Hello! It's been a while since I last visited NICO. In fact, I used to be a moderator here but work-related activities got in the way.

Background: 2006 M35 Sports. Per my daughter, the car stalled on Saturday, 17Jun17 but was able to re-start it without any problem. The “SLIP” indicator was intermittent. The following day, Sunday, 18Jun17, I checked battery voltage, 12.72V; started car and checked alternator voltage, 14.30V. The SES (Service Engine Soon) was ON and I pulled 2 codes – P0340 (CMP SEN/CIRC-B1) and P442 (EVAP, SMALL LEAK). Reset the SES. Checked the M35 FSM and internet and based on diagnostics, decided to order Camshaft Position Sensor (CMP) from Autozone (Duralast SU65156). Received order confirmation from AZ via email. Please note that I normally use OEM parts (Infinitipartsusa.com and the likes) but it will take at least 3 days to get the replacement part. The car must be fixed ASAP since I will be leaving on a business trip on Monday, 19Jun17.
I got the part from AZ by 9:30 AM, Sunday and started with the replacement process. Disconnected the battery and removed engine cover and the vacuum line above the Camshaft Position (CMP) sensor. Removed old CMP sensor and cleaned connectors. The old sensor had traces of oil around it. Applied dielectric grease on connector and oil on the new CMP sensor o-ring. Installed the new CMP sensor, reconnected battery and started the car. Run the car for over 5 minutes at idle, no problem. Shutdown the car and went for lunch @ 11 AM with family, Father’s Day. Came back to start the car @ 7 PM but battery was dead - 4.35V. The battery is 4 years old. There's no light nor accessories on so I decided to hook up the battery charger. Two hours later and the battery charging voltage only at 6.5V.
Since there is a possibility that the new sensor from AZ is bad, I decided to re-install the original sensor. As soon as I installed it, the battery voltage went up to 7.28V. Reconnected the charger and the voltage was at 12.78V immediately. We'll find out tomorrow (will disconnect charger). I asked my daughter not to use the car but try to start it in the afternoon, after work.
Now here is my question - has any one encountered this problem before, battery getting discharged after installing a new Camshaft Position sensor?

Welcome back! Sucks it's on such terms though heh...

That is definitely odd. The battery is a little on the older side...but the fact that voltage went up after putting the OEM one back is strange...I wouldn't think any of those sensors use juice until the key is turned on...

Speaking in general terms in the industry, and I would think (99.99 % sure) our cars use the same engineering protocols as all else, it is very unlikely the sensor is at fault for your battery drain. here is why, in my opinion:

To start with like Ilya stated, key on activates 12v ECM inputs. (yes, there is 12v constant to the ECM, but this does not feed the output drivers for the sensors. Separate 12v ECM ignition on inputs feed outputs for the various sensors that are then driven by 5 volt regulators within the ECM. Sensors work on low voltage only, and draw only milliamps. I have never seen what you describe happen before. I have heard of aftermarket sensors performing incorrectly, but never like the scenario posted.

If your problem was short induced, any component inducing that kind of drain on the battery would be drawing a significant amount of current. That component would most likely be warm (or hotter) then surrounding ambient temps.. In essence, although I cannot see the new sensor as being at fault, if it was causing the problem, the sensor itself & most likely the ECM would be warm as the battery drain was occurring.

I could go on & on, but if it were my car, I would start with a good check of the battery/charging system. As Ilya stated, a 4 yr old battery could be suspect. Starting with a fresh battery and taking it from there is what I would do. Monitor your new battery with a volt meter every now & then as you have already done. Even after long periods at rest, base voltage (car & ignition off) should always read at or above 12.5 volts.

A fast way to check if your alternator could be suspect in battery drain, is to see if the alternator temperature is warmer than the surrounding components while car has been sitting with ignition off. (car must not be running, and must be off long enough for surrounding temps to stabilize, do not start car). If it is warmer, further alternator/regulator checks might be warranted!

Update: Battery was not fully charged as of 5 AM this morning but since I have an early morning flight, I disconnected the charger then measured battery voltage, 13.70V. Started the car and then ran it at idle for over 5 minutes. At 6 PM today, my wife started the car and let it run at idle for 30 minutes to charge the battery. My daughter will use the car tomorrow. Hoping for the best.

I still don't know why the battery got discharged. Never happened before since the battery was replaced 4 years ago. It could be a coincidence or something else. Before replacing the sensor, I checked the harness to the alternator, looks good and the connections are tight. Per FSM, the sensor receives battery voltage with ECM relay energized (Ign. ON) via Pin 3, Pin 2 for the Phase sense and Pin 1 to ground. So Ilya is right about the sensor getting powered only with engine running.
I will do more checks once I get back home on Saturday.

Thanks, everyone. Will give an update once root cause is identified.

It could be simply the battery, I did warranty on them for years and have seen some really weird stuff........................and some of what you post. You can easily have shorts that come and go based on loading the battery. I've had volts go back up as the short cools then the battery plate warps to not be shorted again, it reshorts as soon as you load it hard enough again. 4 years old says change it anyway. I found that most batteries regardless of the warranty, 2, 3, 7 year tend to die around 3-5 years. A few will make the warranty numbers but not many if the really high year counts. On the flipside, I had one 3 year battery go ELEVEN years personally, a definite fluke there. If the battery is in a car that sits a bunch, then even more likely that 2-3 years will by odds be about the normal life. Long sits kill life like you would not believe if not constantly trickled. I saw scads of longlife batteries ruined by people with rare collector cars that they let sit to drive maybe once a month.

Yes, 3 wire sensor means a Hall effect type and only powered with key on engine running. And like pretty much said above Hall sensors don't accept a lot of power like a rundown short, they are delicate and don't make much sensor signal and burn out easy if overamped. They don't use a big power switching transistor, just a weak little power sensing one. A battery short should ruin one in pretty much a few seconds.

FYI, after testing hundreds of cars of all brands I came to realize that 12.2 volt is about the point at which many start to have issues of some type. I call 12.3 barely good on most of them. New being of course around 12.8 and good being 12.5 and up. Some few cars can work as low as 11.9 but that was definitely the few oddball ones. Most are showing computer sensor fake responses that low.

I would change the battery first.

There is an easy way to test this. Look up on Youtube, Eric the Car Guy, how to perform a parasitic draw test. Once you get your meter hooked up like he says, just pull the plug for that sensor instead of pulling fuses like he talks about. Watch the video and you'll be able to figure it out.

There is an easy way to test this. Look up on Youtube, Eric the Car Guy, how to perform a parasitic draw test. Once you get your meter hooked up like he says, just pull the plug for that sensor instead of pulling fuses like he talks about. Watch the video and you'll be able to figure it out.

It's been a while since the original posting and I just realized I didn't give the final update. Yes, the problem was with the sensor purchased from AutoZone, returned. I bought another one from Winchester Auto and the problem went away. No more fault code nor stalling and the battery working normally.

loystock wrote: ↑

Tue Dec 07, 2021 9:34 am

It's been a while since the original posting and I just realized I didn't give the final update. Yes, the problem was with the sensor purchased from AutoZone, returned. I bought another one from Winchester Auto and the problem went away. No more fault code nor stalling and the battery working normally.

This is why I love the forums.
Thanks for the update, glad to see you here.