Mercedes CLA Forum banner

21 - 40 of 41 Posts

·
Registered
Joined
·
10,805 Posts
The voltage gauge on my obd display is something I watch like a hawk
Now 12.4 is “ok” so as long as the battery recovers to 12.6 after shutdown say after 1 hr
This car does not charge continuously ... the charging circuit has some algorithm which accounts for load etc (eg no charge going uphill to remove alternator parasitics, moderate charge at 14V cuz the battery needs it while cruising, full charge at 15V when going down hill or coming to a stop kinda like regen)
But if 12.4 is typical when static then its dying though in both cases for me battery death was immediately after a short trip no warning and was <10V with trunk pop etc
 

·
Registered
Joined
·
24 Posts
Discussion Starter #23
Ok noted.. the intake manifold pressure sensor error came up again this morning... looks like this is my main issue...
 

·
Registered
Joined
·
10,805 Posts
Thats quite a few under voltage flags
If you dont see any charge activity (monitor the battery section) then the alternator or charge circuit may need help?
Low voltages can cause all sorts of sensor issues so keep that in mind
Until the obd reader arrives just wire a voltmeter to the obd port and see what the numbers are to at least see what the alternator is really doing
Watch out for shorting those inserts are close together
 

·
Registered
Joined
·
24 Posts
Discussion Starter #27
Did monitor using xentry.. volt was around 12+ did not went up to 13 Nor 14.... I just changed my battery last week so I doubt it..
 

·
Registered
Joined
·
24 Posts
Discussion Starter #29
I feel the same way too. What I found out today is that when I come to a stop and the car will off by itself due to the eco function when it try To start up again my screen will go black and came back. My auxiliary battery didn’t push any warning light. And also for the logging what should I log? Intake manifold pressure, fuel rail pressure, voltage and throttle position?
 

·
Registered
Joined
·
10,805 Posts
I feel the same way too. What I found out today is that when I come to a stop and the car will off by itself due to the eco function when it try To start up again my screen will go black and came back. My auxiliary battery didn’t push any warning light. And also for the logging what should I log? Intake manifold pressure, fuel rail pressure, voltage and throttle position?
i log everything! one never knows ...

but sure sounds like a alternator/charge issue ... if the battery is new ... which it wont be anymore if the plates are starting to cloud up with low charging cycles etc etc
 

·
Registered
Joined
·
24 Posts
Discussion Starter #31
Hard to log everything in one.. well maybe this obd sucks.. got one coming in this Thursday... anyway I tried to charge the aux battery yesterday turns out that the aux battery can’t be recharge. I’m having the aux battery malfunction warning now... aux battery will arrive today
 

·
Registered
Joined
·
24 Posts
Discussion Starter #34
Low throttle high intake pressure... while high throttle with Low intake pressure, I have forgotten to log fuel rail pressure but I have added it in now
 

·
Registered
Joined
·
10,805 Posts
Man this wabbit hole is getting deeper ...
Was thinking to at least try to diagnose (long shot anyway) you will need boost iat rpm cattemp throttleactual throttlecommanded fuelrail voltage timing ambient ... then plot them together and hunt for anomalies
If nothing looks “odd” then just have to bow to the dealer or indie mechanic
 

·
Registered
Joined
·
1,086 Posts
Replace voltage regulator on alternator
80+ dollars for part
 
21 - 40 of 41 Posts
Top