ATL Engine crank shaft sensor error (P0726)

Andris

New Member
Hello,
I have a bumble bee (Audi A2 Colour Storm Imola Yellow 2004), and I have a problem with a crank shaft sensor.

Few years ago I had this error, replaced sensor and problem was solved, but about a year later error returned, and after sensor replacement problem is still there, replaced another sensor from different manufacturer - did not help.

No problem when starting engine, error show up after ~3000 rpm and show "check engine" and another indicators is on, and rpm goes down, but engine still works.

Interesting fact: if sensor bolt is not tightened no error engine runs smoothly, if tightened then error over 3k rpm.

What is done :
Replaced G28 sensor x2
Replaced G40 (cam shaft) sensor
Replaced G28 wire and connector (Shielded cable 3wire)

Please help.
 

audifan

A2OC Donor
Perhaps the answer is to have a proper scan done on the car such as VCDS rather than something generic that may well be of little use.
 

audifan

A2OC Donor
Firstly make sure everything is tight then run a full scan on the car. Depending on what faults picked up, clear the faults but do not rescan. Shut the car off and disconnect VCDS. Take the car for a 15 minute drive then rescan using VCDS. Come back with the faults. By all means you can check through the various measuring blocks of the engine but until we know what VCDS has reported it is guess work.
 

Andris

New Member
Dmf original?
Wear or imbalance exaggerated with revs potentially

I don't have any information about change before I bought the car, currently my A2 have 288k km (bought with 255k km).
Is there any way to check/test DMF without removing gearbox?
 

Olerype

Member
I would say your problem has nothing to do with DMF; but in my case with worn DMF the car was not happy being driven in the 1200-2000rpm range (excess vibrations)

That everything is OK with the bolt not tightened appears suspicious to me, is it the same if you also disconnets the sensor?
 

Dave M

Well-known member and A2OC Donor
Are you fitting a genuine VAG cam sensor for an ATL. 🤔
 

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Andris

New Member
Firstly make sure everything is tight then run a full scan on the car. Depending on what faults picked up, clear the faults but do not rescan. Shut the car off and disconnect VCDS. Take the car for a 15 minute drive then rescan using VCDS. Come back with the faults. By all means you can check through the various measuring blocks of the engine but until we know what VCDS has reported it is guess work.
I do not have full version of VCDS, and I scan only ECU.
VCDS shows a bit different error codes than mobile application via Bluetooth.

Code:
Control Module Part Number: 045 906 019 F
  Component and/or Version:  1,4l R3 EDC 0000SG  5418
           Software Coding: 00002
            Work Shop Code: WSC 02138
                      VCID: 18434B636B8B
           Additional Info: WAUZZZ8Z15N008765     AUZ7Z0D2679938
1 Fault Found:
16705 -  Engine Speed Sensor (G28): Implausible Signal
        P0321 - 35-10 -   - - Intermittent

on phone error code is P0726

error is not there all the time shows up only if rpm more than ~3k
 

Andris

New Member
The Ross-Tech site has further details on this code that may help: http://wiki.ross-tech.com/wiki/index.php/16705/P0321/000801

Possible Symptoms​

  • Engine shuts off
> Engine is not shutting off, rpm drop but not completely if continue press acceleration pedal goes up until ~3k rpm and drops again.
  • Engine doesn't start
> Engine starts normally, if disconnect connector engine does not start
  • Speedometer inoperative
> no problem
  • Glow Plug Indicator Lamp (K29) flashes
> yes, indicator blinking after 3k rpm, and until error clearing.

Possible Causes​

  • Engine Speed Sensor (G28) loose
> when G28 bolt is loose engine works normally, if tightened - problem returned.
  • Engine Speed Sensor (G28) faulty
> wires changed, connector changed, sensor changed twice from different manufacturer

Possible Solutions​

  • Check Engine Speed Sensor (G28)
> Done.
 

audifan

A2OC Donor
OK. Firstly are you using the correct crank sensor and not a pattern part. Second are you using the correct size bolt to secure the sensor? Third is there a washer under the bolt head?
 

audifan

A2OC Donor
If the flywheel and the sender ring behind it has been disturbed, the sender ring needs to be replaced if its securing bolts were removed. If this is the issue the sender ring may now be warped causing the sensor issues.

Recheck the wiring.
 

audifan

A2OC Donor
That sender ring does not look good. It is probably distroted out of round and when the sensor is tightly bolted in it is hitting the sender ring.
 

audifan

A2OC Donor
If every tooth on the sender ring was damaged I would say that the incorrect length sensor had been fitted. If only some teeth are damaged when the correct sensor it torqued then there is a lack of clearance between the sensor an individual teeth hence the sender ring is either distorted or unlikely loose.

Unfortunately to check this you would need to insert a dti into the sensor location and rotate the engine looking for run out distortion. If found the gearbox, clutch and fly wheel will have to be removed for access to the sender ring.
 

audifan

A2OC Donor
Not a dumb question at all

A dti is a Dial Test Indicator....

1662565867219.png

The lower end of the indicator is inserted into the hole for the crank sensor until it makes contact with one of the troughs between the teeth. Rotate the engine by hand until the indicator is on one of the peeks or teeth and zero it. Now slowly rotate the engine by hand and note the readings for each tooth they should all be the same ( within a fraction or two ).

You may need a dti with a longer probe to allow full depth and clearance from the engine block above picture was just to illustrate a dti.
 
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