P0638, P0221, P0507: TB, TPS, Something else?

[jonny-bird]

Hello all. My 2004 A4 1.8T Quattro recently exhibited some driving issues. The throttle began to have a mind of its own both at idle and when driving, it wouldn't go any faster than 40 mph, the idle would bounce between 800 and 1600 rpm, and the car would shake during idling. Three lights came on: check engine, traction control, and EPC.

I connected my scanner to it and retreived the following codes:

P0638: Throttle Actuator Control Range/Performance (Bank 1)

P0221: Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance

P0507: Idle Air Control Systems RPM Higher than Expected

I have been doing a lot of research on various VW and Audi forums and would just like to get some idea for the most likely cause of this problem without throwing parts at it that it doesn't need. From my reading, there are many people with similar symtoms--and hence, a whole slew of different fixes--but unfortunately they rarely post their DTCs, so I don't know if it's exactly the same problem as mine.

It seems to me that it is either the throttle body or the accelerator pedal sensor. (I believe that the last code--P0507--is only a result of the RPM swing at idle and not a separate issue.) I have removed both of them. The throttle body, while it had some oil buildup in it, wasn't overly dirty. I popped the cover off the electrical box and the contacts were very clean. The contacts of the accerlerator pedal were also clean.

So, what do you think: throttle body, accelerator pedal sensor, mass air flow sensor, fuel filter, vacuum lines?

Thanks.

[Steve@Unitronic]

This is a good example to show people also how our definitions are different than what the code scanners show.

for example on yours:

16605/P0221/000545 - Angle Sensor for Throttle (G188): Implausible Signal
Possible Symptoms

Malfunction Indicator Light (MIL) active

Possible Causes

Wiring/Connector(s) from/to Throttle Body Control (J338) faulty

Possible Solutions

Check Throttle Body Control (J338)
See Measuring Value Blocks (MVB) 060+
Check Wiring/Connector(s) from/to Throttle Body Control (J338)

Special Notes

When found in the NAR 2.0l TFSI: (BPY, CCTA and CBFA) check TSB 01-09-04 or 2018652 for a wiring repair at the Throttle Body.

***********************************************

16891/P0507/001287 - Idle Control System RPM: Higher than Expected.
Possible Symptoms

Malfunction Indicator Lamp (MIL) active

Possible Causes

Throttle Valve Control Module (J338) dirty/faulty
Wiring/Connector(s) from/to Throttle Valve Control Module (J338)
Vacuum Leak

Possible Solutions

Check Throttle Valve Control Module (J338)
Check Wiring/Connector(s) from/to Throttle Valve Control Module (J338)
Check Intake System for Leaks

Special Notes

When found in the NAR 2.0T (BPY) check RVUTB: 01-09-03 or 2018919 for updated Crankcase Breather Valve
If the breather valve is faulty, full engine vacuum is typically found when removing the oil cap at idle.

***********************************************

The code scanner is good tool to attain the codes but i would stop there then go here for our definitions: Wiki.Ross-Tech (http://wiki.ross-tech.com/wiki/index.php/Main_Page)


So from what i see everything is pointing towards the TB and possibly the wiring going to it, it is very possible you also have a leak somewhere.

I would start with performing a TB Alignment, but you need a Ross-tech:VAGCOM cable to do this.

A Throttle Body Alignment is performed by opening VAGCOM with the key ON and the vehicle NOT running!

Select the ENGINE controller->Measuring Blocks-> Group 060->switch to Basic Settings

it will then count off, till it says ADP OK, then wait 30sec and its done!

[jonny-bird]

I changed the TB, and in doing so, I found a bunch of vacuum lines that were split, check valves that were corroded, and the plastic PCV tubing was cracked and practically gone. I replaced all of it and added an AFE cold air intake at the same time. Now, I have no more codes and the engine runs great except the idle is a little high (about 1200 when warmed up). Could this be a vacuum leak somewhere, a sensor, or something else entirely?

[Grip99]

I changed the TB, and in doing so, I found a bunch of vacuum lines that were split, check valves that were corroded, and the plastic PCV tubing was cracked and practically gone. I replaced all of it and added an AFE cold air intake at the same time. Now, I have no more codes and the engine runs great except the idle is a little high (about 1200 when warmed up). Could this be a vacuum leak somewhere, a sensor, or something else entirely?

Did you do an TB Adaptation?