High ECM Voltage (over 16V), periodic.

[MichaelOverfield]

I recently replaced the original batteries, they were approaching 7 years, still cranking OK, but I was seeing more strained starting, and bigger voltage swings with the grid heaters so figured best to replace before failure and save the rest of the starting and charging systems the strain of weak batteries. I found Odyssey AGMs performance series with a discount at Autozone for the replacements.

I expected fewer voltage swings with fresh batteries, but I'm still seeing the occasional spike to above 15.5 volts. One alarm came in at just over 16 volts! I have the Ultra-guage connected and it monitors all kinds of parameters and alarms on high ECM voltage, capturing the alarm voltage value.

This only occurs shortly after start up, usually during the cycling off of the grid heaters..

I'm concerned that such voltage spikes could damage electronics, or other components. Has anyone else seen similar voltage swings, and if so, what have you found to be the culprit, or is this typical..


Thanks.

 

[PWong]

seeing the occasional spike to above 15.5 volts. One alarm came in at just over 16 volts! I have the Ultra-guage connected and it monitors all kinds of parameters and alarms on high ECM voltage, capturing the alarm voltage value.

This only occurs shortly after start up, usually during the cycling off of the grid heaters..

This was absolutely normal in the COLD/FREEZING morning after start up and before driving it over 15mph.

 

[Ozymandias]

Electronics work on 5V, but could hurt the power source.
I would check this with a DRBIII, maybe there is a problem within the charging system.

 

[PWong]

5V power supplies (two) were built in the ECM.
The output should be a constant 5V, irrespective of the variable B+ input.

I saw 16.3 V once this morning!
It's just the overshooting of the voltage when the grid heater cycling off.

 

[Ozymandias]

I think so, maybe the Ultra-Gauge is to picky on short spikes.

 

[MichaelOverfield]

Thanks for the replies.. in a related event, I got a voltage spike on a different car, perhaps it is just having the ability to monitor and alarm with the UltraGauge. That too was shortly after start up, but no grid heaters and perhaps the biggest load being the rear window defroster. Maybe its actually pretty typical, but not seen on the installed gauge displays since it is such a short duration voltage spike.. Will keep monitoring I guess.

 

[PWong]

I guess the max ECM target voltage was 15V, at least at my climate region.
I would start to worry if I see the voltage constantly over 15V without the grid heater operation.

 

[Ozymandias]

Mine goes with 15.2 all the Time in great cold.

Commanded from the ECM and executed by the Alternator.

 

[Wayne M.]

I always thought there was a perceived target battery temp and that the PCM has algorithm to maintain that through charging functions. I know there's such language in the FSM. What is an Ultragauge?

 

[MichaelOverfield]

Here is a link to the Ultraguage: http://ultra-gauge.com/ultragauge/index.htm

It is an inexpensive way to get display of over 100 engine parameters and you can customize 7 screens for display and enter high and low alarms for each item. I can also clear a CEL when needed.

 

[Wayne M.]

Looks pretty good. Does it show rail pressure and real oil pressure?

 

[MichaelOverfield]

It does read fuel rail pressure, also turbo boost, EGR position and error, Cat Temps (I can now know when a Regen event is in progress) and many other parameters. I don't recall seeing oil pressure as one of them, it is based on OBD2 parameters.

 

[PWong]

It would not display the correct boost reading on my truck when the boost was over 23psi because of wrong scaling factor.

 

[Wayne M.]

Looks good.

 

[MichaelOverfield]

It would not display the correct boost reading on my truck when the boost was over 23psi because of wrong scaling factor.

That is interesting, should I expect to see the stock turbo even go up to 23psi? I don't recall ever seeing it that high, or even close, but then again, could be due to the error you describe. What I do see that is odd, the boost displays negative for times when in regen. It also goes up with exhaust braking, but that latter seems expected.. Not sure what is the deal during regen, perhaps to help boost the EGTs to get the DPF clean out going.. not sure.

 

[PWong]

That is interesting, should I expect to see the stock turbo even go up to 23psi?

Expect to see lower 30s at WOT.
I saw 22.34 psig max.
Otherwise the Ultragauge was a very good product for that price.

 

[MichaelOverfield]

Expect to see lower 30s at WOT.
I saw 22.34 psig max.
Otherwise the Ultragauge was a very good product for that price.

Good information, thanks.. I'll keep a closer eye on it, but appears you are correct in that it reads boost pressure off a bit, I thought it odd that it would read a negative during regen, perhaps its just a lower positive and the scaling factor explains the odd reading.. but while the numbers may be off, I think the change and direction remains useful, but the most valuable thing I find is the ability to monitor regen events, and to read and reset trouble codes, especially EGR codes...

 

[MichaelOverfield]

Well, I had another post with high voltage over 16 volts... it turns out the Odyssey AGMs were bad, apparently some issue from new. Replaced them at about a year, under warranty, and the replacement set are not showing the high voltage swings that the last set did.. and so far so good, I just did an over 4000 mile trip, towing at highway speeds, many starts and stops, all kinds of weather from desert heat to mountain snow, yes, even on May 6th! Thought that was crazy... the new batteries seem to be working normally, even with the cycling grid heaters when in operation.