ESS and battery voltage problems - JeepForum.com
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post #1 of 21 Old 12-04-2020, 08:00 PM Thread Starter
Mangoh
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ESS and battery voltage problems

Hello everyone. I'm new to this forum. I recently have been having trouble with my 2017 jeep grand cherokee limited 4x4. It started with erratic battery voltage indicated on my dash. Sometime it would read 14v, 13.6, and now 12.7. And now my ESS won't work and it gave me the warning to "stop safely, engine will turn off soon". I checked the voltage at the battery terminal and it read 12.6 when then engine is off, and 14.2 when engine is running. But the dash still says battery voltage is only 12.7. Does anyone have an idea of what the problem could be?

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post #2 of 21 Old 12-04-2020, 08:35 PM
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There are a couple threads describing that the voltage regulator is smarter than the average and voltage is not constant, it will vary under different driving and battery conditions, the side effect of saving 0.1 mpg. The regulator senses battery condition and only calls for a charge (observed as higher voltage) when it senses the battery needs it. What you are observing may be normal.

The dash and battery voltage should indicate the same unless there is a bad ground, there is a thread around here somewhere on that. If you can't find it or no one jumps in here by the time I get back I'll try to search for it. Where are you measuring the battery voltage, between the battery + terminal and chassis ground?

I just got lost in thought. It was unfamiliar territory;
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
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post #3 of 21 Old 12-04-2020, 10:23 PM Thread Starter
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I tested the voltage at the battery terminals of both batteries, under the hood at the chassy ground, and the power distribution center. I will check out to see if there is a problem with the ground.
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post #4 of 21 Old 12-04-2020, 10:47 PM
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Here’s a link that may help:

https://www.jeepforum.com/forum/f309...topics/4374529


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post #5 of 21 Old 12-05-2020, 06:59 AM Thread Starter
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That could explain the battery voltage but it doesn't explain why the car says the ESS isn't working and to stop the vehicle cause then engine is going to turn off.
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post #6 of 21 Old 12-05-2020, 08:40 AM
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I had an issue with my ESS about a year ago, as well (2017 Altitude). It stopped working around 30k miles and gave me the reading “Start/Stop Not Ready”. My battery voltage looked normal. Brought to the dealer and they replaced the small battery, saying it was bad.

That worked for about a week, then the ESS stopped working again. Voltage looked normal. Back to the dealer. Main battery tested bad. Replaced. No issues since.

Don’t know if the main battery was the culprit all along or both were bad. Hope this helps.

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post #7 of 21 Old 12-05-2020, 09:09 AM
ColdCase
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Quote:
Originally Posted by Mangoh View Post
That could explain the battery voltage but it doesn't explain why the car says the ESS isn't working and to stop the vehicle cause then engine is going to turn off.
I don't recall anyone here report seeing a "stop safely, engine will turn off soon" message. An everyday OBD scanner may be able to read relevant DTC codes which would be helpful, most parts stores read codes for free.

We may be jumping to the conclusion that its an electrical problem, but that is indicative of one or the other battery failing, or perhaps a charging or ground connection problem.

Usually you get no warning until the dash lights up like a Christmas tree. Looks like for this case they are giving you some warning.

I just got lost in thought. It was unfamiliar territory;
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
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post #8 of 21 Old 12-05-2020, 11:41 AM Thread Starter
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This morning when I went out to my car, turn the car to acc and turned everything in the car off. It told me my voltage was at 10.2. But when I checked the voltage at the battery terminal, it was 12.6. I changed out the Aux battery last night and it didnt solve the problem. I will try replacing the main battery to see if that works.
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post #9 of 21 Old 12-05-2020, 01:43 PM
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Quote:
Originally Posted by Mangoh View Post
That could explain the battery voltage but it doesn't explain why the car says the ESS isn't working and to stop the vehicle cause then engine is going to turn off.

I just did a quick web search for “grand cherokee stop safely, engine will stop soon” but no Grand Cherokee links were returned. Several JlLWrangler and Compass links with a 13 page JL Wrangler forums discussion about this problem.

JL Wrangler Forums › threads › sto...Web results"Stop Safely Vehicle Will Shut Off Soon" | 2018+ Jeep ...

Possible causes listed were shorted power steering pump, alternator, bad auxiliary battery/main battery, loose grounds and cable connection, defective PCM, loose and open fuses (mainly the 150 amp buss fuse located in the fuse box). The buss fuse discussion starts on page 6. The JL fuse box looks nothing like my GCTH but the discussion may give you help with your diagnosis.


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post #10 of 21 Old 12-05-2020, 02:53 PM
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Yeah there could be something loading down the battery bus, like the power steering pump. That will drop voltage. May want to try something like pull the power steering pump fuse and see if the bus voltage remains stable.

Just to note that anything that prevents ESS from working, like a diagnostic code, will give you ESS not working status. Doesn't mean there is an ESS problem, just that it won't activate.

I just got lost in thought. It was unfamiliar territory;
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
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post #11 of 21 Old 01-15-2021, 09:26 AM
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Jeep Smart Charging system

Attached is a Jeep Star Online Publication pdf partly explaining the Jeep Smart Charging System.
Case #S2008000031

Date Announced:
APR 04, 2020
NHTSA ID:
#10175657

Low Charging Voltage Displayed On Cluster

Link to original Document:

https://static.nhtsa.gov/odi/tsbs/20...75657-9999.pdf
Attached Files
File Type: pdf Jeep smart charging system-MC-10175657-9999.pdf (143.4 KB, 6 views)
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post #12 of 21 Old 06-09-2021, 06:44 AM
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I don't see anything in this thread that says the battery charging light ever comes on. Does it?

I've had this intermittent problem since last year, actually longer, where the Red Battery light and the Yellow ESS Start/Stop lights come on at the same time, always both and always together. The battery voltage is usually around 12.x when this happens Turning off the motor and restart, and the lights are out, and the battery voltage is a bit higher in the low to mid 13's. In the fall of 2019 the dealer changed out the batteries and it fixed it through the winter, but as soon as the temps got hot again in early last summer, it started doing the same thing. No codes. I thought it might be the alternator so I had it checked with the attached result (some have seen this before), which appears to indicate the alternator isn't producing as it should. Just prior to my dealership appointment I was hit with a COVID quarantine due to direct contact tracing (I never did get it), and had to cancel the appointment. By this time it was late last fall with the cold winter coming in. The problem went away, again! Until now. It's been a late spring and the hot temps here in Korea have just started, and sure enough a week ago the same problem. And in the last few days when it's been really hot, it happens sometimes 2 times a day.

Mangoh, anything here sound familiar to you, or anyone?
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Previous 83' CJ-7, 77' J-10, 75' CJ-5
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post #13 of 21 Old 06-09-2021, 07:02 AM
ColdCase
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Perhaps the temperature sensor at the battery terminal is out of calibration, reporting a higher temperature, and the PCM is cutting back on the alternator? Or perhaps another temperature protection circuit.

I just got lost in thought. It was unfamiliar territory;
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
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post #14 of 21 Old 06-09-2021, 01:40 PM
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Quote:
Originally Posted by ColdCase View Post
Perhaps the temperature sensor at the battery terminal is out of calibration, reporting a higher temperature, and the PCM is cutting back on the alternator? Or perhaps another temperature protection circuit.
Temperature sensor at the battery terminal? I didn't know there was one that's good info thanks. Under the seat right at the battery right? That would answer the question I've been asking myself about why the under hood temps would even make temperature an issue. Do you know of a test for this sensor?

2017 Grand Cherokee
1994 Wrangler SE
Previous 83' CJ-7, 77' J-10, 75' CJ-5
Stationed in Korea
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post #15 of 21 Old 06-09-2021, 02:26 PM
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Thinking out loud here.... By 2017 the battery sensor/IBS, 56029778AB, includes a temperature sensor, I think. The intelligent battery sensor (IBS) gives precise and on-demand current, voltage and temperature (IVT) measurements from the battery.

Many electrical problems, including issues with the battery current sensor can be caused by loose or corroded battery terminals or moisture/corrosion around the battery sensor. To function properly, the battery sensor must be clean and dry, and the pole terminal must be tight.

A battery sensor is a fragile device and can also be damaged when servicing or removing the battery.

The sensor is like $15 at discount, so most here just change them when suspect. If your scanner can read the values from PCM data, and they don't make sense, that may give a clue. There is probably a procedure in the FSM, but I don't have access here to one that covers 2017.

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I just got lost in thought. It was unfamiliar territory;
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
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