DTC P000B - Camshaft Position Slow Response (Bank 1)

Everyone loves a happy ending. Share your diagnostic success stories here.
Post Reply
User avatar
Rfmotors1
TwoWaves
TwoWaves
Posts: 86
Joined: Fri Aug 31, 2012 8:14 am

DTC P000B - Camshaft Position Slow Response (Bank 1)

Post by Rfmotors1 »

Camshaft adjustment intermittent malfunction:
DTC P000B - Camshaft Position Slow Response (Bank 1)

The Diagnostic Technician world is often very different with many limitations compared to ideal world described in workshop manuals and diagnostic classroom trainings. This case study describes the step by step as how we have carried out the diagnostic procedure on the quad camshaft “V” engine design from VAG family. This is one older case study I have written few years ago somewhere at 2015 but I think it is interesting enough to share.
The car was in another workshop I have visited and we had only half day to collect all the data and information, the workshop had manufacturer wiring diagrams, workshop manual and diagnostic tester we could utilise. I brought only Picoscope set because the workshop did not have any.

Background:
The customer complaint was “Engine warning light ON”
Workshop has carried the usual test according to diagnostic test plan followed by short test drive with no DTC and returned the vehicle back to customer which caused return repair as the same DTC and Engine warning light returned following day, the problem was very intermittent.
The workshop updated all CM to latest versions and then decided to replace the camshaft adjusters on all 4 camshafts. After installed new cam adjusters, the same DTC has logged again on the extensive test drive.
Next step they swapped the camshaft actuators solenoids from another good known car, but the DTC has returned once the engine has warmed up on long test drive. The replaced parts did not fix the problem.

Our diagnostic job started:
The customer complaint verification:
We have replicated customer vehicle usage by test drive in the real traffic and confirmed the engine warning light has switched ON, the ODIS scan showed up the same fault DTC P000B Camshaft Position Slow Response again.

Further functional testing:
The DTC did always log on after engine warmed up to high temperature while test drive, especially on the traffic with harder acceleration and many stops at traffic lights. We have also learned that the DTC can be reproduced even without the test drive by allow the engine warm up by leave it idle until the engine gets very hot, then rev up several times in the workshop.

Basic diagnostic plan:
We could use the Pico-scope and ODIS MVB and we could also compare the results with good known car that was available in the workshop.
The question was where to start with the troubleshooting. We believed the new parts replaced by the workshop were installed correctly, the camshaft timing had to be mechanically correct also, so we take it as not the area to search for the problem. Our most logical direction was to check the electric signals on the camshaft sensors and solenoids, the oil pressure and temperature, cam solenoids current as well as ECU power supply & ground.

Access to component locations:
We could reach the Solenoid valve of the exhaust cam adjuster and monitor the voltage, ground quality and duty cycle with oscilloscope, also the exhaust camshaft hall sensor was easy to monitor. Unfortunately, we couldn’t probe the crank sensor signal due to difficult access to ECU socket where it is the only possible location to back-probe the signal wire. One more disappointment was that we could not measure the bank 1 cylinder head oil pressure because not possible to reach the oil channel, this oil pressure measurement could give us valuable information especially if compared with good known car. We had available the same vehicle model for comparison which was very valuable because there was not any specification in the manufacturer workshop manual or ODIS diagnostic tester.

The data acquisition:
We have connected the ODIS and deleted the fault memory (the DTC was recorded on many previous logs), then ignition cycle and confirmed no DTC present. The engine did not run over night, was cold around 30 degrees.
The idea is to replicate the fault while monitoring the live data of the cam adjustment by ODIS diagnostic tester from start-up cold the engine.
So push the starter button, engine starts, let’s review the following ODIS screenshots. The camshaft is adjusted to -50 degree, the SAI pump is running, the engine is on high idle. (It’s the same as the good known car we are monitoring, the cam angle of the good known car was also -50)
Picture1.jpg
Few moments later the SAI cuts off and idle speed drops to normal idle. Both exhaust cams are on -30 degree. (The same values as the good car)
Picture2.jpg
Basic setting:
One of the important steps to verify the cam phasing functionality is the basic setting procedure so we have decided to carry it out. The precondition is minimum 80 degrees for the coolant and engine oil.
The engine continued idle up to the point when the basic setting of the exhaust camshaft adjusters was possible.
Once the engine reached up the desired temperature, we have carried out the camshaft phasing basic setting as on the pictures below.
Basic Setting.jpg
Conclusion after these steps:
The mechanical adjustment of the cam timing is correct, and the basic setting will pass successfully after the engine temperature (oil and coolant) have reached 80 degrees C. The same process was done on comparison vehicle and both results are identical, not any fault or unusual value was recorded.

Next step, rev up and record:
Test on higher RPM, we have tried to rev up the engine just after the basic setting passed and the value moved up and down exactly like on the compared vehicle. See the pictures below, first to -50 degree and then close to -30 and then -25 degree, very similar as the good known car. All was OK until now, no unusual value or DTC have logged into the engine fault memory
Rev Up.jpg
Finally the Picoscope time:

Now is the time the Picoscope can prove its power by recording the real signals and values directly on the wires or let’s say we can see the same things as the ECU see.

The Good Known car first:
We are comparing the measurement with the good known car which we have measured first. Mainly to practice our Pico setting and learn how the good signal looks like.

The Picoscope connection:
We backpinned the solenoid power supply B1 exhaust (Blue “A” channel). The red "B” Ch. goes to the bank 1 exhaust solenoid signal (This is ground switching PWM by ECU), Green “C” Ch. goes to camshaft hall sensor exhaust B1 signal. Yellow “D” Ch. goes to exhaust solenoid PWM signal wire on the B2 for comparison. Monitoring the PWM together with the adjustment angle on ODIS. Below is the result of the measurement recorded by Picoscope on the good known car. The PWM B1 exhaust cam solenoid is 58% at the temperature over 100 degrees (Red channel “B”).
Picture8.jpg
Next step, add the current clamp:
On the screenshot below is already hot engine after we accelerated few times. This picture captured the current measured on the signal wire of the exhaust solenoid bank 1. Unfortunately, we could not record the current with the good known car due to clamp malfunction caused by excessive heat from the engine, but the current waveform looked identical with the good known car. It is still worth to share here even we cannot compare with the faulty car. (The current is displayed by the channel “D” where was previously connected the B2 exhaust solenoid signal wire PWM voltage)
Picture9.jpg
Finally, the faulty vehicle and the values showing something wrong:
We have left the engine idle for additional 15 minutes and then taken another screenshot of the MVB, the values were still OK. Then we revved up the engine few times more and the oil pressure raised up accordingly, the same as on the good known car. Oil pressure and temperature is recorded from ODIS MVB, actual values.
Now finally something starts happening. After the engine revved up few times again and left on idle, the oil pressure went too low (1.2 bar) and the angle of the B1 exhaust adjuster is dropping to -17 degree as monitored by ODIS. The DTC is not logged yet but it is obvious that the B1 exhaust adjuster is unable to keep the desired angle while the PWM trying to hold up.
Picture10.jpg
The condition lasted only few seconds and then the cam adjustment system failed, oil pressure dropped lower to 1.1 bar at temperature 95 degrees and finally the DTC is logged to the engine ECU fault memory. The exact moment is captured on the waveform below. It looks like the ECU simply cuts off the Bank 1 PWM signal and moment later the Bank 2 also if any camshaft value is out of specification for given time period.
Picture11.jpg
Following pictures displays the ODIS MVB.

The following pictures has been taken in about one second interval before the solenoid stopped working and the DTC logged in.
CamValue.jpg
The last picture no 8 shows when the solenoid stopped working.

Our observation sorted out:
• The engine operates normally at the cold temperature up to little over 80 degrees of the engine oil.
• When the engine starts at the cold condition, the cam angle moves from -50 to -30 -25 and -20. This is normal, without any problem.
• When the oil temperature raises over 90 degrees and close to 100. The B1 Exhaust adjuster fails to hold the desired angle and DTC logs in.
• If the RPM is manually held higher than normal idle, around 1000 rpm, the B1 exhaust adjuster is working fine.
• The good known vehicle oil pressure drops sometimes close to 1.5 bars but the good engine has not any problem with it.
• After several acceleration, stationary car at oil temperature 90 to 100 degrees and then letting the engine idle, then several seconds on idle and the B1 Exhaust adjuster fails to hold the specific angle.
(The oil pressure sensor is fitted on the engine block near the pump but before the oil channels splits to individual cylinder heads. The sensor basically does not measure the oil pressure in the cylinder head. We also cannot reach the sensor and backpin it, the only data we have is from the ODIS actual values)
Conclusion:
The exhaust camshaft adjuster B1 has insufficient oil pressure supplied to the channel causing the out of specification camshaft adjustment.

There can be several reasons for the insufficient oil supply:
1. Faulty adjuster (it has been replaced by new part)
2. Faulty solenoid (solenoids were swapped from another good known vehicle but ending up with the same result. Tested in previous days before our visit) This test was done with the original solenoids the shop installed already back.
3. Insufficient oil pump performance (here we see the pressure over 3 bars at the oil pressure sensor location and at the time when the symptoms already appear. We suggest the oil pump is OK. (The oil pressure sensor is fitted on the engine block near the pump and not at the cylinder head)
4. Internal oil pressure leak between the oil pressure sensor location and camshaft adjuster, for example blown out some “O” ring, loosed oil channel plug or worn out some part on the B1 cylinder head. (Here would help comparison of the oil pressure measured nearby the adjuster at the cylinder head area)
5. Some debris in the oil channel at the cylinder head B1 area. (We did not see any trace of metal chips or particles when adjusters replaced)

Fixed or not fixed the car?
There is still the question. If we could save the vehicle down time, the labour hours and parts that were installed on the engine prior our Picoscope approach?
If the measurements were taken including the oil pressure measured on the cylinder head, this would require some customised adapter, would it help? Probably not and the camshaft adjusters would have been replaced anyway as this would be the most likely part causing oil pressure drop.
But it could get worse, the next part to replace would be most likely the engine ECU, then it would follow by engine wiring harness and possibly many more parts and many more weeks in the workshop.
No, we did not fix the car, final decision of the workshop was to replace complete engine.
The diagnostic technician world is not easy and often very tricky, important is not giving up but keep trying, and this is the main reason I have decided to share this case study.

Here is a picture where the oil pressure can be measured very accurate with the Pico pressure transducer but unfortunately this cannot be reached when the engine is completely assembled and ready to run, no space to fit the pressure probe in this oil channel.
Head.jpg
Thank you for reading.

Steve Smith
Pico Staff Member
Pico Staff Member
Posts: 1581
Joined: Sun Aug 25, 2013 7:22 am

Re: DTC P000B - Camshaft Position Slow Response (Bank 1)

Post by Steve Smith »

Hello and thank you so much for the post above

The time taken to document your process during diagnosis and then to write this process up into human readable format takes forever. This is much appreciated and rest assured you are helping someone somewhere.

Thank you again as this information will help others to consider the hydraulic aspect of VVT control as well as the PCM control and associated components

Take care....Steve

User avatar
Rfmotors1
TwoWaves
TwoWaves
Posts: 86
Joined: Fri Aug 31, 2012 8:14 am

Re: DTC P000B - Camshaft Position Slow Response (Bank 1)

Post by Rfmotors1 »

Thank you Steve,

We are usually writing simple case study at our training courses and our technicians are often sourcing inspiration from Pico Forum.
This camshaft variable timing case we have posted is very long, it went to details. We didn't even come to clear conclusion but this is what often happens in the real world and even partial conclusion may save lots of parts and labour hours.

Regards,
Roman

Steve Smith
Pico Staff Member
Pico Staff Member
Posts: 1581
Joined: Sun Aug 25, 2013 7:22 am

Re: DTC P000B - Camshaft Position Slow Response (Bank 1)

Post by Steve Smith »

Hi Roman, thank you for the feedback and what an interesting point you make regarding diagnosis and "not coming to a clear conclusion".

There are so many cases where to find the absolute offending component is more time consuming and therefore costly than the value of the vehicle itself

This is where having fundamental knowledge (often product knowledge) and great rapport with the customer will deliver a "Win" every time

Your decision to replace the engine was not taken lightly but based on methodical evaluation of components & signals to arrive at such a "measured conclusion". This was the best long term solution for everyone (not just the customer)

I used the paragraph below in a recent NVH study which holds true for all diagnostic tasks

"Tackling complaints of NVH is no different from how we approach any diagnostic challenge. We use a process that will deliver results, which we can apply to make an informed decision on how to proceed to be able to provide a conclusion. Note however, the conclusion may not be a fix but can still be satisfactory to all parties involved!"

This does sound like "we may never find out what is actually wrong with your vehicle" and this may be true but we can rectify the problem. (I hope this makes sense)

If ever you need Case Study material Roman the following link will help https://www.picoauto.com/library/case-studies where all case studies are featured in the monthly Pico Newsletter https://www.picoauto.com/library/newsletter-archive

Thank you again, take care......Steve

Post Reply