Beedo
Member
- Joined
- Jul 17, 2024
- Threads
- 6
- Messages
- 22
- Reaction score
- 22
- Location
- Dominican Republic
- Vehicle(s)
- JLU Sport
- Thread starter
- #1
JL Sport with 3.6 Pentastar, 110,000 km, with offroad use. Unrelated to climate, tropical island.
The issue started after offroading. I began getting intermittent long cranks (2–3 secs), no check engine light, no engine codes, but did get an ESS unavailable message on the dash. Once the engine started, the Jeep drove perfectly, no power loss or drivability issues. Restarting after driving was usually smooth.
At one point I had a start where the engine fired, RPM rose, then dipped briefly. Around the same time, the brakes/ESC briefly grabbed only when reversing at low speed. Throttle body and air filter were cleaned due to dust, which made no difference.
Battery-related work was then done. I’ve since confirmed that the aux battery was physically removed and that the old aux battery was swollen. After this work, starting improved significantly, the ESS message disappeared, and ESS currently works.
However, the issue is still not fully resolved. If I press and hold the start button for about one second, the engine starts smoothly. If I do a quick tap and let the Jeep handle the start sequence, it does start, but you can feel and hear it struggle slightly. Once running, the Jeep drives amazingly, like nothing is wrong.
Generic OBD scans show no engine codes. There are no stalls, no loss of power, and no drivability problems once the engine is on.
My concern is that the aux battery was removed but the system may be spoofed or partially deleted, allowing ESS to remain active while the vehicle is effectively running on a single battery. This feels like voltage instability during the crank/start transition rather than fuel, spark, or compression.
Looking for input from anyone who has seen tap-vs-hold start behavior on a JL, ESS working without a physical aux battery, or ABS/ESC odd behavior caused by voltage issues. Also looking for guidance on the correct way to resolve this cleanly (proper delete vs restoring factory setup).
Thanks in advance.
The issue started after offroading. I began getting intermittent long cranks (2–3 secs), no check engine light, no engine codes, but did get an ESS unavailable message on the dash. Once the engine started, the Jeep drove perfectly, no power loss or drivability issues. Restarting after driving was usually smooth.
At one point I had a start where the engine fired, RPM rose, then dipped briefly. Around the same time, the brakes/ESC briefly grabbed only when reversing at low speed. Throttle body and air filter were cleaned due to dust, which made no difference.
Battery-related work was then done. I’ve since confirmed that the aux battery was physically removed and that the old aux battery was swollen. After this work, starting improved significantly, the ESS message disappeared, and ESS currently works.
However, the issue is still not fully resolved. If I press and hold the start button for about one second, the engine starts smoothly. If I do a quick tap and let the Jeep handle the start sequence, it does start, but you can feel and hear it struggle slightly. Once running, the Jeep drives amazingly, like nothing is wrong.
Generic OBD scans show no engine codes. There are no stalls, no loss of power, and no drivability problems once the engine is on.
My concern is that the aux battery was removed but the system may be spoofed or partially deleted, allowing ESS to remain active while the vehicle is effectively running on a single battery. This feels like voltage instability during the crank/start transition rather than fuel, spark, or compression.
Looking for input from anyone who has seen tap-vs-hold start behavior on a JL, ESS working without a physical aux battery, or ABS/ESC odd behavior caused by voltage issues. Also looking for guidance on the correct way to resolve this cleanly (proper delete vs restoring factory setup).
Thanks in advance.
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good luck
