[krobinso]

Could someone tell me why there are two ground cables? They're called "Transmission Ground" and "Engine Ground" or "sub ground."

I encountered an odd problem last night. The initial symptoms were that the car stalled as I was going around a corner, then seemed to require more gas than it should have to travel on flat ground, and assist was even kicking in on flat ground. The sound of the engine turning over was muted each time I turned the car on, and it didn't like to idle. Eventually the SOC meter went to zero and the car absolutely wouldn't idle. In fact, there was this weird behavior where: I turn the key, the car idles for about 1.5 seconds. The car stalls. The car comes back (as from an auto-stop) and idles for 1.5 seconds. This repeated with no intervention from me, until I took the key out of the ignition.

Well, a look under the hood revealed that _both_ the grounding cables had snapped. I can only assume that one snapped a while ago and the other was compensating, until it, too, went. Can anyone guess what would happen if one or the other ground was not present?

I've read this thread:

http://www.insightcentral.net/forum/vie ... php?t=3196

and intend to get some paste intended for creating an electrical connection between dissimilar metals. But in the meantime, my car still does not go.

I reconnected the grounds: the engine ground / sub ground with a 6-awg wire I had & the original nuts, and the transmission ground with my jumper cables. With that done, I hear the starter motor engaging and the engine turns over, but doesn't fire. I suspect that the tranny ground connection I made with the jumper leads isn't that good, so went out to get more 6-awg wire and crimp ends. But I'm not convinced that that connection would keep the engine from firing.

I have the shop manual (which hasn't been much help to this problem), but I don't have the "Electrical Troubleshooting" manual.

I'm mighty confused at this point. I don't know that much about cars --- never owned one before this Insight. For all I know the problem could simply be that I flooded the engine, by giving it gas when it was running on assist-only (before I realized that the ground cables had snapped). But I'm an electrical engineer, so I'm going to clean the electrical leads and get out there with cable, crimpers, and a voltmeter/ohmmeter to see if I can fix the problem.

I suspect that the engine isn't firing because the computer thinks it shouldn't. I've seen this happen on an old volvo before. due to a bad electrical connection to that car's microprocessor.

Well, that's my story. My questions are:

Does anyone know why there are two ground cables, or what specifically the "transmission ground" is for?

Does anyone know enough about the computers' state machine to explain why the car would let itself run on assist only, or other consequences of running the car with no engine or transmission ground?

Thanks very much,

Karen

 

[Dougie]

It's not clear why there are two ground wires. It may have something to do with the factory assembly process.

In any case, given the electrical trauma you car has been under, it's probably worth doing all of the resetting procedures in the manual, after cycling the main power switch. Just on the general "reboot the system" principle.

 

[The Citrus Smoothie]

Don't take this the wrong way , but I thought I ought to check:

"The initial symptoms were that the car stalled as I was going around a corner, then seemed to require more gas than it should have to travel on flat ground, and assist was even kicking in on flat ground. The sound of the engine turning over was muted each time I turned the car on, and it didn't like to idle. Eventually the SOC meter went to zero and the car absolutely wouldn't idle. In fact, there was this weird behavior where: I turn the key, the car idles for about 1.5 seconds. The car stalls."

Sounds as though you might of run out of petrol :?: Or alternatively perhaps have a blocked fuel filter / gunk in the tank?

Just my 2 pennies....

 

[Insightful Trekker]

<snip>

Well, that's my story. My questions are:

Does anyone know why there are two ground cables, or what specifically the "transmission ground" is for?

Does anyone know enough about the computers' state machine to explain why the car would let itself run on assist only, or other consequences of running the car with no engine or transmission ground?

Thanks very much,

Karen

As an electrical engineer I hoped you'd have the answer. I don't think there's a valid design reason except for redundancy. And it appears it kept you going a few more miles :!:

Assist is _supposed_ to do just that (give assist) on acceleration. I don't think the system is "smart" enough to realize the ICE (Internal Combustion Engine) had "died".

Not sure of some of the other ground locations and the possible overload (Read, Smoke :!: ) from loosing the big'uns. Basically any of the smaller ground that attach to the engine could have been overloaded. G101 is the main ECM ground and is located on the engine block, under the "beauty" cover and just to the left (driver's side) of the oil filler cap. Severe overloading of these wire(s) can cause cross circuiting in the looms and damage to other components. ($$$) If the insulation is visibly "blistered" near the ground screw points then further inspection is highly advised before any more key on time :!: :!: :!:

HTH!

But I'd still recommend investing in an ETM (for the future)

 

[krobinso]

Don't take this the wrong way , but I thought I ought to check:

Sounds as though you might of run out of petrol :?: Or alternatively perhaps have a blocked fuel filter / gunk in the tank?

Just my 2 pennies....

Never bad advice =) It's one of the first things I looked at, though, and the fuel tank is almost full.

The other first things I checked include: oil level / consistency OK, engine temp shown as low on dashboard, engine coolant level OK, fuses OK (the ones that were easy to check & the ones that looked relevant to IMA or starting)

I now think that the difference between engine-turning-over-on-starter-motor behavior and going-in-and-out-of-idling behavior could be attributed to the 144-v battery being almost dead or totally dead. i disconnected both batteries in an attempt to reset the computer, and afterwards i was getting the idle - no idle - idle behavior again. this stopped when i turned off the 144-v battery, and the car went back to turning over the engine but not firing.

Now looking into ECM reset procedures ... but not confident that a reset procedure will convince the ECM to get the engine to fire ...

 

[Dougie]

If it starts, there is also an "idle learn" procedure you have to do... I think you have the shop manual so you should be able to find it...

 

[krobinso]

Yes, I did find the idle learn procedure. But I did not find any initialization procedures that can be done without the engine firing. I suppose the next thing to check is connections to the spark plugs. Hopefully the problem isn't that the whole ECM is fritzed. (I'm not sure why that would have happened, unless its not having a ground was somehow enough.)

 

[krobinso]

fwiw:

there is no obvious damage under the engine's plastic cover: no electrical lines with melted insulation, for instance.

and when the engine turns over without firing, i can smell unburned gas in the exhaust. this is why i think the problem is with spark plugs or signal to the spark plugs, rather than a blocked fuel line.