2000 Jetta 1.9 TDI is reading 2 codes for electrical connecton

P0740 is the torque converter malfunction code. The converter is in between the engine and transmission. The fluid that you are seeing is transmission fluid. It needs to go to a mechanic to narrow it down from there.

http://www.partsgeek.com/mmparts/crank_position_sensor/volkswagen/jetta.html

Possible causes
- Faulty Torque Converter Clutch Pulse Width Modulation (TCC PWM) Solenoid
- Torque Converter Clutch Pulse Width Modulation (TCC PWM) Solenoid harness is open or shorted
- Torque Converter Clutch Pulse Width Modulation (TCC PWM) Solenoid circuit poor electrical connection

all 1.9 tdi engines with 8v cylinder heads have glow plugs out side cylinder head, you will find them easy. Torque is from 12 - 14 Nm.

P0740 Honda - Transmission Lock-Up Control System Fault Possible causes
- Low transmission fluid level
- Dirty transmission fluid
- Faulty torque converter clutch solenoid valve
- Torque converter clutch solenoid valve harness is open or shorted
- Torque converter clutch solenoid valve circuit poor electrical connection

Tech notes
On some Honda vehicles the P0740 code may be set by an overheating torque converter problem which is caused by an insufficient flow to the torque converter release circuit.

P0740 Honda Description
The torque converter clutch solenoid valve is activated, with the gear in D4, by the Transmission Control Module (TCM) in response to signals sent from the vehicle speed and the Engine Control Module (ECM). Lock-up piston operation will then be controlled. When the torque converter clutch solenoid valve is activated, the torque converter lockup clutch will engage creating a 1 to 1 RPM ratio between the transmission input shaft and the rotational speed of the torque converter.
Lock-up operation, however, is prohibited when A/T fluid temperature is too low.
When the accelerator pedal is depressed (less than 2/8) in lock-up condition, the engine speed should not change abruptly. If there is a big jump in engine speed, there is no lock-up.

Have the fault codes read and replace faulty units.

PO740 -- trans torque converter clutch

PO420 - converter as you said.

Do you have 2 or a bad O2 Monitor Sensor

If a converter goes bad in less than 12 years
or more ,you have to fix the reason it failed,
not just install a new one

The error code definition reads:

"Catalyst Efficiency Below Threshold Bank 1"





It's possible it might be the oxygen sensor, but it's more than likely the catalytic converter. This is a relatively common code for VW's.

You can google "p0420" and see the posts...

your vehicle is driving good, not slipping etc... because what i can see from what im reading you have an electrical problem with the transmission wiring.. check the plugs that plug in the transmission, and follow them, im sure you will find something skint up somewhere.

WHEN EVER YOU DISCONNECT BATTERY PCM LOSE MEMORY WHICH CAUSE POOR ENGINE PERFORMANCE.TAKE CAR TO VOLKSWAGON DEALERSHIP LET THEM REPROGRAM IT.