J-Scan OBD guide

• Use an adapter from J-Scan's verified compatible list — Bluetooth is preferred over Wi-Fi.
• iPhone: the adapter MUST be Bluetooth 4.0 (BLE) or newer; older BT dongles won't pair.
• Wi-Fi adapters often force your phone off mobile data — buy your license before connecting if you use one.
• Avoid cheap/generic ELM327 clones; many are only partly functional.
• Sanity-check any adapter with Settings → ELM327 Identification (all-green is good).

1. Install JScan free from the App Store / Google Play.
2. Optional: open Demo Mode (pick the vehicle, choose Demo Adapter) to preview Liberty functions with no car connected.
3. Plug the adapter into the OBD-II port — under the dash, driver's side, just left of the steering column.
4. Turn the key to ON/RUN so the dash lights up (ACC is not enough; engine off for adaptations).
5. Open JScan → select Jeep Liberty → Autoconnect (or pick your adapter; mind BLE vs older-BT groups).
6. Grant Location permission and keep GPS on.

Free

• Connecting
• Quick Diagnostic (generic check-engine codes)
• Generic Live Data
• Viewing current adaptation / ECU values

Needs a license

• Advanced Scan (all-module DTC sweep)
• Per-module Live Data & Trail View
• Writing any change to the ECU (adaptations / configuration)

• Dashboard — Quick Diagnostic (free engine codes), Live Data, and Advanced Scan (all-module sweep, license).
• Modules — pick any module for Trouble Codes, Live Data (choose PIDs → press PLAY), Activations (trigger actuators), and Configuration.
• Adaptation — the curated list of settings you can change on the Liberty (search at the bottom).

• Adaptations are permanent config changes (tire size, lighting…) that persist after you unplug.
• Module → Configuration is read live from the module: if an option isn't listed, your module doesn't have it.
• An Activation is a temporary live trigger — it is NOT saved after a restart.

Trace & Restore (in Settings)

• On first connection J-Scan records your original values.
• Trace = full history of every change; Restore = roll back all or part to the originals.

• Warm the engine to operating temperature first — cold readings (open-loop) look 'wrong' on purpose.
• Graph only 1–3 related PIDs at once and watch the trend, not a single snapshot.
• Compare against a known-good value (the tables below) or the other bank/cylinder/wheel.
• Use J-Scan's record/log while the fault happens (idle, road test, or the moment a code sets), then scrub back.
• Change one variable at a time (e.g. snap throttle, create a small vacuum leak) and watch which PID reacts.

Misfire (per cylinder)

Fuel, air & temperature

Oxygen sensors

Throttle, ignition, EVAP & charging

Transmission — 42RLE (under PCM / Trans)

ABS & charging

• Watch the per-cylinder misfire counters (you already do this) — a single cylinder climbing isolates the problem to that hole.
• Same cylinder always: swap its coil and plug with a neighbour; if the misfire follows, it's that part; if not, suspect injector or compression.
• Misfire that moves or is random on several cylinders: look at fuel trims (lean?), MAP (vacuum leak?), and fuel pressure before condemning coils.
• Cross-check O2/short-term trim spikes timed with the misfire counts, and knock retard.

• Classic signature: LTFT strongly positive (lean) at idle, but returns toward 0 as rpm rises — unmetered air matters most at idle.
• MAP reads higher than ~20–35 kPa at warm idle (less vacuum) and idle may hunt.
• Confirm: briefly add propane/throttle-body cleaner near intake/gaskets and watch STFT drop (rich) at the leak.
• A leak after the throttle (PCV, brake booster, intake gasket) leans idle; also check the EVAP purge isn't stuck open.

• Lean everywhere (LTFT high + at idle AND cruise): low fuel pressure (should be 58 ±5 psi), tired pump, clogged filter, or weak injectors.
• Rich everywhere (LTFT strongly −): high fuel pressure, a leaking/stuck injector, or a skewed ECT/MAP making the PCM over-fuel.
• Compare bank 1 vs bank 2 trims: if only one bank is lean, suspect that bank's injector(s), O2, or a bank-specific leak.
• Verify the upstream O2s are actively switching; a lazy O2 mimics fuel problems.

• Cold-soak plausibility: after sitting overnight, ECT and IAT should read nearly the SAME and match ambient — if not, one is bad.
• MAP sanity: key-on/engine-off it should read barometric (~95–101 kPa); if it doesn't, the sensor or its vacuum source is suspect.
• TPS/APP sweep: roll the throttle slowly 0→100% and watch for a smooth rise with no dead spots or sudden drops.
• O2: a good upstream sensor crosses rich/lean several times per second at 2500 rpm; a flat or slow trace is worn.

• Watch ECT climb and plateau near 88–104°C (190–220°F); a steady climb past that with the fan not commanded points to fan/relay or coolant flow.
• ECT that never reaches ~90°C (stuck open thermostat) keeps the engine in open-loop and rich, hurting economy.
• Compare ECT to IAT at a cold start — they should start equal; a large gap at cold start means a sensor is off.
• If ECT spikes then drops erratically, suspect air in the system or a failing sensor, not always a real overheat.

• TCC slip should fall to ~0 rpm when the converter clutch locks at steady cruise; a held 100–300 rpm slip = worn converter clutch.
• Compute gear ratio from input ÷ output speed and compare to the commanded gear; a mismatch under load = clutch/band slip.
• Watch TFT — sustained high fluid temp accelerates wear and can drop the trans into limp/2nd-gear-hold.
• Erratic line/governor pressure with rpm points at the solenoid pack or pressure sensor rather than the clutches.

• In the ABS module, graph all four wheel-speed PIDs and drive a steady speed — all four should read the same.
• One wheel reading zero, lagging, or jumping = that sensor, its tone/reluctor ring, or wiring (often the cause of a random ABS/ESP light).
• A wheel that only drops out over bumps points to a damaged tone ring or loose sensor.

• Command the purge solenoid and watch fuel-tank pressure respond; no change suggests a stuck purge, bad LDP, or a blocked line.
• A small-leak code (P0456) with otherwise-normal trims is usually the gas cap, a hose, or the LDP — not a fuel-delivery fault.
• Run the EVAP/LDP test with a cool tank and roughly half a tank of fuel for a valid result.

1. Connect, then open Adaptation → TPMS settings.
2. To disable: set 'TPMS On/Off' / 'Premium TPMS present' to deactivated, or 'TPMS Configuration' → 'Other – Disable Warning'.
3. To change thresholds: set the EVIC-version threshold and adjust 'Max Load Inflation Pressure Front/Rear' (the low-pressure trigger); leave 'Light Load' at 0.
4. Reset: lock the car a few minutes; if nothing changes, briefly disconnect the battery or run '!Restart all ECUs'.

1. Engine OFF. Connect, open Adaptation → Tire & Axle settings.
2. Set Tire Size from the dropdown (value = tire diameter in inches).
3. Tip: choosing ~0.5 in smaller than actual makes the speedometer match GPS.
4. Avoid the manual-entry field (it's circumference in mm and easy to get wrong).
5. Disconnect and let the car sit a few minutes — no ECU reset needed.

1. Confirm the accelerator pedal operates correctly.
2. Connect to the vehicle.
3. Open Adaptations → Vehicle Maintenance.
4. Run 'ETC Relearn' and follow the prompts.

1. Connect; open Adaptations and search 'LED'.
2. Enable 'LED [light type] Present' for every position you're converting.
3. If a position has no setting, the software can't support it — use a resistor / anti-flicker harness.
4. Optionally disable the matching 'lamp out' DTC; for LED DRLs set DRL/headlamp voltage to 12–14 V.

1. Engine OFF, ignition in RUN.
2. Open Adaptations → DRL settings.
3. Set 'DRL Configuration' to 'Canada DRL' and update the ECU.
4. Set 'DRL Location' to 'Low Beam' and update the ECU.
5. Test: start, release the parking brake, shift to Drive.

1. Adaptations → run 'ORC – Un-Initialize'.
2. Run 'ORC – Clear All Data'.
3. Modules → Airbag → Trouble Codes → delete errors.
4. Run 'ORC – Initialize'.

Used ABS module

1. The used module's part number must match the original exactly.
2. Advanced Scan: confirm no ABS faults except 'Vehicle Configuration Mismatch'.
3. Adaptations → Vehicle Maintenance → run 'ABS – Clear VIN Original and Current'.
4. Ignition OFF a few minutes → RUN (don't start), reconnect.
5. Run 'ABS – Initialization (Full)', cycle ignition, then verify the new VIN in Modules → ABS.

Used BCM (Body Control Module)

1. First back up the ORIGINAL BCM: Settings → Trace Entry → Store, then Restore → ⋮ → Start Backup.
2. Fit the used BCM; connect. Modules → Body Module → Configuration: set 'Vehicle Configuration Status' = False.
3. Adaptations: run 'Reset Configuration', then 'Engineering Configuration Reset'.
4. Settings → Restore → pick your backup → restore all settings.
5. Cycle ignition OFF→RUN, reconnect, set 'Vehicle Configuration Status' = True to lock it in.

1. Read the PIN: connect with a working key, Adaptations → 'PIN Reading – BETA', select the matching WCM, run it.
2. Turn the car OFF; insert the new cut key and turn to RUN (don't try to start).
3. Connect; open 'Ignition Key Programming – BETA', select the same WCM, run it and follow prompts.

1. Key in RUN, not ACC.
2. Use a supported adapter (iPhone needs BLE 4.0+); phone Bluetooth/Wi-Fi on; grant all permissions incl. Location.
3. Select the correct adapter; use Auto-connect only with BLE adapters.
4. Close or uninstall other OBD apps (Torque, OBDLink…) — they hijack Bluetooth even in the background.
5. Pick the right vehicle model/year.
6. Settings → ELM327 Identification: all TRUE = adapter OK; a FALSE on the Module row points to a key-not-in-RUN, dirty OBD pins (6 & 14), or a bad adapter.
7. VIN won't read? Wait a few seconds, check the socket pins, or set Settings → Alternative VIN Source (try PCM/TCM/ABS/BCM).
8. Fully restart the app (not just background).

• Option not listed: configuration is read live — if it isn't shown, your module doesn't support it.
• Value rejected or ABS/CEL appears: the value is out of the module's accepted range — choose one within range.
• Changed but no effect: the vehicle may override the setting (often safety-related) — nothing can be done.
• Procedure failed: confirm the exact sequence, correct any wrong value, and retry; ensure a valid license for that VIN.

• NAG1 transmission reset — the KK 3.7 uses the 42RLE 4-speed, not the NAG1.
• Adaptive Cruise Control calibration — the KK isn't equipped with ACC.
• DPF regeneration — that's diesel-only; your 3.7 is gasoline.