[chrishe]

For the last two months or so, every time I start the car I get a "Forward Collision System Reduced" message. It quickly goes away, but at the same time I started getting three or four beeps nearly every time I slow down and stop, whether or not there are any cars in front of me.
I've taken the car to the dealer twice now and they seem powerless to do anything about it. The only thing they did was to replace a wiring harness but it didn't solve the problem. They more or less told me it didn't seem to be affecting driveabilty of the car, so not to worry about it.
I can't find anything about this message in the manual. I've seen a few posts about various Forward Collision System error messages on this board, but none of them that particular message. I've tried all the ideas I've seen - cleaning the sensors, cycling the collision system distance, even switching off the collision system audible warning all to no avail.
Strangely the collision warning itself with the flashing red lights does still appear to work, but I don't like to test it too much as it means approaching the car in front at an unsafe speed.

 

[jcanoe]

For the last two months or so, every time I start the car I get a "Forward Collision System Reduced" message. It quickly goes away, but at the same time I started getting three or four beeps nearly every time I slow down and stop, whether or not there are any cars in front of me.
I've taken the car to the dealer twice now and they seem powerless to do anything about it. The only thing they did was to replace a wiring harness but it didn't solve the problem. They more or less told me it didn't seem to be affecting driveabilty of the car, so not to worry about it.
I can't find anything about this message in the manual. I've seen a few posts about various Forward Collision System error messages on this board, but none of them that particular message. I've tried all the ideas I've seen - cleaning the sensors, cycling the collision system distance, even switching off the collision system audible warning all to no avail.
Strangely the collision warning itself with the flashing red lights does still appear to work, but I don't like to test it too much as it means approaching the car in front at an unsafe speed.

How old is the Volt? It could be a loose 12V AGM battery terminal connection or a failing 12V AGM battery. A bad 12V battery can cause all sorts of sensor issues.

 

[Steverino]

How old is the Volt? It could be a loose 12V AGM battery terminal connection or a failing 12V AGM battery. A bad 12V battery can cause all sorts of sensor issues.

It can't be more than 2 years old based on the forum this was posted in.

 

[chrishe]

It's a 2017 Gen 2 Premier.

 

[jcanoe]

It's a 2017 Gen 2 Premier.

It's easy to get to the battery underneath the flooring of the hatch area. Check the voltage of the 12V AGM battery (when the Volt is not powered on) and also that the battery terminal connections are tight. If the at rest battery voltage is 12.3V or higher then the battery is probably fine, less than 12.0V and there is definitely a problem with the 12V battery.

 

[hellsop]

It's easy to get to the battery underneath the flooring of the hatch area. Check the voltage of the 12V AGM battery (when the Volt is not powered on) and also that the battery terminal connections are tight. If the at rest battery voltage is 12.3V or higher then the battery is probably fine, less than 12.0V and there is definitely a problem with the 12V battery.

I still contend that's too low for a resting AGM. And every manufacturer I've checked agrees: "good" is about 12.8, 12.2 is "half dead" http://www.duracell-automotive.com/fileadmin/content/docs/Duracell-techn-ratgeber-gb.pdf (p 15)

 

[jcanoe]

I still contend that's too low for a resting AGM. And every manufacturer I've checked agrees: "good" is about 12.8, 12.2 is "half dead" http://www.duracell-automotive.com/fileadmin/content/docs/Duracell-techn-ratgeber-gb.pdf (p 15)

The Duracell documentation refers to open circuit voltage. My voltage readings are with the Volt powered down but still powering the infotainment screen, interior lighting and audio system. I can add more load to the circuit by turning on the headlights and high beams and watch the voltage begin to drop even more but I am content to see an initial reading of 12.9 V then dropping to 12.3V and holding steady at 12.3V on the plug-in USB charger with voltmeter. I have never tested this device for accuracy. My sense of "Danger Will Robinson!" would only kick in if and when I see the AGM battery voltage drop to 12.0V.

 

[fishhawk]

OP, check your vehicle settings. See this article:http://sandyblogs.com/techlink/?p=8330
There are three possible settings for the Forward Automatic Braking system:

Off
Alert
Alert and Brake

The Forward Collision System Reduced DIC message will be displayed when the Forward Automatic Braking system has been set to the “Alert” setting in the Vehicle Settings on the infotainment system.

 

[chrishe]

The Duracell documentation refers to open circuit voltage. My voltage readings are with the Volt powered down but still powering the infotainment screen, interior lighting and audio system. I can add more load to the circuit by turning on the headlights and high beams and watch the voltage begin to drop even more but I am content to see an initial reading of 12.9 V then dropping to 12.3V and holding steady at 12.3V on the plug-in USB charger with voltmeter. I have never tested this device for accuracy. My sense of "Danger Will Robinson!" would only kick in if and when I see the AGM battery voltage drop to 12.0V.

Thanks for all your help. I checked my battery, the terminals are tight and I measured the following voltages with the car fully charged:

Still plugged in to Level 2 charger 13.73v
Unplugged 12.82v
Drivers door open and DIC lit up 12.57v
Powered on and with headlights on 14.65v
Powered off with drivers door closed 12.56v
Plugged back in to charger 12.61v

It looks as if the battery is probably OK, but some of these readings don't make much sense to me. Why, for instance, does the voltage increase to 14.65v when the headlights go on?

Thanks again

 

[scottf200]

Thanks for all your help. I checked my battery, the terminals are tight and I measured the following voltages with the car fully charged:

Still plugged in to Level 2 charger 13.73v
Unplugged 12.82v
Drivers door open and DIC lit up 12.57v
Powered on and with headlights on 14.65v
Powered off with drivers door closed 12.56v
Plugged back in to charger 12.61v

It looks as if the battery is probably OK, but some of these readings don't make much sense to me. Why, for instance, does the voltage increase to 14.65v when the headlights go on?

Thanks again

Guessing turning on the headlights with the power on triggered the APM (think alternater on ICE car) to kick on.

"APM is rated at 165amps at 12 Volts (probably 14.4v) and a max wattage of 2200watts."

Gen 1 Volt APM doc: http://media3.ev-tv.me/VoltAPMUserGuide.pdf
via: https://gm-volt.com/forum/showthread.php?242946-APM-14V-DC-DC-converter-replacement

 

[jcanoe]

Thanks for all your help. I checked my battery, the terminals are tight and I measured the following voltages with the car fully charged:

Still plugged in to Level 2 charger 13.73v
Unplugged 12.82v
Drivers door open and DIC lit up 12.57v
Powered on and with headlights on 14.65v
Powered off with drivers door closed 12.56v
Plugged back in to charger 12.61v

It looks as if the battery is probably OK, but some of these readings don't make much sense to me. Why, for instance, does the voltage increase to 14.65v when the headlights go on?

Thanks again

When the Volt is powered on the Accessory Power Module (APM) is providing 12V power to maintain the AGM battery and power all of the 12V accessories, The output of the APM varies according to load and temperature and the state of charge of the AGM battery. I have observed voltages with the Volt powered on from 12.4V all the way up to 15.4V (in cold weather.)

 

[brett_cgb]

Thanks for all your help. I checked my battery, the terminals are tight and I measured the following voltages with the car fully charged:

Still plugged in to Level 2 charger 13.73v
Unplugged 12.82v
Drivers door open and DIC lit up 12.57v
Powered on and with headlights on 14.65v
Powered off with drivers door closed 12.56v
Plugged back in to charger 12.61v

It looks as if the battery is probably OK, but some of these readings don't make much sense to me. Why, for instance, does the voltage increase to 14.65v when the headlights go on?

Thanks again

I read somewhere that AGM (Acid Glass Mat) batteries take a slightly higher charging voltage compared to FLA (Flooded Lead Acid) batteries. At start-up, the Volt raises the 12V bus voltage slightly for a few minutes to charge the AGM battery quickly, then lowers the voltage.

I've also heard there is a current sense resistor between the battery neg and chassis for monitoring battery current (for estimating the battery state of charge). This may account for slightly higher voltage from Batt Pos to chassis, or a small voltage between Batt Neg and Chassis.

 

[chrishe]

OP, check your vehicle settings. See this article:http://sandyblogs.com/techlink/?p=8330
There are three possible settings for the Forward Automatic Braking system:

Off
Alert
Alert and Brake

The Forward Collision System Reduced DIC message will be displayed when the Forward Automatic Braking system has been set to the “Alert” setting in the Vehicle Settings on the infotainment system.

Many thanks fishhawk. As you said, putting the system on "Alert and Brake" removed the "Forward Collision System Reduced" message. Seems rather obvious in retrospect, but my dealer didn't know anything about it and there's nothing that I've found in my instruction book about it either.

Anyway, now I know there's nothing wrong with the system, I shall happily go back to just the Alert. I don't want the car taking control and braking; after all I might want to steer or even accelerate to avoid a collision.

Thanks again.

 

[hellsop]

or even accelerate to avoid a collision.

It IS a forward-detecting system...

 

[Blastphemy]

OP, check your vehicle settings. See this article:http://sandyblogs.com/techlink/?p=8330
There are three possible settings for the Forward Automatic Braking system:

Off
Alert
Alert and Brake

The Forward Collision System Reduced DIC message will be displayed when the Forward Automatic Braking system has been set to the “Alert” setting in the Vehicle Settings on the infotainment system.

You just saved me a trip to the dealership, fishhawk. My brand new 2019 Volt Premier was displaying the same warning at startup and I was at a complete loss as to why. Thank you for posting this information! (Mine was set to 'Alert' only, just like chrishe and for the same reason.)