SDDane

Hi - this is my first thread here, got serious problems, I hope someone can help with idea on troubleshooting..

2001 Allroad running fine, untill one day (200 feet from home luckily) it nearly stalls, I pull over, throttle is very uneven fluctuating +- 3-400rpm. ABS, ESP, Levelcontrol and MIL lights comes on shortly after each other.

Pull codes:

17866 - Exhaust Gas Temp Sensor 2 (G236): Short to Ground
18010 - Intermittent
17704 - Intermittent
17869 - Exhaust Gas Temp Regulation for Bank 1: Implausible Signal
P1461 - 35-10 - - - Intermittent
16487 - Intermittent
17965 -
Readiness: 0000 0000

So I change the driverside EGT sensor and MAF and reset codes. No change - I pull the codes:

Now:
Address 01 -------------------------------------------------------
Controller: 4Z7 907 551 K
Component: 2.7l V6/5VT G 0001
Coding: 06752
Shop #: WSC 02325
WAUYP54B21N049774 AUZ7Z0Y1567485
1 Fault Found:
16487 - Mass Air Flow Sensor (G70): Signal too High
P0103 - 35-10 - - - Intermittent
Readiness: 0110 1101

Address 02 -------------------------------------------------------
Controller: 4Z7 927 156 A
Component: AG5 01V 2.7l5VT USA 1414
Coding: 00002
Shop #: WSC 00000
1 Fault Found:
18265 - Load Signal: Error Message from ECU
P1857 - 35-10 - - - Intermittent

Address 03 -------------------------------------------------------
Controller: 4Z7 907 389
Component: ABS/ESP allrad D47
Coding: 06397
Shop #: WSC 02325
1 Fault Found:
18265 - Load Signal: Error Message from ECU
P1857 - 35-10 - - - Intermittent

Address 08 -------------------------------------------------------
Controller:
Note: Excessive Comm Errors

and from Lebel control module:

1 Fault Found:
01316 - ABS Control Module
79-10 - Please Check Fault Codes - Intermittent

Did throttle body adaptation, no change.

Idle CAN be steady, but as soon as I as much as touch the throttle, fluctuation kicks in - engine almost stalling, revving to 1200RPM. When trying to hold a higher RPM ~3000RPM a little more steady bu still RPM fluctuations. When test driving - same thing and shuddering acceleration (kind of surging).

Error codes are now steadyly comming back of course after clearing

Please help.. any ideas out there..?

Thanks in advance

Rally_nutcase_1982

1. Check hose setup of crankcase ventilation for secure seating and proper seal.

2. Check Mass Air Flow (MAF) sensor -G70

Mass Air Flow (MAF) sensor -G70-, checking

Note:

Read measuring value block display group 2 as described in repair manual and evaluate it Page 01-108 . If the suggested repair steps refer to the voltage supply test for the Mass Air Flow (MAF) sensor or the wiring connections from the Mass Air Flow (MAF) sensor to the Engine Control Module (ECM), proceed to the following pages.

Please note the distinction between Mass Air Flow (MAF) sensors made by Bosch and those made by Hitachi (recognizable via the writing on the sensor).

Voltage supply for Mass Air Flow (MAF) sensor, checking (Hitachi MAF sensor)

Note:

For Bosch Mass Air Flow (MAF) sensors Page 24-70

- Disconnect connector from Mass Air Flow (MAF) sensor.




--------------------------------------------------------------------------------

24-67


- Connect multimeter to terminal 2 of connector and engine Ground (GND) for voltage measurement.

- Operate starter briefly.

Specification: approx. battery voltage

Note:

Voltage is supplied to Mass Air Flow (MAF) sensor from Fuel Pump (FP) relay.

If there is no battery voltage.

- Check wire connection from terminal 2 of connector to Fuel Pump (FP) relay via fuse for open circuit and short circuit to Ground (GND), repair if necessary.

Repair Manual, Electrical Wiring Diagrams, Troubleshooting & Component Locations



--------------------------------------------------------------------------------

24-68


- Connect multimeter to terminal 2 and terminal 3 of connector for voltage measurement.
- Operate starter briefly.
Specification: approx. battery voltage

Note:

Ground (GND) from the ECM is present at terminal 3 of connector.

If specified value is not obtained, check wire connections Page 24-69 .

- Connect multimeter to terminal 3 and terminal 1 of connector for voltage measurement.
- Switch ignition on.
Specification: approx. 5 volts

If specified value is not obtained, check wire connections Page 24-69 .




--------------------------------------------------------------------------------

24-69


Wire connections for Mass Air Flow (MAF) sensor, checking (Hitachi MAF sensor)

Note:

Signal wire is also checked during wire test.

- Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM Page 24-20 .

The following wire connections must be checked for short circuit to B+, Ground (GND) and for open circuit

Connector for Mass Air Flow (MAF) sensor -G70-
VAG1598/31 test box terminal

1
53

3
27

4
29





--------------------------------------------------------------------------------

24-70


Voltage supply for Mass Air Flow (MAF) sensor, checking (Bosch MAF sensor)

- Disconnect connector from Mass Air Flow (MAF) sensor.
- Connect multimeter to terminal 2 of connector and engine Ground (GND) for voltage measurement.
- Operate starter briefly.
Specification: approx. battery voltage

Note:

Voltage is supplied to Mass Air Flow (MAF) sensor from Fuel Pump (FP) relay.

If there is no battery voltage.

- Check wire connection from terminal 2 of connector to Fuel Pump (FP) relay via fuse for open circuit and short circuit to Ground (GND), repair if necessary.
Repair Manual, Electrical Wiring Diagrams, Troubleshooting & Component Locations



--------------------------------------------------------------------------------

24-71


- Connect multimeter to terminal 2 and terminal 3 of connector for voltage measurement.
- Operate starter briefly.
Specification: approx. battery voltage

Note:

Ground (GND) from the ECM is present at terminal 3 of connector.

If specified value is not obtained, check wire connections Page 24-72 .

- Connect multimeter to terminal 3 and terminal 4 of connector for voltage measurement.
- Switch ignition on.
Specification: approx. 5 volts.

If specified value is not obtained, check wire connections Page 24-72 .




--------------------------------------------------------------------------------

24-72


Wire connections for Mass Air Flow (MAF) sensor, checking (Bosch MAF sensor)

Note:

Signal wire is also checked during wire test.

- Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM Page 24-20 .

The following wire connections must be checked for short circuit to B+, Ground (GND) and for open circuit

Connector for Mass Air Flow (MAF) sensor -G70-
VAG1598/31 test box terminal

3
27

4
53

5
29





--------------------------------------------------------------------------------

24-73


Wire resistance: max: 1.5 Ohm

- Also check all wires for short circuit to each other.

Specification: infinite Ohms (no continuity)

- If voltage supply and wire connection are OK, replace Mass Air Flow (MAF) sensor -G70-.




--------------------------------------------------------------------------------

24-74


Air system for leaks (un-metered air), checking

Check with engine leak detector spray G 001 800 A1

CAUTION!

Part numbers are for reference only, always check with your parts department for latest information.

Note:

The vacuum in the intake system will cause the leak detector spray to be drawn in with the outside air. The leak detector spray reduces the combustibility of the mixture. This leads to a drop in engine speed and to a significant increase of the CO content.

The safety precautions listed on the container must be adhered to.

- Connect VAG1551 (VAG1552) and select engine electronics control module with "Address word" 01. Engine must be running at idling speed. (Connect scan tool and selecting engine electronics control module Page 01-8 .)

Rapid data transmission HELP

Select function XX

Indicated on display

- Press buttons -0- and -8- to select function "Read Measuring Value Block" and confirm entry with -Q- button.

Read Measuring Value Block

Enter display group number XXX

Indicated on display




--------------------------------------------------------------------------------

24-75


- Press buttons -0-, -0- and -1- to select "display group number 001" and confirm entry by pressing -Q- button.

Read Measuring Value Block 1

1 2 3 4

Indicated on display (1...4 Display fields)

- Note engine speed in display field 1.
- Systematically spray parts of intake system with engine leak detection spray.

If the engine speed does not change:

- Press button.
- Press buttons -0- and -6- to select function "End Output" and confirm entry with -Q- button.

If the engine speed drops:

- Press button.
- Press buttons -0- and -6- to select function "End Output" and confirm entry with -Q- button.
- Check sprayed areas of intake system for leaks and repair if necessary.

IL_Allroader

near Chicago?

:-)

Rally_nutcase_1982

since you have a VAGCOM, this electronic data base is a big help in researching things for DIY's. So perhaps buying one wouldn't be a bad idea.

They are usually listed on ebay, just search for the allroad repair manual. Or you can pick one up directly from Bentley Publishers.

SDDane

Thanks for the help.

I tried these steps before replacing the MAF which by the way was a Hitachi. Only thing that did puzzle me was that the 5V supply was present both with the ignition OFF as well as ON. I tested for shorts between the wires and found none. I had no clue as how to measure the wire resistance (spec'ed at 1.5Ohm max), if you can clarify how to do that, I'd be happy.

I will check crankcase connections once again. I did not meticulously check vacuum leaks, but did change one hose. Note that this error came out of the blue sky, and not as a slowly progressing failure. One minute running perfectly, the next - a lit up x-mas tree.

I do have VagCom, but none of the VAG tools referenced in the repair manual. I am NO whizzard with the VagCom.

Again thanks so much for helping out...I may have to surrender to the dealer on this one..

Rally_nutcase_1982

thing that you can test just for the sake of data collection, or a shot in the dark: Misfires from each cylinder. For that, you'd need a second person monitoring the VAG while driving.

Did you unplug/reconnect the ECU to see if it got lose, with so many comm errors I'd check the Hardware.
Not sure if your is chipped, but there were faults like yours coming from soldering points getting lose. So remote troubleshooting is a bit painful and there are thousand possibilities.

One small problem, I don't have my VAG here so I'm not sure which measuring blocks will show that; try 015/016 or 115/116 or just walk your way up.
Perhaps some of the guys here can chime in? Please ;-)

want

connection and the connector for the MAF sensor. Hope this is not caused by a bad ECU.
What are the MAF reading, measuring block 002, when at idle and when you touch the throttle?

want

By the log func of VAG-COM, you will do not need a second person monitoring the VAG while driving.

quickaudi:STFA

2nd. Bad wiring, burnt through wiring. Should also disconnect MAF and see if it's better.

Rally_nutcase_1982

I'm always afraid of the unknown to happen like having to make avoidance moves or emergency braking. The laptop would fly from the passenger seat or worst ;-)