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2018 Grand Cherokee Battery Drain & 'Service Shifter' Message

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Sarah K. · rep 0 · May 22, 3:25 AM · 1 replies · solved · Question

Vehicle: 2018 Jeep Grand Cherokee Limited

Hey everyone, I'm having a persistent issue with my 2018 Jeep Grand Cherokee Limited. For the past few weeks, the battery keeps draining overnight, sometimes completely dead. I've had to jump-start it multiple times.

What's really weird is that sometimes after starting it, I get a 'Service Shifter' message on the dash, and the start-stop system hasn't been working at all. I had the battery tested, and they said it's good, but it just keeps dying. Could this be an alternator issue, or something else electrical drawing power?

I'm worried about getting stranded. Any ideas on what could be causing this phantom drain and the shifter message?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:25 AM

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ClearTheCode admin answer:

This sounds like a classic parasitic draw combined with potential low voltage issues affecting multiple modules. The 'Service Shifter' message is a common symptom when the battery voltage drops too low, as the electronic shifter module requires stable power.

Possible Causes:

  • Parasitic Draw: A module or component is staying awake and drawing power even when the vehicle is off. Common culprits include the Uconnect system, a faulty door switch, glove box light, or even a failing relay.
  • Failing Alternator: While the battery tested good, a weak alternator might not be fully charging the battery, leading to a gradual discharge.
  • Faulty Battery Sensor: The Intelligent Battery Sensor (IBS) on the negative terminal can sometimes fail, providing incorrect charging information to the Powertrain Control Module (PCM).
  • Software Glitch: Less common, but sometimes a module requires a software update to resolve power management issues.

Troubleshooting Steps:

  1. Check for OBD Codes: Even if no check engine light is on, scan for stored codes, especially in the BCM (Body Control Module) and PCM. Look for codes like P0562 (System Voltage Low) or U-codes related to module communication.
  2. Perform a Parasitic Draw Test: This involves connecting an ammeter between the negative battery terminal and the negative battery cable. After letting the vehicle 'sleep' (usually 30-60 minutes), the draw should be under 50mA. If it's higher, start pulling fuses one by one to isolate the circuit.
  3. Inspect Alternator Output: Have the alternator's output voltage and amperage checked under load to ensure it's charging correctly.
  4. Inspect Battery Terminals: Ensure they are clean and tight, as loose connections can mimic battery issues.

When to See a Shop:

If you're uncomfortable performing electrical tests or can't pinpoint the source of the draw, it's best to take your Jeep to a qualified technician. Diagnosing parasitic draws can be time-consuming and requires specific tools and knowledge. They can also perform advanced diagnostics on the IBS and Uconnect system.

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