Every Gladiator JT since 2020 has a standard OBD2 port under the driver's side dash. A $25 Bluetooth scanner and your phone will read most codes; a professional-grade tool adds live data, bi-directional tests, and Stellantis-specific subsystems.
OBD2 scanning is the first step in diagnosing any check engine, stability control, or four-wheel-drive warning light. Before paying a shop's diagnostic fee, pull the code yourself — most common faults are identifiable from the code number and a bit of research.
**Port location:** The OBD2 port on the JT is under the driver's side dash, to the left of the steering column, facing down. It's a standard 16-pin trapezoid connector.
**What a basic scanner reads:** Generic P-codes (powertrain), B-codes (body), C-codes (chassis). These are standardized across all vehicles and any $25 scanner reads them.
**What a professional scanner reads in addition:** Manufacturer-specific codes (U-codes for network faults, proprietary Stellantis codes), live sensor data, freeze frame data, bi-directional actuator tests (can command the throttle body open, fire individual injectors, test ABS modulators). The BlueDriver Pro and Autel MX808 bridge the gap between consumer and professional.
1. Plug the scanner into the OBD2 port with the ignition off.
2. For Bluetooth scanners: pair the scanner to your phone and open the companion app. For standalone scanners: turn the ignition to ON (not cranked) and the scanner powers up.
3. Select "Read Codes" or "Diagnostic Scan." The JT's ECM communicates over CAN bus — most scanners connect within 10–15 seconds.
4. Record all stored codes, pending codes, and freeze frame data. A pending code hasn't triggered the check engine light yet but has detected a fault. Don't ignore pending codes.
5. Look up each code using the scanner's database, the BlueDriver app's integrated repair reports, or an online resource like OBD2Pros.com.
**P0128** — Thermostat performance (coolant not reaching operating temperature fast enough). Common on the Pentastar with a failing thermostat, especially after 60,000 miles. Thermostat replacement is a 1–2 hour DIY job.
**P0300/P0301–P0306** — Misfire detected (P0300 random, P030X cylinder specific). Often coil pack failure on the Pentastar — common after 60–80K miles. Individual coil packs run $25–45 and swap in 15 minutes.
**P0456** — Small evap leak. Frequently a loose or cracked gas cap. Check and tighten the gas cap first. If the code returns, an evap smoke test is needed to locate the leak.
**P0087** — Fuel system too lean / low fuel pressure. Could be a clogged fuel filter-pump module or weak pump. Check fuel pressure at the rail before condemning the pump.
**C1431 / C1432** — ABS wheel speed sensor codes. The JT's wheel speed sensors live at each hub — trail use with mud and debris is hard on them. Inspect the sensor harness and connector for damage before replacing the sensor.
**U0100** — Lost communication with ECM. Often a transient fault from a dead battery, jump start, or module reset. If it recurs consistently, investigate the CAN bus network.
Clearing a code doesn't fix the problem — it resets the fault counter and turns off the check engine light. If the fault condition is still present, the code will return within 1–3 drive cycles. Clear codes only after you've addressed the root cause.
To clear: select "Clear Codes" in your scanner app. The scanner sends a reset command to the ECM. All stored faults, pending codes, and readiness monitors reset.
**Emissions testing note:** After clearing codes, readiness monitors take several drive cycles to complete. If the JT's emissions test is coming up, don't clear codes right before — you'll likely fail for incomplete monitors even without an active fault.
Veepeak mini Bluetooth OBD2: ~$25. Reads standard P/B/C codes, connects to Torque Pro or OBD Fusion apps. Good for a first scanner.
OBDLink MX+: ~$100. Faster, more reliable Bluetooth, compatible with most professional apps. The step up for owners who want live data and serious diagnostics.
BlueDriver Pro: ~$120. The integrated repair reports (showing verified fixes from other users with the same code on the same vehicle) are genuinely useful and set it apart from generic scanners.
Autel MaxiCheck MX808: ~$189. Full bi-directional control, oil reset, ABS bleeding, and deeper Stellantis coverage. Worth it for DIYers who work on multiple vehicles or want near-professional capability.
| Part | Vendor | Est. price |
|---|---|---|
| BlueDriver Pro Bluetooth OBD2 Scanner (iOS/Android) | BlueDriver | ~$120 |
| Autel MaxiCheck MX808 Scan Tool | Autel | ~$189 |
| Veepeak OBD2 Bluetooth Scanner (budget) | Veepeak | ~$25 |
| OBDLink MX+ Bluetooth Scanner | OBDLink | ~$100 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.