Diagnostic Case Study

Degraded Pack, Dead Module Sensors & Warm A/C

A 2020 Jaguar I-Pace EV (185k km) presented with a range complaint and an A/C that stopped getting cold. There were no warning lights on the dash.

The Challenge

This case tells three stories from one set of scans: a degraded HV pack, compromised thermal sensing and an A/C that won't cool. The first scans showed no fault codes, because our reports weren't yet reading the battery module's own. A later scan with a third-party tool found P1B48 active, consistent with the H441 recall.

Correlating the live OBD channels across the battery and climate systems showed what the codes hadn't.

Structuring the Diagnostic

By adopting a structured and documented approach, the owner could have used the EvmetricsOBD Workshop Templates to guide the diagnostic process. These templates lead the technician through a strict hierarchy of tests, ruling out causes logically and preventing expensive misdiagnoses.

EV HV Battery Recall & Thermal Integrity

Correlate pack health, per-module thermal sensing and the shared cooling loop — for degraded packs, recall checks, and EV A/C-won't-cool complaints
  • Recall / TSB check
    Verify the VIN against open HV-battery recalls (e.g. I-Pace LG-cell fire risk) and record the current BMS software level
  • Capacity vs Power Health
    Read both from the BMS. Capacity fade with full power and tight cells = uniformly aged pack, not a single weak cell
  • Cell voltage spread
    Confirm highest-vs-lowest cell is within spec; a wide spread points at a failing cell rather than even aging
  • Module temp sensor sanity
    Compare every per-module temperature against pack Min/Avg/Max; flag any stuck/floor (e.g. −15 °C in a warm pack) or flapping channels as failed thermistors
  • HV isolation / sense rails
    Check the BECM HV-sense voltages are steady and consistent; intermittent 0↔400 V flapping indicates an isolation or sense-wiring fault
  • Battery thermal management (BTMS) loop
    Confirm the refrigerant/coolant loop is cold AND that cooling actually reaches the pack; check the BTMS heat exchanger and its expansion/thermal-management valve
  • Cabin-cool cross-check
    If the A/C won't cool, check the refrigerant charge first, then air-side distribution and the shared BTMS valving. Mark N/A if there's no A/C complaint.
  • Gate: HV De-energization
    Before any module or pack work, complete the HV System De-energization protocol (PPE, isolation, capacitor bleed, zero-volt verification)
The Outcome The structured approach exposed a battery pack with uniform aging and failing thermistors, the profile behind a known recall, and gave the owner a data-backed reason to push for a warranty/recall assessment. The A/C is a separate question: the refrigerant reading first used to rule out a regas turned out not to be a real sensor, so a low charge is now the first, cheapest check.