ECM, electrical issues...gremlins?

[Valkyrie14]

Just looked up BCM. This could be a development. I removed it when I fixed the heater blend door. Could be a loose harness or plug.

[Axe55]

Good luck man, chasing electrical issues is a major PITA, hope it's just a loose connection on the BCM!

[Valkyrie14]

A new BCM requires dealer programming?

[Valkyrie14]

Originally Posted by Axe55

Good luck man, chasing electrical issues is a major PITA, hope it's just a loose connection on the BCM!

Thanks, chasing electrical is literally the worst in my book. I may just take it to a specialist and hand over the check book if it comes to that.

[Valkyrie14]

Originally Posted by AlanRubin

The ECM does not control the lighting, that's the body control module.

I mean, that can cause a misfire on#4, but won't effect the lighting of the car.

I got under there and pressed on all of the harnesses and wiggled the wires. I heard a click, which was either a harness fully going in or my neck. But since then all lighting is working properly.

The battery is still showing 14-15V but that is apparently an unrelated issue.

[gtstorey]

Do you have access to another vehicle so you can confirm your multi-meter voltage reading? I've done a little online research on this and can't find any mention of a normal car battery being able to charge to above 13 volts.

[Valkyrie14]

Originally Posted by gtstorey

Do you have access to another vehicle so you can confirm your multi-meter voltage reading? I've done a little online research on this and can't find any mention of a normal car battery being able to charge to above 13 volts.

I could check the wife’s battery easily enough. The dash cluster is telling 14-15V. I saw on some threads that our cars normal operating range includes 15V, but I couldn’t find that in the owners manual anywhere. My multimeter read in the 15s so I figured it wasn’t off, because that would mean the cars voltage sensor is exactly as off as my multimeter. What are the odds of that.

[gtstorey]

I'm saying to check the no load/non-running voltage. Switch off, direct to battery terminals to see if you are really getting 15v from the battery. I'm far from an expert, but 15v from a battery contradicts everything I have ever heard for a car battery. If it is 15v then I still think you had better replace the battery.

[AlanRubin]

Your range, 14V to 15V is fine. If I let my car sit for more than a week, it will run at
15V for a long while. It will drop as I drive. When it's above 50 degrees, and it's run a
while, it will drop to 13.5V. If it's in the 30s, it will run at 15V for a while. I did not
work yesterday, and it got cold. I more than expect it to run at 15V today, for
at least the first 160 miles of the trip. As soon as I reach Aurora, and turn it
off, restart will probably be in the 14V range.

These cars have 6-charging modes, based on battery temperature, and
current use sensing. 15V is one of the charge modes, you can find this
information in the service manual.

[AlanRubin]

Engine running, accessories OFF, measure and record the battery voltage at the C1 battery terminals. The
voltage should be between 12.6 and 15.0 V.

Observe the appropriate module scan tool Battery Voltage parameters. Verify that the scan tool displays a
value that is within 2 V of the C1 battery terminal voltage.

DTCs:
B1517 07
The battery voltage is greater than 16 V.
The engine speed is greater than 1,100 RPM.
The above conditions are met for 15 seconds.

B1517 5A
The battery voltage differs by 2 V on the BCM battery sense circuits for 10 seconds.

There are 6 modes of operation and they include:
Battery Sulfation Mode
Charge Mode
Fuel Economy Mode
Headlamp Mode
Start Up Mode
Voltage Reduction Mode

Commanded Duty Cycle & Generator Output Voltage:
10% 11 V
20% 11.56 V
30% 12.12 V
40% 12.68 V
50% 13.25 V
60% 13.81 V
70% 14.37 V
80% 14.94 V
90% 15.5 V

Battery Sulfation Mode
The BCM will enter this mode when the interpreted generator output voltage is less than 13.2 V for 45 minutes.
When this condition exists the BCM will enter Charge Mode for 2-3 minutes. The BCM will then determine
which mode to enter depending on voltage requirements.

Charge Mode
The BCM will enter Charge Mode when ever one of the following conditions are met.
The wipers are ON for than 3 seconds.
GMLAN (Climate Control Voltage Boost Mode Request) is true, as sensed by the HVAC control head.
High speed cooling fan, rear defogger and HVAC high speed blower operation can cause the BCM to
enter the Charge Mode.
The estimated battery temperature is less than 0°C (32°F).
Battery State of Charge is less than 80 percent.
Vehicle speed is greater than 145 km/h (90 mph)
Current sensor fault exists.
System voltage was determined to be below 12.56 V

When any one of these conditions is met, the system will set targeted generator output voltage to a charging
voltage between 13.9-15.5 V, depending on the battery state of charge and estimated battery temperature.

Fuel Economy Mode
The BCM will enter Fuel Economy Mode when the estimated battery temperature is at least 0°C (32°F) but less
than or equal to 80°C (176°F), the calculated battery current is less than 15 amperes and greater than -8
amperes, and the battery state-of-charge is greater than or equal to 80 percent. Its targeted generator output
voltage is the open circuit voltage of the battery and can be between 12.5-13.1 V. The BCM will exit this mode
and enter Charge Mode when any of the conditions described above are present.

Headlamp Mode
The BCM will enter Headlamp Mode when ever the headlamps are ON (high or low beams). Voltage will be
regulated between 13.9-14.5 V.

Start Up Mode
When the engine is started the BCM sets a targeted generator output voltage of 14.5 V for 30 seconds

Voltage Reduction Mode
The BCM will enter Voltage Reduction Mode when the calculated ambient air temperature is above 0°C (32°F).
The calculated battery current is less than 1 ampere and greater than -7 amperes, and the generator field duty
cycle is less than 99 percent. Its targeted generator output voltage is 12.9 V. The BCM will exit this mode once
the criteria are met for Charge Mode.

Charge Indicator Operation
The instrument panel cluster illuminates the charge indicator and displays a warning message in the driver
information center if equipped, when the one or more of the following occurs:
The engine control module (ECM) detects that the generator output is less than 11 V or greater than 16 V.
The instrument panel cluster receives a GMLAN message from the ECM requesting illumination.
The instrument panel cluster determines that the system voltage is less than 11 V or greater than 16 V for
more than 30 seconds. The instrument panel cluster receives a GMLAN message from the body control
module (BCM) indicating there is a system voltage range concern.
The instrument panel cluster performs the displays test at the start of each ignition cycle. The indicator
illuminates for approximately 3 seconds.

[gtstorey]

Originally Posted by AlanRubin

Your range, 14V to 15V is fine. If I let my car sit for more than a week, it will run at
15V for a long while. It will drop as I drive. When it's above 50 degrees, and it's run a
while, it will drop to 13.5V. If it's in the 30s, it will run at 15V for a while. I did not
work yesterday, and it got cold. I more than expect it to run at 15V today, for
at least the first 160 miles of the trip. As soon as I reach Aurora, and turn it
off, restart will probably be in the 14V range.

These cars have 6-charging modes, based on battery temperature, and
current use sensing. 15V is one of the charge modes, you can find this
information in the service manual.

He has had 15v when the car isn't running..

[AlanRubin]

Originally Posted by gtstorey

He has had 15v when the car isn't running..

I think he needs a new meter. I have never seen a 12V battery put out more
then 13.3V when out of the car, let alone in the car, connected.

I have an LED volt meter in mine, and when I turn the car off, it starts
dropping from 13.8, and down. Settles at around 12.6 to 12.8, or 12.4
colder out, or sat for a while.

The meter is on all the time, so I can see the voltage as soon as I open
the door.

They can hold 15 volts at max, but it doesn’t mean the voltage will remain constant.

[Valkyrie14]

This is awesome, and I have learned a lot about our cars battery system. Glad I posted.

I will check the wife’s battery same time I check mine. For what it is worth I did replace the battery last week just to be sure.

After reading all of this I am comfortable with the V being up to 15 while driving. It is colder here, but it is my DD.