Guru's Help please. A5 BRM Engine speed sensor, ECU & grounds

A5 BRM Harness Chafe ECU to engine. Many codes & G28 CkPS

On edit.: 7/27/12. Links to photos below..
1. I had multiple chafe points in my harness. The most common chafe point is the first loom clamp of the engine/trans assembly above above the starter solenoid. I, and some others had chafe further up the loom as it crossed horizontally and than runs up vertically. Each chafe point that I am aware of was at a point where the loom was clamped.
2. The BRM harness layout is such that the heavier gage conductors are in the center, or core, of the harness. The lesser gage (sensor signal and twisted pairs) are around the circumference the harness core. The harness root and size is such that it is not very flexible. The stresses, movement & weight are point loaded at the supports, ECU, and the junction near the left head (opposite side from the timing belt). The plastic of the split looms is harder then the conductor insulation. Therefore, when chafe occurs, the very small gage, .35 mm (or about 26 to 28 ga.) signal conductor’s insulation is sacrificed to the split loom and harness movement is carried by the smallest wires with the least insulation.
3. I have learned of other BEW & BRM engines which have experienced similar problems. The last count that i had was in excess of 60+ BRMs with this issue and a lesser number of BEWs. I have not established if the 2.0T &/or the 2.5 gassers have similar problems. Some have filed a complaint with the NTSB as have I.
4. I filed a warranty claim with VW; which VW promptly denied. If others are filing a similar complaint, please feel free to PM me as I will be more than happy to provide you with my file number so that you may establish a pattern. I am appealing the warranty denial (As others have said, VW’s warranty is not good for much).
5. Oilhammer's comment that the 2g28 sensor rarely goes bad is spot on. It is a bugger to access and R&R on the BEW & BRM's. If you are suspecting a problem there, you may save o lot of time by checking your harness first.
6. The BRM (or at least mine) will definitely run without the G28 signal. Apparently, as it uses the cam speed sensor as reference in the absence of the G28 crank sensor. Without the G28 sensor connected (or with a faulty signal) the start is much, much slower with an extended cranking time.
7. The Ground Points list posted in page #1 is as listed in Bentley’s. My car does not have a ground wire at every attachment point. Many ground points had multiple grounds connected thereto. Other, albeit, unused ground studs exist on the A5 platform as I found numerous such points when checking the Bentley’s listed points. The problems my car experienced were a result of harness chafe not ground point/corrosion related.
8. There was a disparity in the fuse numbering and purpose between what actually exists in my car and those shown in my owner’s manual and in Bentley’s. Bentley’s and the owner’s manual did not agree either. The owner of a similar production period A5 informed me of the same thing. I encourage every A5 owner to photograph their fuse blocks for recordation purposes.Much thanks to assistance and direction in repairing this problem to: Dan, Rich, Joe, Brian, Oliver, Jeff R., Ross-Tech, Impex and especially to Fred for this site which made this (and other past ones) repair so much easier to diagnosis & repair. A donation was made as way of thanks.
While I cannot verify it, my suspicion is that this condition had been developing for quite a while, perhaps back to about 20K. miles or so. Very occasionally, the car would very rough, almost as if it were out of time. As the condition could not be replicated and occurred occasionally, I figured it was just one of those things. The discoloration in the chafed copper conductors indicated that the condition had been developing for a long period of time. If you have concerns, your may want to voice it to VW. See Brian’s post re. the NTSB. I hope of other's sake that mine, Brian's & the others I happened into are isolated failures. But, BEW & BRM owners: Heads Up.
Similar summary posted 74 & 75. Photo links:
http://http://pics.tdiclub.com/showphoto.php?photo=52153&title=brm-ecm-harness-&cat=500
http://pics.tdiclub.com/showphoto.php?photo=52154&title=inside-split-loom&cat=500
http://pics.tdiclub.com/showphoto.php?photo=52155&title=chafed-ecm-signal-wire&cat=500
http://pics.tdiclub.com/showphoto.php?photo=52156&title=chafed-ecm-signal-wire&cat=500
http://pics.tdiclub.com/showphoto.php?photo=52157&title=chafed-ecm-signal-wire&cat=500
Original Post #1: 06.5 PD. 63.9K miles on the clock. Stock w/ RC1+ for the past 60K miles. No issues until last week.
Car ran fine. Parked for about 45 min. Restarted but a soft stall when pulling out into traffic. Immediately restarted. About 100' later oil alarm goes off. Pull to the the side, Oil level is fine. Restart. Same thing about 200 yards later, now I am watching the cluster. Just before the oil light goes off, the engines dies/misses/restarts. In trying to figure it out. Several things happen, sometimes the order varies. Start, sometimes a hard start, engine runs, flutters, tach may or may not fall to zero as the engine runs, & oil light may or may not go off. The engine is usually happy @ idle, but does not like a load. B/C not liking the load, I R&R the fuel filter. Problem remains.
Anyway, fast forward to a day or 2 later when I have time to vagcom, the code is an intermittent engine speed sensor, G28, 000802 P0322.
I run all the searches, find lots of info. To make a long story short. The most similar fault pattern resembled that in the A4, BEW ECU flash & additional ground wire threads. So, I swap out the battery with a known good one, w/ a charge topped off >13. VDC. 14+ VDC when running. Check & clean the grounds in the engine bay. Problem remains. I did run across this thread: http://forums.tdiclub.com/showthread.php?t=235472 & called Impex who told me that the speed sensor shows that it was superceeded. So, while I know that Oilhammer has posted that these are not a high failure item, I purchased & installed one. When apart, the connections, harness, etc. all looked good. No visible chafe points, corrosion, etc.
Unfortunately, the problem remained. I go back & recheck the grounds & go up into under the cowling this time to check those grounds. The ECU does not appear to have a separate ground. Rather, it appears to be using it's metal bracket as the ground path. The ground stud @ the right (passenger) side does not have anything attached to it but is listed in Bentley as a ground point. Bentley also lists a ground @ the right cylinder head that I am unable to find.
Currenly, I am getting 1 of 2 codes and a randomly alternating basis: 1) 000802, Engine Speed Sensor, G28, P0322, No, or intermittent signal, V14.44 & 2) 000801, Engine Speed Sensor, G28, P0321, implausible signal, V10.76V.
Has anyone run into this yet on a BRM? Any information on hidden ground points that are not in Bentley? about the pass. side ground stud w/ no wire? ECU ground path? Any hidden grounds under the battery tray (as is on the A4)? Relay problems that I am unaware of?
At this juncture, I am inclined to install a new/additional ground from the ECU bracket to the ground stud drivers side near the strut. Thanks in advance for any info.

Grounds

Grounds on 06 jetta:
1. engine comp, top of right front chassis member, underneath headlight
2. passenger comp, base o A-pillar, behind trim
3. connection at right end of cylinder head
4. battery to chassis, under engine hood, near battery
5.right side of trunk, on inner wheel housing, behind trim
6. left side trunk on C-pillar, behind trim
7. left side trunk,on inner wheel housing, behind trim
8.engine/transmission ground, on top of left front chassis member
9.in plenum chamber, next to right strut tower
10.engine compartment, on top of left front chassis member
11.in plenum chamber, next to left strut tower

Yes, I have had problems with this. Does you car crank for longer time before it starts? Are there times when the tach is not working? Let me know I have more info. Is was a harness problem on the car I fixed.

Check on the grounds. My Bentley also lists a #12. Om plenum chamber, next to the left strut tower. That is the one that does not have anything connected. I read nothing for the ECU. After reading the search result on the BEW problem w/ similar symptoms, I am a bit worried.
Re: the starts, there are 2 typical patterns.
1. Normal start. Tach works, but engine misses & will stall
2. Often the cranking time is longer. I can watch the tach, it will be bouncing about 300 +/-, them will drop to 0, about 1 to 2 seconds later it will start & run. At this start pattern, I will get the oil alarm, flashing oil light, temp light & glow plug light which alternately flash.
On edit: After reading Joe's & Fixes post. I started the car this AM. A jiggle test on the harness showed two things.
Start type #1: A harness jiggle along the harness run from the block near the oil filter along to the wire tray under the air filter box & ground screws will immediately stall the engine. This occurred several times.
Start type #2: Harness jiggle has no noticeable effect. Engine remains running.

Have you checked your lift pump?

Negative on the lift pump. several reasons. I R&R the filter, the restart was excellent, I did crude volume test @ the filer feed, & the G28 codes which are point elsewhere, & the miss/stutter is so quick, it "feels" electrical vice fuel. In the absence of the G28 codes above, I would be into the lift pump.

Ran into this before .. The Cam position sensor and the engine speed sensor share the same ground .. The center pin on either is the ground ? Will have some more info after I do some more research .. R

I'm having the same problem... they replaced the sensor 1 month ago, needless to say, it's back......

Interesting, so is this might be a bit more than isolated. Brian, how many miles on your car?

59,000. Both times it happened to me were in wet conditions

Bone dry for me when it occured. But, recently the roads had been salted. Makes me wonder. All the grounds that I have cleaned looked pretty good.

For the record, here's my cars status:
All of a sudden I got 3 chimes and the check engine light came on solid, the tach stopped working, the glow plug light and the oil light started flashing, and the traction control is locked off with that light on as well.

I'd like to see what joetdi has to say....

Fix's input will be helpful as well. I have been over the harness. It appears to be continuous from the engine to the ECU. No visible problems. I have not fully figured out the ground path yet and cannot find the ground @ the right side of the head.

right side, meaning drivers or passengers side? I have a rotating connector with 5 or 6 wires on it...looks like thats a sensor too.

My understanding is that Bentley's refers to the sides from looking forward. Right side = Passanger side.

The large round connector on the driver's side (car left) is carrying power to the solenoids for the injectors. The ground path for the solenoids is through a return wire to the ECU ground, in the same connector.

I do not have a manual for the A5's, but there is no head ground on the A4's, except the ground through bolts to the block. So the glow plug's ground path is through the block, to the transmission, and then to the large ground wire that runs to the negative terminal on the battery and is grounded to the body on the way.

I need to borrow an A5 manual.

Dan

status update

I left the car in the garage overnight with he hood open. It started and runs fine now, but the engine light is on solid.

Brian; Do you have Vagcom access? If so, what codes are you showing?

No Vagcom here... And after looking over the repair bill, they failed to note the code from the original service.

The Vagcom code the dealer got in January was p0322

P0322 Engine Speed circuit input no signal. (<75 rpm).

If this is really out of service an ALH will use the needle lift sensor as a backup, and will continue to run (it is not clear if it will start without the engine speed sensor.) The BEW PD has no backup (even though it tracks the CAM speed as well!) and will not run.

My Engine speed sensor (2005 BEW PD) reads 561 ohms pins 1-2,or pins 2-1 (polarity made no difference). The repair manual calls for "0.7 to 1000K ohms" across pins 1-2. Like I said, I had 561 ohms on a known good one. The repair manual also has you check that there is an open circuit between pins 1-3 and 2-3, expecting infinite ohms. My fluke read greater than 6 megohms.

While I suspect the same sensor is used on the BRM, I do not know for sure.

Another status update

Car is back to normal and the check engine light went out. The grounds look good, but I have to put my money on a harness \ connector problem. I didn't get a scan yet, I'm trying to find someone who is local with Vag-com who can help.





Also, Dan, mine was running after the failure. It was running poorly. I've heard the term "Limp mode" used.

Brian/Bob I sent one of you a PM, but use an ohm meter and check the wires that go to the speed sensor to the ECM at the ECM. As you watch the ohm meter wiggle the wire harnesses down by the starter and see if it changes. I have found broken wires in the harness near the starter area, twice now.

Brian/Bob I sent one of you a PM, but use an ohm meter and check the wires that go to the speed sensor to the ECM at the ECM. As you watch the ohm meter wiggle the wire harnesses down by the starter and see if it changes. I have found broken wires in the harness near the starter area, twice now.

My point was that if the engine speed sensor had failed completely, you would not be running.

So it was more likely to be an intermittent wiring issue, than a totally failed sensor.

Bob, I may not be able to get to mine just yet, but will share results as soon as I have them.

DanG144 said:

My point was that if the engine speed sensor had failed completely, you would not be running.

So it was more likely to be an intermittent wiring issue, than a totally failed sensor.

Click to expand...

Dan; My understanding is that the ECU is picking up the Cam Sensor & disregarding the Crank sensor which allows it to run, but leaves the Tach @ O.

My sense is that you are correct on the intermittent wiring issue. I have looked for the head ground and not found it. I have also spoken to a very knowledgeable TDI Guru who has done cams & Tbelts on the BRM and has never noticed a ground point on the head. This, and the vacant ground point in the right plenum, leaves me to conclude that the ground list in Bentley's is more a generic list of grounds.

Do you happen to have any details on the A4, BEW similar symptom TSB and ground issues?

Your car will start and run without the crankshaft sensor. You will loose the tach however. Your crank time to start will be longer when it is not working though, because it has to use the camshaft sensor to find when to start injection. The tach runs off the crank sensor. I've been there already a couple years ago.

I defer to Joe on your car.

For a 2005 BEW:
I can say that the repair manual indicates that a BEW will not run with the crank sensor signal unavailable.

I can further verify that my BEW will NOT start with the crank sensor unhooked. It will give you:


Address 01: Engine
Control Module Part Number: 038 906 016 Q
Component and/or Version: R4 1,9L EDC G000SG 6110
Software Coding: 0150031
Work Shop Code: WSC 00066
1 Fault Found:
16706 - Engine Speed Sensor (G28): No Signal
P0322 - 000 - -
Freeze Frame:
RPM: 0 /min
Torque: 0.0 Nm
Speed: 0.0 km/h
Load: 0.0 %
Voltage: 10.56 V
Bin. Bits: 00101100
Idle Stabilization: 0.0°KW
RPM: 126 /min

I can further verify that when the signal is lost while running on my BEW the engine dies immediately, AND IT GAVE NO ERROR CODE.

sensor Pin 1 to 2 or 2 to 1 is 561 ohms
Sensor pin 1 or 2 to 3 is more than 6 Megohms

With the ECM end still hooked up the cable to the sensor gives:
Key ON
pin 1, 2.5 vdc
Pin 2, 2.5 vdc
pin 3, 0.0 vdc

Key off
pin 1+ to ground -, gives 53.26 k ohms
pin 2+ to ground -, gives 53.26 k ohms
pin 3+ to ground -, gives 0 ohms

I can see no external ground wire from the head.

Pin 3 of the crank engine speed sensor is shown as going to a ground, and the resistance measurement I took shows that it very likely does. I do not know where the ground is located.

Drawing series 81/5 is apparently in error in at least one respect: it shows wire 2 connected to wire 3 (between the plug and the ECM) at wiring connection 200 (but, unusually, does not indicate where wire connection 200 is). My wire 2 and 3 are definitely not connected, as the resistance measurements above show. I suspect that someone saw that wire 3 goes to the shield on wire 2 (which is also shown on the wiring diagram.) and thought it was the center conductor. The drawing in my Bentley and my erWin copy of the drawing show the same thing.

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