Faults P0101 & P0118

Morning!
2004 TDI PD BEW W/auto trans
CEL came on a few days ago, ran VAG and pulled these two engine TCs.
MAF implausible intermittent and coolant temp sensor signal too high intermittent
So I Checked for vacuum leaks with carb spray (no luck finding leaks) Replaced the air box filter, and threw in new coolant temp sensor, and cleared the fault codes
MAF code is gone, but I’m still getting the CTS fault.
The car seems to run fine, only noticeable thing I detect is a higher than normal RPM upon start up
Cam sounds ok ( at least I think?)
Any ideas suggestions on what’s going on

Anyone have a clue?

Dadwagon said:

Morning!
2004 TDI PD BEW W/auto trans
CEL came on a few days ago, ran VAG and pulled these two engine TCs.
MAF implausible intermittent and coolant temp sensor signal too high intermittent
So I Checked for vacuum leaks with carb spray (no luck finding leaks) Replaced the air box filter, and threw in new coolant temp sensor, and cleared the fault codes
MAF code is gone, but I’m still getting the CTS fault.
The car seems to run fine, only noticeable thing I detect is a higher than normal RPM upon start up
Cam sounds ok ( at least I think?)
Any ideas suggestions on what’s going on

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Have you had your coolant changed recently? I got this when I put generic green coolant in when it had the red g12 it is supposed to have. what happens if you mix it creates chunks because the chemicals don't mix. now if you do have green coolant in and want to keep it in you will have to fully flush your system with water to get all the gunk out if its not to late. that code for me was chunks going by the sensor.

There is the possibility that there are wiring problems. Since you have replaced the temp sensor, we will set that aside and assume that the problem is between the sensor and the ECU.

This isn't the usual time of year for this, but if there is rodent damage (they love VW wiring insulation for some reason) or any instance of rubbing, chafing, or other damage to the wires, you could have a disconnect that is causing this trouble.

It will take careful examination of the path from the sensor to the main wire bundle leading into the plenum for the ECU. Start with the plug itself - wires at the plug entry/exit can take a lot of stress.

Cheers and good luck,

PH

Your high RPM at startup coincides with the CTS DTC. The ECU is defaulting to a cold coolant value. I would check the wiring, the CTS is on a leg along with the VSS that runs back under the tandem pump area. Pull that whole leg up and out and look it over carefully.

Powder Hound said:

if there is rodent damage (they love VW wiring insulation for some reason)

Click to expand...

A now-retired coworker of mine had some rodent-chewed wires on his 2012 Camry a couple months ago. He had it fixed, but more appeared and he ended up trading for a new Camry).

In researching about this, he found out that for several years (including 2012) Toyota was buying wiring whose insulation was made from soybeans, which meant the wires smelled like food to the rodents.

Wonder if this explains your observation, PH?

The soybean wire covering story has been circulating for decades. For every manufacturer. I assume there is a kernel of truth somewhere, but the most likely main real reason is that rodents just like chewing stuff up. Squirrels are especially destructive. They've managed to chew soccerball sized holes in my house, and there is absolutely nothing edible for them.

Dannyboy said:

Every VW I had has some form of rodent damage whether it be wiring, hood insulation or hoses. If the car sits for a while that's usually when they go to town

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I drive mine every day and the little buggers are still trying to nest in my cabin air filter!

Alright thank you everyone for the replies, the car has been sitting so maybe I have some chewed wires, going to pull the bundle and follow oil hammers recommendation. Stay tuned

Okay so I pulled the wiring leg up, to the point where it goes into the big 2 inch loom and dives down under the car with a bunch of other wires

Everything I see looks okay, nothing chewed or frayed etc

Is there a way for me to test the connector ( volt meter) now that I have the connector out and accessible in front ?

So I did some testing with multimeter

CTS pins 1 and 3 show no voltage so I pulled the t14a connector - No voltage at t14a (pin 4)
Odd because I though those 2 hot CTS pins come from different legs? And the temp gauge works fine

I am getting good ground from both 2 and 4 Pins on CTS and 9 pin on t14a

Not sure what to check next?

So I have access to the ecu now, but don’t see how to determine individual pins within the unit and connector? How do I find t60/52 and t60/53?

Ok I tested per Danny boys advice and both 52 and 53 failed continuity test to CTS pins 3 and 4. And just to be clear, make sure I’m testing correctly, I’m testing female pins on both T 60 connector and CTS connector

Ok I had the t60 connector upside download retested and found good continuity at pin four of the CTS but no continuity at pin three of the CTS, What’s next? Do I have to replace that whole wire harness?

Ok, so I cut the wire on the CTS side to test continuity to the pin, all good there, so the issue is some where behind the CTS connector.

On the t60 side I think I’m having a problem finding pin 52 wire, I cut a brown blue, but it fails continuity to both pin 52 and the CTS wire. I highly doubt the wire is failed on both sides, more likely I cut the wrong wire.

I thought about trying to take the cover off the t60 connector to see exactly which wire feeds into Pin 52, but it’s way too brittle.

I see other brown blues, but don’t want to keep cutting blindly.

Any thoughts ?

I was able to pry off the cover on t60, upon close inspection, pin 52 is not wired at all. Instead is blanked with black plug/stem

CTs wire 3 is green/white, the closest color match I can find on t60 is pin 54 which is bluish or turquoise/ white, close, but not an exact color match

Any idea where else To look?

Any help here? There is no wiring schematic on the back cover of t60, and pin 52 is Blank/ plugged

Stop.

Before going further, you need to be sure you have the right model of VW engine / type.

You now have a little problem, in that you were clipping wires from the wiring harness, at the ECU end, and they were the wrong colors.

This signifies, that the either the wiring harness pin-out is different or that you have some unique assembly.

The Coolant Temperature Sensor (CTS) only has two active wires, and they have been described previously.

Essentially, the sensor , is a variable resistance, that changes, as the temperature goes up, with the ambient of (or zero value) being where the resistance would be -40C or similar, and where the high values (255 or $FF) would be +125C or similar.

What the ECU does is runs a known voltage through the resistance, and then channels that voltage to a voltage divider circuit, so that it can determine the "voltage" for the conversion to what is displayed on the cluster, then, into the ECU, as a dynamically changing variable, as the engine is running.

[see the diagram , later, still trying to figure how to add sketches/diagrams to the new BBS software]

But, since you have a break in the one wire, the Analogue-to-Digital converter, of the CTS sensor. is pegging at $FF or similar, then the ECU runs in default mode, until you get it fixed. [see second picture with variable resistance cut out of voltage divider circuit].


So, until you get the right wires, and the correct "Pin-out", the one pin should not be "plugged", as you describe.

What happens when you count backwards, from the other end?

Does this result in the "correct" color wire?

If so, then, you know you had the plug/socket upside down from the diagram.