99 Passat TPS vs ECU Memory

I have a 99 passat, 1.8L 4cyl turbo. She was dead for too long and upon charging the battery and starting her she idles rough, around 600-900, levels out around 1000 after a couple minutes, but then when you give her gas she’ll maybe reach 2000rpm before dropping and almost stalling even if pedal is still pressed. Code is P1545 for throttle position controller malfunction. Was thinking ECU lost memory from being dead too long and needs to be reprogrammed but radio presets didn’t reset… Tried testing TPS with multimeter but need some guidance as it’s 8 pins vs the regular 3. Inside of throttle body is clean, didn’t adjust, just pulled hose and peeked inside to rule out excessive carbon build up. Other codes that generated while messing with her were P1544 for throttle actuator sensor, signal high and P0123 for throttle position sensor circuit, high input. Would hate to replace throttle body/TPS if the ECU just needs reprogramming. Any input on how to diagnose better/test 8 pin TPS would be greatly appreciated! Thank you thank you!



So definitely ECU issue requiring reprogramming?

Drive the vehicle and see if it will re-learn the operating parameters.


Would jacking the car off the ground and ‘driving’ in the driveway work? Tried taking it around the subdivision and it jerks and stalls quite a bit, therefore loses power steering, and is a bit dangerous. Do you know how long it approximately takes to relearn? Thank you for your help!

My 1999 Dodge Durango does the same thing when I disconnect the battery to do some work on the car. Sputters and idles rough, I don’t even try to drive it. In my case I just let it idle for about 10 minutes, playing with the rpm from time to time.
Lately I use a “memory saver” when I have to disconnect the battery. Works like a charm.

Jacking the vehicle up so the drive wheels are off the ground is like a chassis dyno.

It allows the operation of the engine/transmission without driving the vehicle.

The difference is, it doesn’t apply a load to the engine/transmission.

Try it!


I’ve tried letting it idle and playing with the rpm but that doesn’t work. Definitely using a memory saver from now on, thanks!!!

A memory saver doesn’t work when a battery goes dead.


I was thinking that too, that the lack of load may prevent it from working. But you’re right, worth trying! Maybe I’ll see if anyone wants to learn stick under the worst conditions possible while she’s jacked up :joy: I was just pondering, if the ECU isn’t programmed correctly, wouldn’t the TPS throw erratic voltage and look like it’s malfunctioning anyway? Thanks again!

I wouldn’t recommend it

you’ll just confuse your ABS module

And why do I say that . . . ?!

Because the module will see “speed” on the front, but 0mph on the rear

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Since you have a P1545 code I would check the wiring to the sensor to verify it is okay. If that is good then you may need to replace the sensor.

Thanks! Would the ABS module eventually relearn after I’m able to return to driving on the road?

If the ECU isn’t synced to the TPS, wouldn’t there be faulty codes though? I tried testing the wires with a multimeter but it’s a 8 (only 7) pin TPS. Do you know how to test an 8 vs a 3 pin? Thank you thank you!

In order to test the wiring you will need the wiring diagram to show you where the wires tie to and test them to make sure they are connecting to the points they are supposed to tie to.

If the ECU lost its memory and is sending faulty signals though, wouldn’t the test not accurately tell me if the TPS is indeed the issue? Thank you!