16497 - PLEASE help !

[mikes3]

2003 S3 - BAM engine

16497 - Intake Air Temp G42 - signal too high

Ok, so this has been running a couple of weeks now. The ECU threw the code up and as a result, the car has lost power, intermittent boost problems and runs lumpy on idle.

I have sourced a brand new sensor from Audi, and replaced. Cleared the code, turned the ignition and the fault came straight back. I believe this fault has to show on 3 separate startups to show an Engine light on the dash (which it does).

Anyway, I scoured the net and found a couple of walkthroughs/guides as to the symptoms, causes and possible cures of the said fault. Both of them suggested that there should be 5 volts DC across the 2 connector plug terminals with the ignition on. I tested, and found nothing, zero volts. I gather that if the ECU sees the high or low voltage limit it will throw the fault. So, convinced I had a wiring fault somewhere, I set about finding it.

Stripped back the loom running under the battery tray and air box, traced the cable back as far as the loop near the pollen filter. I wanted to chase it back to the ECU, but the passenger wiper blade is jammed on the spline and Im having trouble removing it. I cut the cable at the loop, and tested voltage from te ECU - still nothing. (the cable back to the sensor is clear, and has good continuity).

I'm at the stage now where Im banging my head against the wall. Am I actually chasing a lost cause towards the ECU, or is some other sensor/signal somewhere causing the fault (ie MAF or MAP). I have removed the MAF and cleaned as per the guides on here, being very careful with it. No other faults showing on the diagnostic at all, only 16497.

To add to it all, I registered on ERWIN for an hour an pulled up the wiring diagrams, only to find the actual pictures weren't showing (using IE8). Does anyone know if the sensor cable routes directly to the ECU, or does it go via any connectors ? Maybe one has unseated or has a bad pin. I don't know.

I've chucked a lot of time and money at it so far, and I haven't got a pot left to pee in. Can't afford to be throwing new sensors at it without valid reason.

Any help from you guys is greatly appreciated. You will make a jaded (and very tired) Audi lover very happy.

Best Regards.

 

[NHN]

Should of come on here mate & asked before using erwin as thats a rip of I can assure you.

The G42 has as you say 2 legs, 1 goes to earth & is shared connection with other I suspect senders as it shows it as 220 Sender Earth, other leg goes to the J220 Motronic Control Unit pin 85, I would goto that pin connection disconnect the existing pin then add a new wire & test for any voltage from that new wire mate.

Also get a meter & test between the sender wire pin 1 & the pin 85 wire & see if there is continuity on that wire as it shows as straight threw between the 2 points.

Hope that helps.

 

[mikes3]

Yes you are right, it does seem a rip off, especially as it doesn't even work when you follow all of the OS instructions. Anyway, I guess I can ask the question now.

Does anyone have a wiring diagram I can look at please? I believe its the Motronic Control Unit - Its diagram 4/5, and shows the throttle control and intake air temp. I'd be extremely grateful.

Thanks very much in advance.

 

[mikes3]

UPDATE

Ok, I have managed to get to the ECU. Removed the plug and checked continuity to the pins of both wires. Good continuity on both, and clean between the two.

The bit I'm confused about is the pin numbers. Green goes to pin 81, Yellow to pin 91. No continuity between any other pins on each wire.

I really need the schematic wiring diagram now. Can't go any further without a definate location for the wires in the plug.

 

[NHN]

Huh, the schematic shows pin 85 which is pin 1 of the G42 sender as a blue/green wire & the pin 2 of the sender which is a shared sender earth for all senders it seems is brown/blue mate for an 03 BAM engine code.

 

[mikes3]

NHN - Well spotted.

I found a schematic, and saw the same problem. Turns out I posted the wrong pins anyway, but I still had the wrong numbers when I looked again. I had pins 82 and 101. These are the two wires for one of the knock sensors - the specific one is mounted at the front of the engine, under the mass of wires and coolant pipes. Also noticed the colours on the diagram didn't match up.
So, you guessed it, I had the two connectors in the wrong positions, IAT connector in the knock sensor, and vice versa. Swapped them around and cleared the faults, and BAM (literally) it worked. Went out for a drive, and its also boosting perfectly and all my horses are back ! I had the engine removed for a rebuild and had the car back off the garage like this. I should be annoyed with them, but strangely Im not. I've learned more in the past few weeks than I would've ever learned about my car. I have a brand new IAT sensor for sale now, and a new TIP fitted, not to mention silicone vac/boost lines and all my earthing points etc. rewired and clean. Looking forward to my holiday now - driving across to Hungary on Friday and now I really can't wait. Autobahns here I come.

Thanks for all who helped me with this. (in other threads too)
I really appreciate it.

The moral of the story is, don't trust a mechanic to be any good with electrical stuff ))))

 

[NHN]

Cool, knew it had to be the wrong wires somewhere.