No TCM on 2001 Jetta with 01M

Hello all and thanks in advance for your feedback or assistance on this.

I have searched the forums here and on the net at large for information on this particular issue. Some close, but just not quite...

So, I have a 2001 Jetta with 01M transmission, engine and transmission from a similar year Beetle (was told this by the seller when I bought the car, anyway to look up engine/transmission numbers?). When I connect my Foxwell code reader with VAG module. I can see my ECM, air bags, instruments, ABS... as far as I can tell, everything that the car should have -except- the TCM.

When I was attempting to diagnose things earlier this year, I found that I had a bad battery (I could read the TCM with a battery charger on the car, could not read it without).

I have since replaced the battery and still cannot read the TCM.

I am hoping to go through the connections and grounds near the ECM and TCM under the cowl. I hope that this will let me know if I have a faulty TCM or something else going on.

Would I appear to be going in the right direction here?

If it looks like I need to replace the TCM, what are my best options once I have a part number directly from the unit in the car?

Thanks again in advance.

I am confused, as once again (happens a lot here), information has been left out.

What is the actual issue here? Does the transmission fail to function properly?

alongjordan said:

When I connect my Foxwell code reader with VAG module.

Click to expand...

Have you contacted Foxwell about this?
Maybe there's a program update on their web site?

Sorry... that would probably be helpful...

The vehicle is presently non-running.

The last time it ran, it made a drive from Houston to Texarkana. Gripe economy seemed to be about 45 MPG. After a fuel stop, it suddenly had a hard time starting and went into limp mode.

I pulled a code from the TCM at that time that had to do with the speed sensor since then, I have been having issue reading that the TCM exists. Thought it was related to a bad battery (recently replaced that).

OK, well get it running first. The TCM can be dead and the car will still start and run (and move, albeit with only 3rd and reverse and full line pressure).

alongjordan said:

I pulled a code from the TCM at that time that had to do with the speed sensor since then, I have been having issue reading that the TCM exists. Thought it was related to a bad battery (recently replaced that).

Click to expand...

Do you remember the code?
Maybe it was the engine speed sensor?

Earlier this morning, I connected to the car with the Foxwell diagnostic reader (second time since I did updates on it yesterday) and magically, I was able to ready codes from the TCM. They are as follows:

00777 - Accelerator Position Sensor (G79) - sporadic - Implausible signal

00660 - Kickdown Switch Throttle Position Sensor - sporadic - Implausible signal

00529 - Engine Speed Signal Missing - Intermittent

00545 Engine-Transmission Electrical Connection - Sporadic Open/short circuit to earth

01314 Engine Control Module - sporadic - No Communication

TCM Info:
VAG Number - 01M927733KA
Component - AG4Getriebe01M 4836
Soft. Coding - 00000
WSC - 00000

While also connected to the ECU, I can read the Throttle Position Sensor from Live Data feed and it appears to be responsive to moving it through its motion and 0% to 100% seem to be feeding to the ECU properly.

Attempted to start the engine also, no love at this moment. Busy time for me right now, so I'm 'sneaking' a poke at this vehicle here and there.

Thanks for all the help.

Whenever I see multiple electrical codes I think: grounds and/or corroded connections.

flee said:

Whenever I see multiple electrical codes I think: grounds and/or corroded connections.

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2X on the above.

If the body ground connection under the battery tray is bad then anything that grounds to the body is bad.

Check fuses 29, 32, 34, and 43 in the inside fuse box.

Also check fuse 176 (110 amps) above the battery.

Do all the dash board lights go on when you turn the ignition on s/a the glow plug light?
This should rule out relay 109.

wonneber said:

2X on the above.
If the body ground connection under the battery tray is bad then anything that grounds to the body is bad.
Check fuses 29, 32, 34, and 43 in the inside fuse box.
Also check fuse 176 (110 amps) above the battery.
Do all the dash board lights go on when you turn the ignition on s/a the glow plug light?
This should rule out relay 109.

Click to expand...

I will be returning to this next week, glad to have access to the collective experience here.

I will go back over those fuses and be chasing grounds (engine compartment and in the cowl for sure, possibly/probably deeper in the car) .

Also, I have identified a couple of very suspect wire splices I. The engine harness that I’ll be addressing. I have found and ordered a complete engine bat wire harness from a seller on eBay that should be in by Thursday next week.

Definitely going to take another look at the fuse box on the battery. I seem to recall some corrosion on the dog bone shaped metal bits that look like they are bridging between a common bus (fed by the positive battery cable) and several other leads going into the rest of the wiring on the car

I have managed, with the help of a local mechanic friend, to get the vehicle running. Short version on the engine running is that I had air in fuel lines and changing to a correct fuel filter, replacing some fuel lines, priming the IP with a handheld vacuum pump, and clearing any remaining air via bleeding the injectors and the car/engine runs again.
I can drive the vehicle at low speed. Honestly can't tell if it's shifting or not.
What I can tell you is that I can about 80% of the time read the TCM with my Foxwell scan tool (recently updated via Foxwell) with the car in KeyON EngineOFF. I cannot read the TCM at all while the engine is running. It posted the same codes as before.

00777 - Accelerator Position Sensor (G79) - sporadic - Implausible signal
00660 - Kickdown Switch Throttle Position Sensor - sporadic - Implausible signal
00529 - Engine Speed Signal Missing - Intermittent
00545 Engine-Transmission Electrical Connection - Sporadic Open/short circuit to earth
01314 Engine Control Module - sporadic - No Communication
TCM Info:
VAG Number - 01M927733KA
Component - AG4Getriebe01M 4836
Soft. Coding - 00000
WSC - 00000

Click to expand...

It took me a while to get back to working on the car...
Responses to suggestions from you all below:

Originally Posted by flee View Post
Whenever I see multiple electrical codes I think: grounds and/or corroded connections.

Click to expand...

2X on the above.
If the body ground connection under the battery tray is bad then anything that grounds to the body is bad.
Check fuses 29, 32, 34, and 43 in the inside fuse box.
Also check fuse 176 (110 amps) above the battery.
Do all the dash board lights go on when you turn the ignition on s/a the glow plug light?
This should rule out relay 109.

Click to expand...

I have crawled and cleaned all of the engine compartment and plenum grounds. I have verified that there is good ground (0.000 ohms resistance) between the grounding pin in the TCM harness connector and ground at the plenum as well as the negative cable on the battery.
I have checked and verified the fuses suggested, both visually and measuring for voltage across them.
I have replaced Relay 109 in what I will describe as a cross between almost desperation and as a result of the glow plug light not coming on one morning when I went to start the car. There was a code in the ECU for the Glow Plug light not being lit on the Instrument Panel.
So, I guess I'm at asking questions again...
Is there a way to test a TCM? Would a VW dealer service department be able to do this? Cheaper to just buy a "tested good" used one?
Is it possible that the ECU is faulty?
What is next?
Again thanks in advance

It's very possible modules can go bad, especially if water gets in them. I'd imagine the tcm is well sealed since it's in the cowl panel, but if the seal in the connector failed, that's a done deal. Either it will connect to software or it won't. If you had VCDS you could refresh the CAN gateway to see if it'll detect the TCM. If it doesn't I'd say it's bad. If you don't want to get or don't have someone close by who has VCDS you can always replace the TCM.

Nero Morg said:

It's very possible modules can go bad, especially if water gets in them. I'd imagine the tcm is well sealed since it's in the cowl panel, but if the seal in the connector failed, that's a done deal. Either it will connect to software or it won't. If you had VCDS you could refresh the CAN gateway to see if it'll detect the TCM. If it doesn't I'd say it's bad. If you don't want to get or don't have someone close by who has VCDS you can always replace the TCM.

Click to expand...

So is that a either will connect or won’t connect with VCDS?

Pretty much yeah. Unless you have some butchered atrocity with your wiring harness, modules either work or they don't. Rarely are they intermittent.

Have you checked the ground behind the left side of the dash?
The trans circuits uses fuses 7, 11, 13, 15, and 31.
Check these for good connection also.

There should be someone in Houston with VCDS.
There's a list of people with it willing to help with it.
It should be in one of the top forums.