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Discussion Starter #1 (Edited)
Other threads have addressed the maintenance mode where opening the hood turns on the ICE. Hopefully this one done with a DD will answer some of the unanswered questions.

For a 2012 Volt serial 3xxx.

1. It is possible to drive the car in this switch open mode with seemingly normal acceleration FOR A WHILE.
2. The ICE will generate 4-15kW observed and battery Voltage rises showing the battery is charging.
3. The cabin heater transitions to ICE coolant heating.

In my case I opened the hood switch while the car was fully charged and being driven at 30 mph. The car transitioned to apparent CS mode with the A motor putting out about 5 kW at about 1500 rpm and higher when loaded. The driving display ranted about an open hood. The DD readings were consistent with normal CS operation and the console power flow display the same. The joy lasted for about 8 miles when I stopped and turned the car off and then back on again. From that point:

The ICE mode would not stay on when the car was moving faster than a creep. (no pedal). When I tried to accelerate the car it transitioned back to EV mode and drove normally without the ICE. I cycled through three stops and this behavior continued.

Net, the software prevented my using the switch as a hold mode beyond the initial 8 miles. It does look like the hood switch will charge the battery and heat the cabin if open and the car is stationary. The charge rate is on the order of 5kW so its a little above the wall plug's 3.3kw.
 

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Very interesting info, jfkirk!

How do you reset the software status to go another 8 miles?
a) shut close the hood/bonnet so the switch gives an hood closed signal?
would that also need to shut off the Volt then back ON ?

What RPM do you observe when moving with the Volt ? would the ICE engine typically follow
the accelerator pedal?

Thanks!

Francois
B2653
 

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Discussion Starter #3 (Edited)
Very interesting info, jfkirk!

How do you reset the software status to go another 8 miles?
a) shut close the hood/bonnet so the switch gives an hood closed signal?
would that also need to shut off the Volt then back ON ?

What RPM do you observe when moving with the Volt ? would the ICE engine typically follow
the accelerator pedal?

Thanks!

Francois
B2653
I don't know on the re-set. I'll get back on that. Just stopping for a minute and closing the hood did not re-set.
During the initial 8 miles the car car performed as if in CS mode...normally RPM varying with load (1400-2000 rpm), but not reduced power mode where the car is only being propelled by the ICE and the ICE speed is pedal dependent.
 

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So you're saying you got two completely different behaviors from the car - when you pulled the hood while driving, you ended up in a quasi Hold mode (did the engine turn off at low speeds or when decelerating like it will in Hold or other CS modes?) - but when you started the car with the hood open you got a mode like none we've seen before (anti-CS - the engine is on at the opposite times from normal CS,) - engine on at low speeds, but off at higher speeds?

Vewwy Interesting. Aside from the questions above and repeating the test to confirm it's the same, the other thing to try is what happens if you pop the hood while the car is on, but stopped - do you get the quasi Hold, the anti-CS, or something yet different?
 

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I tried this on Saturday by accident. It had occurred to me that I had my Volt for over 2 months and had never opened the hood- so I popped it and the engine turned on, and thought "oh hey- I heard about this". I didn't record my observations as well as the OP but I did push the pedal and drove a little with it popped. I concluded the car drove in "anti-CS" like saghost called it. Engine on when stopped, RPM mapped to accelerator for a short while, and then switched to a mode where the engine was off while underway. I think it's triggered by time more than distance because I didn't drive very far with the hood popped.
 

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jfkirk,

Thank you very much for reporting the results of this experiment. I had been tempted to try it but w/o a scanner would not have known what was happening behind the curtain.

I can think of two possible causes for the change of behavior at 8 miles:

Is it possible that the vehicle thought it had been remote started and allowed running in 'hold' for 10 minutes?

Is it possible that the vehicle thought that it was in EMM and ran in 'hold' only long enough to satisfy the EMM requirement?

Again, thank you for reporting your results.

KNS
 

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jfkirk, thanks for the post. Just to clarify, at 8 miles, you voluntarily shut the car off then turned it back on right? So the change in behavior is likely due to this, not the distance driven? IOW, it had nothing to do with the fact you happened to drive 8 miles, just that you power cycled the car at that point, correct?

You mentioned that the battery was fully charged when you popped the hood to start the experiment. And we know the ICE charges the battery very quickly, similar to a DC fast charge. So I wonder then what was the SOC after you drove 8 miles? One hypothesis could be that you charged the battery to it's max limit, thus triggering the behavior you observed. I would think the SOC would somehow be a factor in how the car responds.

Anyway, if you get a chance to get some more data I look forward to it!
 

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Discussion Starter #8 (Edited)
To the above. Yes the stopping at 8 miles was my choice... The car was still running in ICE mode when I stopped. As to SOC, I did not have it up, but the HV V was around 385 volts....close to the max I have seen. Its possible I hit a limit. However, in the subsequent tries, it was in EV mode between attempts and bringing HV V down did not re-set the SC behavior.

Saghost. I began with the car moving and got CS behavior. Subsequently, I got the "anti-cs" behavior even when I pulled the switch again while the car was moving. My guess is the behavior change was triggered by time or possible a tripped SOC limit? No MIL, so I did not check for a code.

My takeaway is I still do not know enough to hack a hold mode. More tinkering is called for thanks to the thoughtful questions.
 

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Back to trying to find a manual hold mode for MY2012 owners. In my old gas car (BMW). My outside air temperature sensor fell off. Let's not get into why. With the sensor off, the car read the outside default temperature to be -40 Celsius. What if we were to open the circuit in the Volt, would ERDTT kick in and turn the engine on? Just an idea.
 

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Back to trying to find a manual hold mode for MY2012 owners. In my old gas car (BMW). My outside air temperature sensor fell off. Let's not get into why. With the sensor off, the car read the outside default temperature to be -40 Celsius. What if we were to open the circuit in the Volt, would ERDTT kick in and turn the engine on? Just an idea.
This is correct. With B9 removed creating an open circuit = max resistance as detected by the Hybrid/EV powertrain control module 2 K114A will display the max negative temp of -40F/C onto the center touchscreen display and ERDTT will engage immediately...
 

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So who's going to try it first? I don't have a need for hold mode. I'm just helping out those who are looking for manual hold.

This is correct. With B9 removed creating an open circuit = max resistance as detected by the Hybrid/EV powertrain control module 2 K114A will display the max negative temp of -40F/C onto the center touchscreen display and ERDTT will engage immediately...
 

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This is correct. With B9 removed creating an open circuit = max resistance as detected by the Hybrid/EV powertrain control module 2 K114A will display the max negative temp of -40F/C onto the center touchscreen display and ERDTT will engage immediately...
I suspect that once the fluid in the TMS loop heats up sufficiently the ICE will turn off.

KNS
 

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I really hope there is an aftermarket solution for the HOLD mode for us 2012 folks.
GM is on record stating that it's not just a software change inspron, but also a hardware change. Regrettably, I suspect we won't see your hope fulfilled.
 

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1.What about using a combination of hood switch/ OAT disconnection to keep CS mode after the coolant has warmed up?
Open the OAT circuit, then when coolant temp is close to the cutoff point, ground the hood pin wire...

2. How about OAT disconnection AND faking the engine coolant temperature to a couple of degrees before the shutoff point?
From what I found, the engine has a normal mechanical thermostatic valve, so it would not overheat....

Does anyone know if this engine's thermostat is electronically controlled? If so, we could

Even if this gives us a limited amount of hold, it would be better than nothing, and better than MM.
 
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