16490 - Barometric Pressure Sensor (G71) / (F96)

txtruck987

Member
Joined
Aug 19, 2018
Location
Houston
TDI
2001 Jetta
Hello all, and preemptively thanks for the help, these forums have been a godsend over the years.
This code appeared about a month ago. It comes and goes and seems to come on and stay on when the engine is warm. It puts the car in limp mode and the only thing that resolves it is cycling the key on and off a few times until the MAP sensor starts to register again.

This is a photo of VCDS groups 010 & 011. The Boost actual and MAP are stuck at 969.0 mbar and will not move. The N75 also stays at 92.4%.
If I turn it on and off a few times, it goes back to normal.

Things I have tried.
Replaced map sensor
Replaced all vacuum lines
Replaced N75 with N18.
VNT Actuator moves freely
Wires to MAP sensor had some knicks in the wire jacket so cut and reattached to make clean connection.
Cleaned MAP connection, cleaned ECM connections
Cleaned all grounds (By ECM and under battery tray)
Rosstech info on fault shows one of the possibilities for the code as ECM going bad, and that is where I am at, but wanted to see if anyone had any insight as far as what this could be and if I missed something little.

2001 Jetta TDI
Car is almost stock, with EGR delete, malone 1.5, and 520's.

Thank You.
 
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eddieleephd

Top Post Dawg
Joined
May 27, 2012
Location
Battle Ground, Wa
TDI
2002 jetta Wagon
Second image shows boost below ambiant, looks like a possible wire fault.
Something tells me you have a short to ground, or added resistance, on the map sensor somehow. Broken wire in route could be the issue, check resistance of both wires end to end.
The voltage should increase with pressure increase and decrease with less pressure reduction from what I understand.

Added resistance, or short would possibly change the output values. I would check resistance across the wires and see if I can find a way to get voltage readings while driving to see what happens with it when things are going wrong.


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Matt-98AHU

Loose Nut Behind the Wheel Vendor
Joined
Apr 23, 2006
Location
Gresham, OR
TDI
2001 Golf TDI, 2005 Passat wagon, 2004 Touareg V10.
One thing you could try is put VCDS in a place where you can see it while under the hood, just showing measuring value block 10 or 11 (not both--save bandwidth--faster reaction times for the data displayed). Then wiggle the MAP wiring at various points of the harness until you find a spot where the reading starts to jump around oddly.

If you can't find such a spot and you've basically covered everything else, it's possible the problem is with the ECM.
 

txtruck987

Member
Joined
Aug 19, 2018
Location
Houston
TDI
2001 Jetta
I messed with the wiring up to the cowl. Reading didn’t change at all. I will get under the cowl tomorrow and go at it again. I don’t have a bentley manual so I am still searching for a pinout so I can trace the individual wires, I lose them when they go into the bundle by the coolant reservoir. Thanks for yalls responses, I’ll keep you posted.

It will never go into limp mode while I am driving the car. It will only do it if the car has been turned off and back on again while warm.
 

txtruck987

Member
Joined
Aug 19, 2018
Location
Houston
TDI
2001 Jetta
Pin 1 Ground
Pin 2 AIT
Pin 3 5V
Pin 4 MAP

Correct?

I am getting no voltage out of Pin 4. Does anyone know what pin it is on the ECU side?
 

eddieleephd

Top Post Dawg
Joined
May 27, 2012
Location
Battle Ground, Wa
TDI
2002 jetta Wagon
Pin 1 Ground
Pin 2 AIT
Pin 3 5V
Pin 4 MAP

Correct?

I am getting no voltage out of Pin 4. Does anyone know what pin it is on the ECU side?
4 should be checked plugged in to see what the values coming back are. Voltage should go up with pressure. Use pinout below to check continuity.
The test pinout linked below for the raintray
http://forums.tdiclub.com/showthread.php?t=387649

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txtruck987

Member
Joined
Aug 19, 2018
Location
Houston
TDI
2001 Jetta
4 should be checked plugged in to see what the values coming back are. Voltage should go up with pressure. Use pinout below to check continuity.
The test pinout linked below for the raintray
http://forums.tdiclub.com/showthread.php?t=387649

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I appreciate the help so far.

So pulled the colored connectors on the driver's side by the ECM. The pins corresponding to the chart you linked are empty. Upon further inspection the chart states: "N/A for G/J" which I assume means Golf/Jetta. On a jetta would it be different? I am not even seeing the corresponding wire colors for the MAP sensor in the bundle.
 

eddieleephd

Top Post Dawg
Joined
May 27, 2012
Location
Battle Ground, Wa
TDI
2002 jetta Wagon
Read the line, NA G/J then stated ecu pin correlation at the end is T121/73 etc.
The color should correlate with the J/G (Jetta/Golf) which are different from the beetle that has the wires running through the cockpit connectors.

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eddieleephd

Top Post Dawg
Joined
May 27, 2012
Location
Battle Ground, Wa
TDI
2002 jetta Wagon
I appreciate the help so far.

So pulled the colored connectors on the driver's side by the ECM. The pins corresponding to the chart you linked are empty. Upon further inspection the chart states: "N/A for G/J" which I assume means Golf/Jetta. On a jetta would it be different? I am not even seeing the corresponding wire colors for the MAP sensor in the bundle.
The Jetta and Golf are the same, the beetle is different. Always read the full line when reading pinouts.
Making connector pin tools if needed
https://www.youtube.com/watch?v=bbW9Yc36RPE

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txtruck987

Member
Joined
Aug 19, 2018
Location
Houston
TDI
2001 Jetta
Read the line, NA G/J then stated ecu pin correlation at the end is T121/73 etc.
The color should correlate with the J/G (Jetta/Golf) which are different from the beetle that has the wires running through the cockpit connectors.

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I understand thanks for the clarification.

So continuity testing revealed all pins under 1 ohm

Pin 1: 0.2
Pin 2: 0.3
Pin 3: 0.3
Pin 4: 0.4

The MAP sensor to the ECM is how I tested.
 
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eddieleephd

Top Post Dawg
Joined
May 27, 2012
Location
Battle Ground, Wa
TDI
2002 jetta Wagon
I understand thanks for the clarification.

So continuity testing revealed all pins under 1 ohm

Pin 1: 0.2
Pin 2: 0.3
Pin 3: 0.3
Pin 4: 0.4

The MAP sensor to the ECM is how I tested.
I prefer to see 0 on the wires continuity wise. This is testing the individual wire end to end. May need to repin seems like a lot of resistance to me.
I have become much less resistant to wiring after making the awesome tools in the video above. The small one takes a bit more work, but, definitely worth the time.

Running 4 wires to the ECU through the cowl isn't so bad, just cut a little longer than needed and there is a lot of unused pins in the ECU connector, just need plug pins, or repair wires/pigtail plug for splicing.
Edit:
I just wanted to add a little more about the impedence of the wires being additive. On one side you have .4 ohm's and the other one is .3 ohm's equaling .7 ohm's which would throw the ecu reading off.
This impedence is the result of the wires being broken within the sheathing and likely broken somewhere causing the intermittent loss of signal to the ECM
Unfortunately this can even cause overboost due to fault signal and you don't know how much over without an accurate reading from the map.
So don't drive until fixed, unless you have an aftermarket boost gauge, still shady
 
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txtruck987

Member
Joined
Aug 19, 2018
Location
Houston
TDI
2001 Jetta
That'll be the next step then. I already have the pin tools because I needed them to replace the MAP sensor connector as it was busted. Just need the rest of it. I'll get it ordered and go from there.

Appreciate it.
 
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