2000 VW Cabrio: OBD-II codes mostly ground circuits

[Hiramhaus]

I have a 2000 Cabrio MK3.5. I had a fuel delivery problem. Initially when you revved it up it was missing at higher RPMs. Since I had this happen in my MK1 recently I replaced the Fuel Pump Relay (I know its hard to get the right one) and the Fuel Pump itself. I had gone to autozone the minute the check engine light came on and they said there were no codes. Thats why I dove into the fuel delivery system.

That was a "parts changer" response. The problem was gone for a minute, then returned a day later. So, I broke down and bought a modest OBD-II code checker. I got 12 codes.

I found that I have
1) Cyl1 open to ground
2) Cyl2 circuit open
3) Cyl3 open to ground
4) Cyl4 Circuit open
5) Air Pump open to ground
6) Low voltage on my Mass Air Flow Sensor (which I have taken out an 7) cleaned)
EVAP system open to ground
9) Tank vent valve - open to ground

There were twelve in total - when I remember the others I"ll add them to this list. I am suspecting that either the grounds under the battery, the wires running to the firewall, or the Fuel Pump Relay may still be the wrong unit.

Does anyone else have a suggestion - I plan on diving in after work today. I am hoping I do not have a melted harness somewhere causing this to happen. I am an air cooled person - so this is all super annoying to me, especially after I "parts changered" about $400 bucks in stuff that it appears was probably fine.

https://www.instagram.com/p/BZrz1FJHfEr/?hl=en

-Mike
_________________
1969 Ghia
2016 Audi Q3

[Butcher]

May I suggest you post the codes too. The information you have given may be related to the fuel injector or coil. The EVAP system has many components so that explanation that the system is 'open to ground' means nothing.

Do you have a wiring diagram? Bentley? Anything?

[TDCTDI]

Check for loose or broken braided ground strap from back of cylinder head to ignition coil pack.
_________________
Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.


GOFUNDYOURSELF, quit asking everyone to do it for you!


An air cooled VW will make you a hoarder.


Do something, anything, to your project every day, and you will eventually complete it.

[Hiramhaus]

Thanks Butcher and TDCTDI for the input I will look for that braided wire when I get off work. I was planning on looking under the battery, under the drip tray and inspecting the fuse box where the 409 plugs in. I hope I have the "right" 409 on my MK1 it took three tries to get the correct one for my car. I don't know what the ones that lead with a zero are as my list I can find starts with P1XXX

https://www.obd-codes.com/trouble_codes/volkswagen/


P0102

P1237 Injector Circuit Open Cylinder 1

P1226 Injector Circuit Cylinder 2 Short To Ground

P1227 Injector Circuit Cylinder 3 Short To Ground

P1240 Injector Circuit Open Cylinder 4

P1451 Secondary Air Injection Circuit Short To Ground

P1421 Secondary Air Injection Valve Circuit Short To Ground

P1425 Tank Ventilation Valve Short To Ground

P1472 EVAP Control System LDP Circuit Short To Ground

P0300 ?(handwriting problem)

P1500 Fuel Pump Relay Electrical Circuit Malfunction

P0411 ?(handwriting problem?)

P1146 ?(Mass Air Flow Sensor Supply Voltage)


So far I have replaced the Fuel Pump for fun, and the Fuel Pump relay with the seven pin 409 relay. I have the fuel filter on hand but have not installed it. At times it seemed "something smelled hot" but the exhaust smells quite unusual to me.


_________________
1969 Ghia
2016 Audi Q3

[TDCTDI]

If I remember correctly, most of those consumers are on the same circuit, just one of those failing will cause all of the sensors to throw a short to ground fault.

Also, I believe that the O2 sensor heater elements are on that same circuit, unplug both O2 sensors, clear the codes, start the car & see if you still get all of the short to ground codes or if you now only get O2 sensor faults. If you only get O2 sensor faults, then one of the O2 sensors is bad.
_________________
Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.


GOFUNDYOURSELF, quit asking everyone to do it for you!


An air cooled VW will make you a hoarder.


Do something, anything, to your project every day, and you will eventually complete it.

[Hiramhaus]

I found the ground strap going to the firewall and it looks good. I went under the battery tray and the grounds are barely green but I'm going take them off to clean them tomorrow.

I'm new to having a OBD II tester. So I may have goofed it up. I cleared the codes... Then thought why not check and see... Who knows about the previous owner can the codes ride along for years after fixed?

. And then ran it around the block it choked and stumbled as expected kind of idle, skips quite a bit then sucks air when giving it gas, but... When I checked... No codes... How far do I have to drive to get them back.

I checked every fuse under dash and hood. All good there.

I never got to the 02 sensors

Did I do something terrible?
_________________
1969 Ghia
2016 Audi Q3

[Butcher]

The fuel injector has a constant power and the ground signal is controlled by the ECU. What I've found is that if you have a short to ground code, you may not have power to that circuit.

The fuel injectors should have power when the key is on, that power actually goes thru the injector windings and out the wire that gets shorted by the ECU. If there is no power to the injector, the ECU does not see that and will interpret that signal is shorted to ground.

I may not be explaining this properly, I know what I'm thinking but sometimes the words do not get typed right. What I'm saying is to check the power supply to all those circuits since most of those codes are ground codes and most of those are grounded by the ECU. If the ECU does not see a small voltage on that wire, it assumes it's shorted to ground.

[TDCTDI]

This is a possibility but the fact that the car runs leads me to believe that these consumers are getting power.
_________________
Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.


GOFUNDYOURSELF, quit asking everyone to do it for you!


An air cooled VW will make you a hoarder.


Do something, anything, to your project every day, and you will eventually complete it.

[Hiramhaus]

Unplugged both O2 sensors. No codes but P0341

Camshaft position sensor

Still ran, almost a little better. Plugged them in same code.
_________________
1969 Ghia
2016 Audi Q3

[TDCTDI]

Camshaft position sensor is the distributor, if the car runs the its probable that someone didn't get the distributor timing right when the last T-belt was done. Intermittent cutting off might be due to bad hall sensor in distributor but they are generally a good/no good scenario, not an intermittent one.

Check to see if the plug connection at the distributor is loose/hanging (CAREFULLY) the wires can sometimes ground to the housing if the connection is hanging. If it is loose/hanging, make sure to epoxy & zip tie it back to the distributor. Also be sure that the wires in the distributor won't get snagged by the trigger wheel or you will buy another distributor.
_________________
Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.


GOFUNDYOURSELF, quit asking everyone to do it for you!


An air cooled VW will make you a hoarder.


Do something, anything, to your project every day, and you will eventually complete it.

[Hiramhaus]

Those wires look brand new and they have a plastic loom cover over them - seem very much intact. I unplugged the distributor / hall sensor plug and the contacts look good (three of them) and then connected it back up.

Its like when you rev it up it stutters, when its going it sounds good,

zzzoooo cut cut zoooooo cut cut cut cut zooooooooooom

then a normal rev with maybe a few cutting like that.

At its worst - it wouldn't start and had ZERO power going uphill etc.... too much gas and it would shut down....

_________________
1969 Ghia
2016 Audi Q3

[TDCTDI]

Check cam/crank/intermediate shaft timing. The cam position is determined by the intermediate shaft/distributor, not the cam.
_________________
Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.


GOFUNDYOURSELF, quit asking everyone to do it for you!


An air cooled VW will make you a hoarder.


Do something, anything, to your project every day, and you will eventually complete it.