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Audi OBD II 16706 - Engine Speed Sensor (G28): No Signal - Troubleshooting help!!


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Last Post: Mar 24, 2016 12:54 PM Last Post By: JorG
99.5VR6

Posts: 4
Registered: 12/28/04
16706 - Engine Speed Sensor (G28): No Signal - Troubleshooting help!!
Posted: Mar 27, 2005 9:50 PM
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I have a 1999 MK IV Jetta - it wont start. When I scanned it with my Vag Com the following codes were stored:

1 Fault Found:
16706 - Engine Speed Sensor (G28): No Signal
P0322 - 35-00 - -
I have checked the Sensor For continuity etc. per the Bentley Manual and nothing seems to be wrong but the car still won't start.

Is there any more testing that can be done to determine if there is a problem with the sensor or the wiring harness?

Anybody else out there experiencing a similar problem?

Any Ideas?
fast928

Posts: 4,192
Registered: 03/01/02
Re: 16706 - Engine Speed Sensor (G28): No Signal - Troubleshooting help!!
Posted: Apr 23, 2005 4:54 PM   in response to: 99.5VR6 in response to: 99.5VR6
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If you haven't already, I would suggest you post this down in the VW forums.
dr_rigo

Posts: 2
Registered: 03/16/06
Re: 16706 - Engine Speed Sensor (G28): No Signal - Troubleshooting help!!
Posted: Mar 16, 2006 12:44 PM   in response to: fast928 in response to: fast928
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hey i got a 96 audi and im having the same problem,i have codes _po322,p1340,and p1392,i changed cam and crank sensors right after i was done and it didnt wanna start..i was under the car so i might as well change the coolant, when i was done it started right up, and it worked fine for about a week and than it started throuwing the same code back again p0322.i took it to a mechanic and he said those to sensors were working fine that it needed a computer,,so i went and bought a computer and it still did the same thing,it started fine when cold, but when it gets to normal operating temperature and dont wanna start,i have to wait 1 to 2 hours,,well i been readying this forums and i seen that a couple people have problems with theyre coolant temperature sensor,it doesnt start when its hot,i think thats the problem on my car because the gauge flactuates it goes from cold to the middle than comes back down..if you also know what else could be wrong with it please let me know.. thanks
Port Fellamay

Posts: 4,105
Registered: 01/18/04
Re: 16706 - Engine Speed Sensor (G28): No Signal - Troubleshooting help!!
Posted: Apr 4, 2006 5:55 PM   in response to: dr_rigo in response to: dr_rigo
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The engine speed sensor is a reference sensor, and like the abs sensors, there's a wheel that rotates for the sensor to pick up on and judge distance. If it's too far away from this wheel it won't work, or if it's dirty, or if it's loose or damaged. I am dealing with this problem right now, though it's intermittent, it also seems to be causing an intermittent misfire in the ignition system, since the reference sensor is part of the ignition control.

Think of it sort of as an old distributor from a 16v VW, and the hall effect is not working, but the sensor likely isn't the problem most times if the resistance is in spec and the wiring has continuity no visible signs of damage. Without the reference signal no the car won't start or will misfire if the flywheel reference signal is weak.

I'm thinking the transmission itself may have an impact if the fluid is not at the proper level, it doesn't run as intended because of hydraulic pressure, and the calculated reference timing is off.
Art

Posts: 2,743
Registered: 09/08/00
Re: 16706 - Engine Speed Sensor (G28): No Signal - Troubleshooting help!!
Posted: Apr 4, 2006 9:49 PM   in response to: Port Fellamay in response to: Port Fellamay
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Gentlemen,

Don't go making a mountain out of a mole hill!

On almost all VW & Audi vehicles with various versions of Bosch Motronic M2.9, M5.9, and ME7.x (and other non-USA versions), that G28 DTC will always be there if you switch on the ignition, but don't start the engine. Does it mean that something is wrong? Probably not.

Read what the DTC says, "no signal". Of course not; the crankshaft is not turning, so there can't be a signal. When the crankshaft turns, the G28 gets a signal and the engine starts. Period. The DTC self-erases if/when everything is OK.

Think your G28 is defective? Hook up your scan tool, go to measuring value blocks, and find a display group that shows RPM. Crank the engine. If you read RPM, the G28 is good.

In OBD terms, G28 is called an RPM sensor, but it is actually is a speed and reference sensor in most applications.

Take that VR6 as an example. A rotor wheel is attached to the crankshaft. It has space for 60 "teeth", but there are only 58 and a 2-tooth gap. The G28 is a magnet wrapped in wire and every time a tooth passes, a small A/C voltage is induced. So the computer "sees" 58 nice little voltage spikes and than a short space and 58 more, and so on. So the speed part is the 58 teeth, and the reference part is the gap.

Where am I going with this, and why? The speed part runs the engine, of course, but why the reference? Because the ECM needs to "know" TDC for cylinder #1. When the ECM "sees" the gap, it could be cylinder #1 OR cylinder #6 since BOTH pistons are up. The ECM "looks" at the G40 Camshaft Position Sensor (CMP) to "see" if a signal is present because the camshaft(s) turn at half crankshaft speed. Since there is only 1 window in the shutter wheel and it corresponds to cylinder #1, if it "sees" a signal, it's got #1; if it does not "see" a signal, it's got #6.

Got it? The G28 is an inductive sensor. The G40 is a Hall sensor. What happens if there is no G40 signal? The engine will still run. But that is a topic for another time.

So hook up the scan tool and look for a display group (001) with RPM.

Port, you lost me on that explanation and the transmission references. G28 has NO connection with the transmission during normal operation.

Arthur LeBrun
Bentley Publishers.

PS - Buy our book. Dan and I wrote most of it a couple of years ago.
http://www.bentleypublishers.com/product.htm?code=vu23
Port Fellamay

Posts: 4,105
Registered: 01/18/04
Re: 16706 - Engine Speed Sensor (G28): No Signal - Troubleshooting help!!
Posted: Apr 5, 2006 12:18 PM   in response to: Art in response to: Art
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Anyhow you explained it best Art, here's the dilema, the car has Intermittent Implausible G28 signal, and neither that nor the misfire codes will clear. I checked the sensor wiring out, and swapped coils, and it still is the same codes. There's also a code for clutch circuit, so I was thinking maybe drag from the trans had something to with it. But mainly I thought the evidence was circumstantial and the car needed a tune up.

I think I was right, I replaced the plugs and it runs a lot better. I adjusted the throttle cable, it's definately more responsive, and the brake switch error has disappeared. I think that new O2 sensors should do the trick to resolve the problem completely. The thing that puzzles me though is the computer doesn't seem to want to clear the codes, either running or with the ignition simply on. I'd hate to say there's something wrong with the computer, but that is one of the resolutions to the Implausible signal code, replace ecu.

Another thing is that it's reporting the misfire on 3 & 7 cylinders error twice which I find odd.
Port Fellamay

Posts: 4,105
Registered: 01/18/04
Re: 16706 - Engine Speed Sensor (G28): No Signal - Troubleshooting help!!
Posted: Apr 11, 2006 9:06 PM   in response to: Port Fellamay in response to: Port Fellamay
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So guys I fixed the codes, the spark plugs did the trick for the misfire. The A8 D2 seems to throw a different code than vag-com lists on their page when checking unstarted. The misfire codes are gone, the misfire gone. Did the O2 sensors, and they were a pain in the neck. Everyone remember to do you O2 sensors at 90k cause if they get siezed in there, you might have some unneeded problems.

3 were easy, had to drop the cat to get the drivers side one off it, and it didn't want to let go of it. Even heated up with a torch it wouldn't budge. By the time it got hot enuff to come out, the O2 sensor had actually melted like a soft weld into the cat holes. Had to retap it...problem solved..next time service is needed, the cat will probably need to be replaced, so I'm not worried.

I also had cleaned the rpm sensor connector with alcohol. So I dunno somehow these repairs seem to work out the next day and problems solved.
Jason O

Posts: 1
Registered: 10/04/06
Re: 16706 - Engine Speed Sensor (G28): No Signal - Troubleshooting help!!
Posted: Oct 4, 2006 5:14 PM   in response to: Art in response to: Art
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I guess this is a kinda old post but i am having a problem with my car shutting off when it gets to normal temps and will not start until it cools. The only code i get in my vag com is this sensor. I tested the sensor in the measuring blocks and i do get an rpm reading when the car is cool and starts but nothing when its warm and not starting. Does this sound like it can be the sensor even getting the reading when the car is started? If this seems normal what else should i check.. i get no other dtc's.
audiqv8

Posts: 211
Registered: 05/21/04
Re: 16706 - Engine Speed Sensor (G28): No Signal - Troubleshooting help!!
Posted: Oct 5, 2006 2:32 PM   in response to: Jason O in response to: Jason O
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Great write up Art.

"it started fine when cold, but when it gets to normal operating temperature and dont wanna start,i have to wait 1 to 2 hours"

These sensors are magnetic sensors as Art have already pointed out. The rpm sensor produce an AC current as the teeth passes over the sensor, but as we all remember from high school physics "A magnet loses it magnetic properties once it get hot". This will explain why the engine will not start until it has cooled down, the signal is missing with a hot engine,
DEANB

Posts: 1
Registered: 07/24/06
Re: 16706 - Engine Speed Sensor (G28): No Signal - Troubleshooting help!!
Posted: Jan 23, 2007 4:06 AM   in response to: 99.5VR6 in response to: 99.5VR6
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hi
vr6 golf 1995
an error code 00513 speed sensor no signal (g28)
there is no spark .i have checked for continuity-ok
no rev-counter under measuring blocks
maybe i must check for continuity to ecu
new sensor fitted,still no spark
pls help
thanks
newkid70

Posts: 1
Registered: 02/05/07
Re: 16706 - Engine Speed Sensor (G28): No Signal - Troubleshooting help!!
Posted: Feb 5, 2007 3:14 PM   in response to: 99.5VR6 in response to: 99.5VR6
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Replace the sensor. We have seen a few bad sensor that reads correct.
barrettn

Posts: 2
Registered: 08/25/04
Re: 16706 - Engine Speed Sensor (G28): No Signal - Troubleshooting help!!
Posted: Mar 27, 2007 9:22 PM   in response to: Art in response to: Art
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Hi i have an Audi 80 2.6 1995 Quattro that had a bit of a hit in the r/h front and now has no signal from G4 and G40, I have tested the G4 sendor and it is working also i have noticed that there is no power to engine timing fuses i and 2 with ignition on or when cranking, when tested with scan tool in measuring block 1 there is no rpm recorded when cranking.. is there a control relay?? i thought G4 would signal direct to control unit, i have swaped control units and replaced the G4 and still nothing.. any help would be much appreciated
Cheers Nick
JorG

Posts: 1
Registered: 03/23/16
Re: 16706 - Engine Speed Sensor (G28): No Signal - Troubleshooting help!!
Posted: Mar 23, 2016 3:33 PM   in response to: Art in response to: Art
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I know this is an old post, but I don't want to create a separated one for the same topic.
I'm running in to something similar.

I have a 1995 VW Golf III 2.0 with a no start condition. It cranks ok but no RPM on VCDS, no injector pulse and no spark, the distributor hall-effect works ok (not that it would matter), but G28 Engine speed sensor doesn't produce a signal when connected to the engine harness, if I disconnect it, the sensor works fine(because it produces its own voltage), and shows a good looking waveform signal, so I tough I would have a short to ground on one of the wires going to the ecm, but I don't, both wires are good(not shorted to ground, power, or themselves).

I've checked powers and grounds to ecm and they are all ok, so I changed the ecm and everything is the same( not working).

With G28 sensor unplugged, key on, on the harness side, I have ground on two pins and 5 volts on another. Shouldn't I have 5 volts on the two wires that go to the ecm, and an external ground ?

My conclusion is that the ecm is "grounding" the signal that the sensor produces, but this is the second ecm.
Any suggestions?

I don't know if it matters, but ecm's numbers are a bit different :

Old ecm part no. 037 906 258 AH
New used ecm part no. 037 906 258 AA

Thank you for your time and insight guys.

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