Hi all,

My car, Mk 2 with a GT engine, was suffering from jerky acceleration on low throttle, I attached an engine diagnostic tool and it showed fault code 00518, which is a faulty Throttle Position sensor.

I purchased the Corrado VR6 hella replacement as suggested on another thread on here, fitted it about a month ago and all problems and codes seemed to disappear.

Until today that is when the exact same problem and fault code returned.

Is it a faulty new sensor or is there anything else that could be causing this?

I'm guessing it could be a faulty ECU?

 

Thanks for any help

Andy

Take the TPS off and test it with a multimeter first. Also check the wiring to the TPS. 

I've heard of new sensors being faulty but if that's the case they are usually faulty right out of the box. Failing after just a month would make me suspect something else.

Thanks for your response (again!), any idea what readings i'm looking to get.

I know I saw them at some point in a thread but can't for the life of me find it again.

Thanks

Andy

 

Thanks that's great

So, I've been out with my multimeter today and found the following:

As I played around with the cables going into the multiplug the brown, earth, pulled free.

I thought brilliant, it must've been a tempermental earth all along!

I pulled the plug to pieces and soldered the earth back onto the terminal.

After this I got these readings on my multimeter

Voltage across 1 & 2 throttle closed .383. Should be 0.5-1.5

Voltage across 1 & 2 throttle open 4.13. Should be 3-5 so ok

Resistance across 1 & 2 throttle closed 1.075. Should be approx 1.5

Resistance across 2 & 3 throttle closed 2.908. Should be approx 2.5

Resistance across 2 & 3 throttle open 1.175. Should be approx 1 so ok.

Earth connection 01.1. Should be 0. Not sure why it read 01.1 rather than 1.1?

 

I then cleared any codes from the ECU and went for a drive only to find the fault code 00518 to have reappeared.

Do the readings in bold seem to suggest the sensor is knackered or is the earth connection likely to be the fault?

 

 

Just for fun I tested the dreaded blue temperature sender as well,

It read a resistance of 1.364 when cold and 0.258 when warm.

Does anyone have accepted readings for the blue temp?

 

Thanks

Andy

 

Edited 12 April, 20179 yr by fathands

Usually earth connections have a very low resistance, maybe try cleaning up the earth connections and retest?

 

As for the blue temp sender readings I did find this from an old Club G40 post. They all use the same temp sender so will apply to the GT too.

 

Simply measure resistance across the two poles
3.2k ohms - 4.2k ohms at 10 degrees
2.1k ohms - 2.9k ohms at 20 degrees
1k ohms - 1.4k ohms at 40 degrees
520 ohms - 670 ohms at 60 degrees
280 ohms - 370 ohms at 80 degrees

 

You don't say what temperature yours was at but assuming cold it was in the region of 10 degrees then yours does seem a bit low.

I haven't got any sort of reference on my temperature gauge so it was just a guess.

I'll try it again when its completely cold.

 

Do you know where the throttle position sensor earths to, it dissapears into the loom and can't seem to locate it in the haynes manual either.

Also do you think that because the throttle closed voltage is very low, thats what is causing the hesitation on low throttle?

I'm at work at the minute but will clean the main earth contacts when I get chance and re-test.

 

Thanks again

Andy

I think it just goes into the loom and earths via one of the two (I think) earth connections on the main earth terminal on the battery. 

So back to it today,

I have replaced terminal 1with a cable straight to the battery negative to ensure a good earth with no resistance.

I then retested all the measurements, first column is the previous reading, second are the new reading. The third column is a reading from my (what I presume is) genuine GT but faulty sensor that I replaced

 

Voltage across 1 & 2 throttle closed                     .383        0.37         0

Voltage across 1 & 2 throttle open                        4.13.       4.17        4.5

Resistance across 1 & 2 throttle closed               1.075.      1.074     0.85

Resistance across 2 & 3 throttle closed               2.908.      2.90        5.7

Resistance across 2 & 3 throttle open                  1.175.      1.17       1.18

Earth connection                                                    01.1         0             0

 

So to me it looks like the old sensor was definitely faulty and the new sensor is partially down on voltage when closed and resistance across 1 and 2.

 

There is still a constant fault code on the ECU of 00518 so I'm guessing this slight variation in reading is enough to upset the running.

 

Anybody have any other thoughts?

Is it worth me swapping the ECU or shall I just return the sensor and get a replacement?

 

Thanks

Andy

 

 

TPS test values Polo GT | Club GTI

Had to find a solution to a worn out TPS recently, it was hard. See this thread on CGTI if you have to attempt it yourself, i've done all the hard yards already.

wow

Yeah, your choices are £1000 for a new TB and sensor from VW, or the late VR6 sensor with the wrong drive (HELLA 6PX 008 476-101) and make up the conversion to fit it. All the CW rotating ones make the car feel very flat everywhere apart from WOT because you only get 2.2v at 2nd butterfly and the GT sensor gives 3.7 at this point.

One other issue that i've learned is indicative of a faulty TPS is the over-run working intermittently. Its a big red flag.