TDI Critical sensors

Hi Everyone;
Just completed a 2 week road trip which went very well.
There were some long dark roads which I would not liked to
have broken down on. This got me to thinking about which
sensors could cause a dead in the tracks car. I know the
G 28 crank sensor is one (can go out with little warning)
I have about 366,000 km on my 2000 TDI and have replaced
this sensor twice. Are there any other critical sensors (parts) like this?

Thanks
Peter

Cam sensor can cut if off in some engines. Shut off solenoid on the IP too.

A faulty ECT can cause a crank-no start


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Engine coolant temperature? Never seen that happen...

k_pt said:

Engine coolant temperature? Never seen that happen...

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The CTS (ECT) controls glow plug time. If it is faulty and reports say 80F to the ECU when the coolant is actually -25F the glow plugs glow time will be greatly reduced making for hard starting.

And what happens if you unplug the sensor and try to start it?

k_pt said:

Cam sensor can cut if off in some engines. Shut off solenoid on the IP too.

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On an ALH?

jokila said:

On an ALH?

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On some PDs yes, on VEs doubt they do

my pd will start with the cam sensor connected but not bolted to the engine, but wont run with no sensor plugged in.

k_pt said:

On some PDs yes, on VEs doubt they do

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VE engines don"t have a cam sensor they only have the needle lift sensor in one of the injectors so that the ecu can determine the start of the injection. PD engines can work with a broken cam sensor but they will usually crank longer.

1.4TDI PD said:

VE engines don"t have a cam sensor they only have the needle lift sensor in one of the injectors so that the ecu can determine the start of the injection. PD engines can work with a broken cam sensor but they will usually crank longer.

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I've seen broken cam sensors shutting down the engine, even in 1.4 tdis

I had an example at my shop days ago, 1.4 TDI AMF.

k_pt said:

I had an example at my shop days ago, 1.4 TDI AMF.

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In theory the engine should work without a working cam sensor. I had one example with audi a3 1.9tdi ATD with broken cam sensor and the engine was working normally but if the sensor sends out wrong signal it might fool the ecu into thinking that the camshaft is in the wrong position and it might not start.

I was having similar thoughts about my 2002 Wagon last weekend when I took it on a 2,500 mile round trip to Wisconsin. Temps in the teens and lower, snowing a lot of the time. A breakdown wouldn't have been fun, and with 380K on the car I felt like I was tempting fate. However, I know these cars pretty well, having owned several MKIV ALHs since '02 and selling parts for them, and the truth is they're about as dead reliable as any vehicle out there. They simply don't seem to suffer random failures or breakdowns, as long as they're properly maintained.

Carry a relay 109 (everyone should), and some replacement fluids. Perhaps a fuel filter in case you get a really bad tank of fuel. Beyond that, the odds of correctly predicting what will fail are low. Trust the car.

No cam sensor in an ALH TDI engine.

A failed MAP (aka boost pressure) sensor can cause a dead TDI, IIRC.


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Thanks for the responses.
I think I will replace the crank position sensor since it has unknown
milage on it with a OEM one. The Topran one only lasted about 1 1/2 years.
And either clean or replace the map sensor. Good reminder on the 109 relay
and a fuel filter on a trip.I agree that these cars can be dependable if you stay
on top of the maintenace and use good parts.
Cheers

I have almost 400K on my original crank sensor. Its just an inductive pickup sensor, really simple. Its not like the hall effect sensors which have a much higher failure rate.

I have replaced VERY few CKP sensors on ALHs. I have replaced quite a few more on BEWs and BHWs, which seem to be much more sensitive to a poor signal.

That said, I still wouldn't carry a spare in any of my cars. I think you can worry yourself to pieces if you get too crazy with these sorts of things. Proper PM, and not neglecting the car, will almost always go a long way to making it a reasonably reliable car. But in the end, there is always something that could happen that you didn't think of.

Aside from some very remote regions, a cell phone is generally the only thing you'll really want working because that means everything else can be obtained in some fashion, even if a tow truck is involved.

I do tend to proactively replace certain items if I am in an area doing something else anyway. I've had a few mishaps over the years, but never left completely stranded, and that says a lot because I drive a lot, and 90% of my driving since I have been driving have been in a Volkswagen.