TDI ECU INPUT-OUTPUT

S

SkyPup

Guest
Someone mentioned that stepping on the accelerator pedal (didn't want to call it a "gas" pedal) and the brake pedal at the same time resulted in some unwanted actions on behalf of the TDI engine. Here is some information on the new version of the TDI ECU from the Robert Bentley manual that should shed some light on what is going on when you step on the clutch, accelerator, or brake pedals all at the same time.

The accelerator pedal is directly connected to the Engine Control Module (ECM) via a potentiometer. This eliminates the need for an accelerator cable and is known as "drive by wire." The ECM also controls all glow plug functions and cruise control.
Basic fuel metering is determined by engine speed and engine load. When the key is switched on and the engine is started, the fuel cut-off valve opens and fuel flows into the injection pump. The ECM receives engine speed information from the Throttle Position Sensor (TPS). These signals are modified by the Engine Coolant Temperature (ECT) sensor, the Mass Air Flow (MAF) sensor, and the fuel temperature sensor. The ECM then signals the quantity adjuster which allows the proper quantity of fuel to be metered sequentially to the mechanical injectors. The ECM also uses the same information to determine the correct moment of injection which is the ignition firing point. The ECM monitors the operation of the quantity adjuster via a signal received from the modulating piston displacement sensor and makes corrections to the fuel quantity as required.
The ECM monitors the operation of the cold start valve via a signal received from the needle lift sensor attached to fuel injector #3 and again makes corrections as required.
Turbocharger boost pressure is regulated by the ECM based on a signal from the Intake Air Sensor (TAT), a vacuum connection to the intake manifold, and ambient pressure from an internal Barometric Pressure Sensor (BARO) . The wastegate bypass regulator valve receives output from the ECM and controls the vacuum signal sent to the turbocharger wastegate.
In order to prevent possible damage from simultaneous application of the brake, clutch, and accelerator pedals, the brake pedal switch, brake light switch, and clutch pedal switch, all signal their respective positions to the ECM. These signals are also used by the ECM during cruise control operation.

To put this all in better English:

The ECM basically takes digital input signals from the following components:

#3 fuel injector needle lift sensor Engine Speed Sensor (RPM)
Mass Air Flow Sensor (MAF) Engine Coolant Temperature (ECT) Clutch Switch
Brake Light Switch Brake Pedal Switch Throttle Position Sensor (TP)
Modulating Piston Displacement Sensor
Fuel Temperature Sensor
Cruise Control Switch
Vehicle Speed Sensor
A/C System
CAN BUS data link connector

After processing these input signals in various relations to each
other, the ECU provides these digital output control signals:

Malfunction Light Indicator
Glow Plug Light Indicator
EGR Vacuum Regulator Solenoid Valve
Glow Plug Relay and 4 Glow Plugs
Coolant Glowplug Relay and 3 Coolant Glow Plugs
Turbocharger Wastegate Bypass Regulator Valve
Fuel Injection Quantity Adjuster
Fuel Cut Of f Valve
Cold Start Injector
Instrument Panel
CAN BUS data link connector

Hope this helps, rememebr that the CAN BUS data link connector in the new TDI's is a digital bus setup, much different than the older analog version. Data rips much faster in digital form and can go two ways at the same time along one wire.

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99 JETTA TDI HERR WETTERAUER TORQUEMEISTER
98 KAFER WETT SPEKTAKULARE TURBOKOMPRESSOR
97 KTM 620 ADVENTURE RALLY PARIS-DAKAR SUPER THUMPER
 

Craig

Veteran Member
Joined
Apr 8, 1999
Location
Kitchener, Ont., Canada
Wow! Great info! Sounds like an F16 instead of a lowly diesel car. My guess it is not much different from any modern gas car as far as ECU control.

I assume that the new Pumpe-Duse is even worse. Possibly the injector pumps are all balanced by the ECU.

A far cry from my old 85 TD. The only thing electrical was one solonoid (for the pump I think). I heard you could run a wire from a battery, push start the car, and run without any electrical system. The amateur mechanic who now has it loves these older diesels. All mechanical--he can fix them!
 
S

SkyPup

Guest
That reminds me of a question I had been meaning to ask of all you out there. Has anyone push started their TDI? I mean with a compression ratio of 19:1 and a compression pressure of about 500 psi (take off the injector and screw in a compression checker and it should be around 500 psi in a good TDI), it seems it would be more likely that you would end up busting a gear or bending a motor mount than starting the engine.
Is push starting a TDI with a dead battery a good proposition or just an easy way to wreck more havoc?
 
M

mickey

Guest
If you put the car in 5th gear, I can't imagine you'd hurt the thing by push starting it. In a lower gear, you'd probably not accomplish anything but I still don't thing you could hurt the car. The tires would "lock up" and skid before you would break anything.

Craig, you said the Pumpe Duse might be "even worse". I disagree with the word "worse"! These new OBD II cars make sense to me. I've always done my own repairs and maintainance, even to the point of rebuilding engines. But I never could wrap my brain around "mixture" and "dwell angle" and all that other voodoo the old-timers are so nostalgic for. I understood the theory, but in practice I always had to take the car to a good dyno shop to have it tuned properly. Now, any computer nerd can be a mechanic. It's the old timers who don't understand these "newfangled computers" who are out of their element. The tables have turned! I was at a Ford dealer with my dad recently, watching the diesel tech (my cousin) diagnose a whole basketful of problems with his '99 Powerstroke. Lights were going on all over in my brain, while my dad's eyes slowly glazed over. It was pretty funny.

-mickey
 

Andrei Rinea

Veteran Member
Joined
Jan 21, 2002
Location
Europe, Romania, Bucharest
TDI
VW Tiguan 4Motion 2.0 TDI 170HP (engine CBBB)
SkyPup said:
That reminds me of a question I had been meaning to ask of all you out there. Has anyone push started their TDI? I mean with a compression ratio of 19:1 and a compression pressure of about 500 psi (take off the injector and screw in a compression checker and it should be around 500 psi in a good TDI), it seems it would be more likely that you would end up busting a gear or bending a motor mount than starting the engine.
Is push starting a TDI with a dead battery a good proposition or just an easy way to wreck more havoc?
First of all excuse me for replying after only 8 years ( :D ).

Yes, I've push-started my TDI (1Z engine) many times and it didn't ruin any engine mount, timing belt or anything else. It started excellent. Anywayz a battery replacement still is the way to go.
 

42hawkeye

Member
Joined
Feb 16, 2007
Location
NW Iowa
TDI
03 Beetle
Mass air flow sensor

Okay, experts...

This is all very interesting, but what are the "unwanted actions". What happens?

The main reason I ask is that I have an 02 beetle w/automatic and seem to remember holding down the brake and giving it a little pressure on the pedal (I have no explination or reason for doing this, I just did it?) I didn't stomp on it or anything, but just gave it a slight rev. When did I do this? I don't know. I can't remember... maybe a week or two ago?

Last week (in warm weather) my blue temp light stayed on and then it turned to flashing blue. The dealer thought that it may have been the the coolant level was low. The light went off the next day.

Yesterday, I was driving down the interstate at 70mph and I lost the top end. It sputtered down to 60mph. After a little bit of "testing" during acceleration it continued to sputter. It somewhat "fixed" itself, but I could tell that the exceleration leveled off at about 2800rpm. It would continue to accelerate, but not near what it should have been.

I took it to the dealer today and they said the mass air flow sensor was bad.

Does anyone think that this was related to my little tap on the accelerator when the brake was on?

???
 
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42hawkeye

Member
Joined
Feb 16, 2007
Location
NW Iowa
TDI
03 Beetle
Always check with the TDI club first.

uh, oh. I forgot to mention that yesterday I was driving in the pooring rain for about 4 hours.

Other discussions on this forum have led me to believe that water got in the electrical plugs. The kentucky memeber "paramedick" really got me thinking when he said "dollar to donuts it's water in the connectors" on another thread of the same topic.

Hmmm.. Now I guess I am going to have to decide whether to pay the price for not checking with club members first, or tell the dealer to put back the old MAF sensor?
 

FOG

Veteran Member
Joined
Nov 5, 2005
Location
Hatfield, PA
TDI
'02 Golf GL 2-Door
Mickey, Our TDIs do not have OBDII. All OBDII cars have OXs before and after there Cats. TDIs have 1 OXs before the Cat. only. Walt
 

BKmetz

Administrator, Member #10
Staff member
Joined
Sep 25, 1997
Location
Illinois
TDI
2015 Passat, titanium beige, 6MT
.

FOG said:
Mickey, Our TDIs do not have OBDII. All OBDII cars have OXs before and after there Cats. TDIs have 1 OXs before the Cat. only. Walt
Mickey quit TDIClub in 2002.

.
 

canadianveedub

Vendor , w/Business number
Joined
Jul 24, 2006
Location
Edmonton AB, Canada
TDI
2002 Golf
"The ECM receives engine speed information from the Throttle Position Sensor (TPS). "

The ECM receives engine speed information from the engine speed sensor. It recieves "requested torque" from the TPS.

"Turbocharger boost pressure is regulated by the ECM based on a signal from the Intake Air Sensor (TAT), a vacuum connection to the intake manifold, and ambient pressure from an internal Barometric Pressure Sensor (BARO) . The wastegate bypass regulator valve receives output from the ECM and controls the vacuum signal sent to the turbocharger wastegate."

Turbocharger boost pressure is regulated by the EMC based on info from the IAT and the MAP sensor which is built into the intercooler piping. The turbocharger control valve sends a vacuum signal to the variable nozzle actuator that controls the angle that exhaust gasses hit the turbine blades. there is no wastegate.
 

vwmikel

Vendor , w/Business number
Joined
May 5, 2005
Location
Las Vegas, NV
TDI
'94 Golf Sport TDI
FOG said:
Mickey, Our TDIs do not have OBDII. All OBDII cars have OXs before and after there Cats. TDIs have 1 OXs before the Cat. only. Walt
Um, OBD2 is a diagnostic standard mandated by government regulation as of 1996. Plain and simple, diesels don't have O2 sensors unless they are the new PD's which we finally got in 2004. All US market TDI's are fully OBD2 compliant.
 

eluwak

Veteran Member
Joined
Aug 1, 2001
Location
Eustis, FL
TDI
2006 Jetta 5sp Pkg 2 Black/Anthracite
BKmetz said:
.



Mickey quit TDIClub in 2002.

.
And everything but GD long before that... Man... The haydays of TDIClub... :D

LoL... I just noticed that SkyPup and Mickey are noobs :p
 
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KERMA

Vendor , w/Business number
Joined
Sep 23, 2001
Location
here
TDI
currently 99 beetle and 2011 335d
BKmetz said:
.



Mickey quit TDIClub in 2002.

.
And he sold the Evil Beetle... to me. ;) Can you say project car?:cool:
 

FOG

Veteran Member
Joined
Nov 5, 2005
Location
Hatfield, PA
TDI
'02 Golf GL 2-Door
See post #4 BKnetz from mickey (newbie)
vwmikel OBDII is for gas eng. cars, trucks and suv, 96 on. OBDII looks to see if the Cat. is working good. To do this they have 2 Oxs. 1 before the Cat and 1 after to check that the Cat. is working Good. TDIs have 1 Oxs (PDs) before the Cat. only, OBDI. Just the Plug is the same and sum cars had that plug in late 94 and up. Walt
 
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