2001 V70 2.4T Brake Failure Service Urgent / Power Fluctuations / Engine Shuddering

[prwood]

I had a chance to pull codes today as well as do some controlled testing.

My OBD reader app pulled codes P1358 (cylinder 2 open circuit) and P0455 (evap large leak). The P0455 has been present ever since I've had the car. The P1358 comes up intermittently because I need to replace my engine wiring harness and several of the ignition coil connectors aren't in great shape.

VIDA/DiCE didn't pull any codes I hadn't seen before. The only CEM code was CEM-8F43 for "Relay, rear washer motor Signal too low" which has been present ever since I've had the car (the rear wiper doesn't work). There was also the ECM-8410 as previously mentioned for Power supply (5-volt) - Signal too low. These new symptoms with the engine clunking and the power fluctuations don't seem to be registering any new codes that VIDA would pick up on. I did make sure to do a full re-read of all modules in VIDA via DiCE.

The controlled testing was more illuminating. I had the HVAC system in the car shut off so that no extra heat was added to the cabin. I drove laps around the neighborhood for a while, for maybe 25 minutes, with no issues. Basically I was just driving straight and turning every so often in a loop. After this period, however, I started to experience the clunking and power fluctuation issues. Specifically, the issues occurred either during or just after I made a turn, in either direction. Once it happened, I started filming the dashboard so that I could get a record of the sounds as well as the indicators on the dash.

You can see a sample of that recording here: https://photos.app.goo.gl/t3ZidNSWwKC5qUDZ6
Note the following about the clip:
- Immediately at the start of the clip you can hear one of the clunks. You can also see that the shift indicator switches from D to 4, and the airbag indicator comes on in the diagnostic cluster. Things go back to normal after a while on the straightaway.
- At about 0:48, just after a turn, you can hear some clunks and you can also see the shift indicator rapidly switching between D and 4, and the airbag indicator comes back on. At 1:03, you can hear the blower motor come on full blast, even though I have the HVAC completely turned off. At 1:14 it shuts off just as I'm about to turn.
- At 1:15 there is a bunch more clunking, gearshift indicator switching from D to 4 and back, and airbag light coming on.
- The last set of clunks comes around 1:57 when I do a turn. After this I head to the roadside and park.

What I gleaned from this is that the issue starts only once a cumulative drive time has been reached (25 minutes or so), and then is only triggered during/after turns. The fact that it only starts after a period of time does seem to suggest a heat-related issue. Although HVAC was turned off, it could just be an issue of temperature of the surrounding circuits as they reach normal operating temperature. I'm not sure what to make of the fact that it is triggered by going around turns. Maybe it's the aforementioned ABS wheel speed sensors being misread by the CEM when they report different speeds during a turn, and triggering the transmission to do weird things?

I suppose my next step should be to remove, inspect, and clean the CEM? Any other suggestions?

[prwood]

If you take the car out again, try running in manual geartronic mode. Someone correct me if I'm wrong, but if this solves the clunking that would probably insinuate a miscommunication in the car's brain, further insinuating previous hypothesis.

Unfortunately my model doesn't have a manual geartronic mode. I think the best I could do would be to switch it into L on the gearshift which I think limits it to only 1st and 2nd gears.

[br0dy519]

I used this when my DIM failed, and also used to try and diagnose whether I was having a CEM issue :

https://xemodex.ca/ca/pdf/DIM%20CEM%20L ... eMODeX.pdf

To me, you want to really just do the "CEM Heat Stress Test" portion, for giggles of course.

[jonesg]

I had a chance to pull codes today as well as do some controlled testing.

My

You can see a sample of that recording here: https://photos.app.goo.gl/t3ZidNSWwKC5qUDZ6
Note the following about the clip:
- Immediately at the start of the clip you can hear one of the clunks. You can also see that the shift indicator switches from D to 4, and the airbag indicator comes on in the diagnostic cluster. Things go back to normal after a while on the straightaway.
- At about 0:48, just after a turn, you can hear some clunks and you can also see the shift indicator rapidly switching between D and 4, and the airbag indicator comes back on. At 1:03, you can hear the blower motor come on full blast, even though I have the HVAC completely turned off. At 1:14 it shuts off just as I'm about to turn.
- At 1:15 there is a bunch more clunking, gearshift indicator switching from D to 4 and back, and airbag light coming on.
- The last set of clunks comes around 1:57 when I do a turn. After this I head to the roadside and park.

What I gleaned from this is that the issue starts only once a cumulative drive time has been reached (25 minutes or so), and then is only triggered during/after turns. The fact that it only starts after a period of time does seem to suggest a heat-related issue. Although HVAC was turned off, it could just be an issue of temperature of the surrounding circuits as they reach normal operating temperature. I'm not sure what to make of the fact that it is triggered by going around turns. Maybe it's the aforementioned ABS wheel speed sensors being misread by the CEM when they report different speeds during a turn, and triggering the transmission to do weird things?

I suppose my next step should be to remove, inspect, and clean the CEM? Any other suggestions?

Wow that's violent. Slamming gears.
Temperature related, it could be the ECM too, it will go nuts if it overheats.
Just a quick simple check, look at the fuse for the ECM cooling fan. It's in the engine bay, can't remember the number but it's in the manual.
There's no passive airflow for the computer if the cooling fan fails and they get as hot as a frying pan even in winter.

You can put a meter on the abs sensor and spin the wheel to test it. AC volts.

[prwood]

Put in some work today, here are the updates:

- I removed and inspected the CEM. I didn't recognize any obvious issues (corrosion, debris, moisture, etc). Looking at the sticker on it, if the manufacture date labeling is similar to other components, it looks like it may have been built in 2007, so this must have been replaced at some point prior to my ownership. I've included some photos below:

- Cleaned the conectors with QD electric connector cleaner. Honestly they looked immaculate, but I did it anyway since everything was apart. Reinstalled everything.
- Ran the 'heat stress test' recommended by xemodex. Did two reps of 5 minutes each with a hair dryer on max. No issues with the DIM or any controls either time (but then again, I never had any issues while parked/idling).
- Shut off the car and took a break for 20 minutes.
- Did a driving test while logging OBD data. No issues while driving for the first 20 minutes. Found that the issue started again after almost exactly 20 minutes of driving (not sure whether to also count the ~10 minutes of idling that I had done before the break). Again the issue was fluctuating power in the cabin (dashboard and control panel lights, blower motors), as well as clunking from the engine/transmission, with ABS and Brake lights lighting up as well as intermittent SRS light.
- I monitored OBD2 Volts on my OBD reader app and noticed that starting when the the OBD volts shot up from their average of around 12.7 to almost ~20 volts:

OBD Voltage.png (43.71 KiB) Viewed 1692 times

- During the periods where the OBD voltage read close to 20v, the dashboard lights were also extremely bright, then went back to normal as the voltage went down and the problem subsided.
- As before, the problem occurred just after performing a turn, and usually lasted for a minute or so while going down the straightaway after the turn. The problem did not occur when idling.
- I also checked the ECM/TCM as well as their enclosure, and did not find any moisture or other visible issues. They were securely attached. My model does not have a cooling fan for this box as far as I'm aware.

Based on the voltage spiking behavior above, and the fact that the CEM seems to be relatively new and in good shape, and didn't respond to a heat test, and the fact that I had that ECM voltage code last summer (which was thought to be due to a failing voltage regulator) I'm wondering if this is a further manifestation of a degrading voltage regulator and/or alternator issue.

[br0dy519]

Nice troubleshooting wood!

If it were me I’d replace the entire alternator at this point (go Bosch only regulator if sourcing one at rebuilder). I just replaced mine this year and had to do the job three times because the rebuilder kept using a chinese aftermarket regulator. Or rebuild yourself with a new pulley and put a new Bosch reg on it.

Can 20V voltage spikes damage components? Need someone intelligent like RickHaleParker to chime in on that.

[abscate]

Oh yes. Get a oscope on the alternator output and check the AC ripple on the b+ Supply.

Nice troubleshooting!!

[prwood]

Oh yes. Get a oscope on the alternator output and check the AC ripple on the b+ Supply.

Nice troubleshooting!!

Unfortunately I don’t have an oscilloscope. Not in the budget to buy one. If I could get a hold of one, what would I be looking for? Do I need to measure directly off of the alternator or can I use the red cable at the fuse box (is that what you mean by b+ supply?)?

I think it’s interesting that the issue happens A) only after 20+ minutes of driving B) only when driving; not when idling. So it must be a combination of something reaching a certain level of usage and then being unable to cope with the load of driving (increased rpm’s?).

[abscate]

Connect with firefox in New Hampshire, I bet his maker space has an oscilloscope that will let you check the AC component of the alternator output.

AC ripple will kill your CANBUS communications, and WREAK HAVOC on other stuff

[prwood]

At this point I may just go with my gut and assume it's the alternator, based on the symptoms. Now just to decide when I'm going to do it and which of the many methods I'm going to use to get the alternator out.