. Continuity on the other hand you don't want any resistance. 0 to 50ohms is ok that's just residual, what you want to see is OL (Open Loop) most people call it infinite loop. Now if you had a high reading of ohm/resistance then you know you have a short in that circuit.

I always recommend to people to buy and learn how to use a multimeter. They are intimidating at first, and never be afraid to ask. People on here are like Tom, PZ, Vagguy etc are knowledgable and good people. This isn't VWVortex. It's just incredibly important in diagnostics. See how you didn't even get a CPS/Engine Speed Sensor/G28 trouble code? OBD diagnostics are great, but a lot of the time it just gives you some clues to the riddle.
 

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I’m not very good with a volt meter I’m not sure how to check continuity. But fuse 29 is getting power and I can smell fuel when I crank it.
There's a book on Amazon, Everything Electrical, how to use a voltmeter. It costs like $16.00 It goes over all voltmeter functions. If you are unsure how to use a voltmeter properly, it is an invaluable reference to have around.
 
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