I have a friend with a 2001 Cadillac Deville and it seems that everything is controlled by electronics in this car. It is like the engineers went the extra step to make the systems more complicated than needed. It began to really act funny yesterday. The car began saying it was going like 170MPH and started to speed up on its own. All the other sensors were displaying really odd numbers that made no sense. The air temp was -10, the tire pressure was 600psi, and so on. EVERYTHING was reading out like this.
I disconnected the battery for a while and reset the ECM. Everything seems normal now but is this a sign of something failing or a random incident? If so, what is likely failing?
Follow @knfenimore advice. If the trouble happens again I would suggest you check to see if the alternator is putting out excessive AC ripple voltage. It shouldn’t exceed 0.1 volt AC while the engine is running around 1,500 RPM if the alternator is ok. If there is a BCM module controlling all those things you mention, that would be a suspect also.
The battery is actually under the backseat so everything looked really clean. I did pull both terminals and put them back on to make sure the connection was ok. The car has around 100k or a little more on it so the alternator might be getting a little old. I don’t remember what needs to be removed to get to the alternator but suspect it isn’t just right on top like on most vehicles.
If it happens again, I will test the alternator for ripple currents and then have her take it to the dealer as I know replacing any electronic modules involves specialized re-programming.
I wish they didn’t have to make cars so complicated. Somehow they convince people to pay extra for this stuff!
True, yet many things on cars just ten years ago were controlled by a mechanical system that was easy to service. In this case, one part fails and the entire car goes haywire! The Cadillac Northstar based cars are not well-liked by anyone who has serviced them.
I didn’t hook up a voltage tester but put the onboard display to battery voltage and watched it. It usually sat at 14.4 volts but ranged from 14.1 to 15.0 volts. All these numbers seem a tad high and am wondering if the voltage regulator in the alternator is going out. Do you think this is the culprit? It doesn’t look like this is a common problem from my research.
The DC charging voltages you show are okay, right where they should be. The issue I was talking about is the AC voltage. There should be less than .1 volt of AC voltage across the battery while the engine is running and there is a current good load on the alternator.
Ok, I will break out the multimeter and use this for the test. Should I try to put as much load on the alternator as possible? Like have the lights on and AC blowing on full?
The car hasn’t acted up since the reset where I unhooked the battery. Maybe it was an isolated incident.
“Should I try to put as much load on the alternator as possible?”
No, just a moderate load.
Cleaning the terminals might have done the trick.
The mating surfaces are most important, not the outside surfaces you can see when the cables are attached.
The battery acts as a reservoir to smooth out the DC voltage.
It doesn’t do that so well if the terminals aren’t clean and tight.
Another thing to be aware of when checking the AC voltage is knowing if your meter blocks the DC component or not. If you see a AC voltage around 22 volts then check the battery voltage while the engine is off. If you still show any AC voltage reading then your meter isn’t blocking the DC component. You would need to put around a .5 microfarad capacitor in series with one of the test leads in order to block the DC.