B1402 on 2012-2013 Jaguar XF: Causes for Dual Battery Fuse Box Faults

What's Unique About the 2012-2013 Jaguar XF

What's unique to this Jaguar platform is a well-documented software issue. The vehicle's Gateway Module (GWM) is known to falsely report this B1402 fault when no actual hardware problem exists. Before assuming a component has failed, it's critical to check for this software glitch, as a simple module update often resolves the issue completely. This issue is also documented for the Jaguar XJ on the same platform.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Eco Start-Stop system is inhibited or non-functional.
🎬 Watch: A quick guide to fixing common Eco Start-Stop issues.
• Battery charge warning light is illuminated on the instrument cluster.
• 'Eco stop inhibited' message displayed.
• Instrument cluster lights may flicker during an attempted eco-start.
• Un-commanded shutdown after an ECO Stop event, requiring an ignition restart (as noted in SSM72087).

Most Likely Causes

1. Gateway Module (GWM) Software Glitch 🔴 High Probability Jaguar issued a Technical Service Bulletin (JTB00310NAS3) specifically for this issue, where the GWM falsely flags the B1402-96 code. This is the most common root cause.
   How to confirm: A Jaguar dealer or specialist with the SDD diagnostic tool can check the current software version of the GWM and see if the update applies. The TSB is applicable to 2012-2013 XF models in VIN range S20753-U03286.
   Typical fix: Reconfigure the existing Gateway Module with updated software using the Jaguar SDD tool. No parts are required. The labor for this software flash typically takes about one hour.
   Est. part cost: $0
2. Loose or Corroded Main Battery Ground Cable 🟡 Medium Probability → Shop Vehicle Battery According to service document SSM71917, the main negative ground cable can work itself loose where it connects to the vehicle body at stud G4D178, causing a range of electrical faults, including B1402.
   How to confirm: Visually inspect the main negative battery cable's connection to the chassis in the trunk, on the right side. Check if the connection is loose, dirty, or corroded.
   Typical fix: Disconnect the ground, clean the stud (G4D178), the cable eyelet, and the body contact area thoroughly. Re-secure the connection and torque it to the specified 13.5Nm.
   Est. part cost: $0
3. Faulty Dual Battery Fuse Box (DBFB) / Junction Box (DBJB) ⚪ Low Probability → Shop Vehicle Battery While less common than software or grounding issues, the internal contactor relay within the fuse box can fail. This should only be suspected after the software and ground issues are ruled out.
   How to confirm: After ruling out software and grounding, a technician can use a high-end scan tool to command the contactor on and off to test its function. Listening for 4 audible clicks from the DBFB within 40-60 seconds of starting the vehicle can also indicate a successful self-test.
   Typical fix: Replace the Dual Battery Fuse Box/Junction Box. The OEM part number is C2Z23250.
   Est. part cost: $150-$300

Rare But Worth Checking

• Wiring Harness or Connector Issue: A fault in the wiring between the Gateway Module and the Dual Battery Fuse Box can trigger this code. This could be due to chafing, corrosion, or a loose pin in a connector. Document SSM72087 advises checking the integrity of these circuits if other causes are ruled out.
• Incorrectly Connected Power Cables: If major electrical work was recently performed, it's possible the generator and starter cables were transposed (swapped). This is a rare scenario but is mentioned as a diagnostic step in service document SSM72087.

Diagnosis Steps

1. Connect a Jaguar-approved battery support unit to maintain stable voltage.
2. Scan the vehicle for all Diagnostic Trouble Codes (DTCs) using a compatible scan tool (Jaguar SDD preferred).
3. If B1402-96 is present on a 2012-2013 XF (VIN S20753-U03286), check for TSB JTB00310NAS3. If applicable, update/reconfigure the Gateway Module (GWM) using the Jaguar SDD tool.
4. Clear codes and perform a drive cycle to see if the fault returns. If it does not, the repair is complete.
5. If the code returns or the software is already up-to-date, inspect the main battery negative ground cable connection to the chassis (stud G4D178). Ensure it is clean, tight, and torqued to 13.5Nm as per SSM71917.
6. Inspect the wiring and connectors between the GWM, Dual Battery Module, and the Dual Battery Fuse Box for any signs of damage, corrosion, or loose connections, including the LIN Bus circuit.
7. If all wiring and grounds are good, the fault likely lies with the Dual Battery Fuse Box itself. Test its function with a scan tool or listen for the self-test clicks (4 audible clicks within a minute of startup).
8. Replace the Dual Battery Fuse Box (Part No. C2Z23250) if it is confirmed to be faulty.

Parts You'll Likely Need

• Dual Battery Fuse Box / Junction Box (OEM #C2Z23250) — This part is only needed if the internal contactor relay has failed, and after software and grounding issues have been ruled out. It contains the contactors that trigger the B1402/B1403 codes.
  Trusted brands: Jaguar (OEM)
  OEM price range: $200-$300
  Aftermarket price range: $150-$250

Related Codes That Often Appear With This One

• B1403-96 — This code refers to 'Dual Battery Fuse Box - Contactor 2'. Since both contactors are in the same assembly and controlled by similar logic, a systemic issue like a bad ground or software glitch can cause both codes to appear together.

Technical Service Bulletins (TSBs) & Recalls

• JTB00310NAS3: GateWay Module DTC B1402-96 Causing ECO Stop Inhibited Or Battery Charge Warning Messages While Driving.
• SSM71917: XF vehicles with battery charging warning lamp illuminated - 2012 Onwards.
• SSM72087: XF/XJ Eco Stop/Start Additional Diagnostics Information.

Platform-Specific Known Issues

• A known software bug in the Gateway Module can cause this code to be set erroneously, with the official fix being a software update per TSB JTB00310NAS3.
• The main battery ground connection to the body (stud G4D178) is a known weak point that can become loose, leading to this and other electrical fault codes (SSM71917).

Mechanic-Grade Diagnostic Values

• Main battery negative ground cable stud torque — expected: 13.5Nm. Failure: A loose stud can cause intermittent and high-resistance connections.
• Ground point voltage drop test — expected: Under 0.5V (500mV). Failure: A reading higher than 0.5V while the circuit is under load (e.g., cranking the engine) indicates a poor ground connection that needs to be cleaned or repaired.

Hidden / Shadow Codes Worth Checking

• B1402-96: The '-96' suffix is a Failure Type Byte (FTB) indicating a 'Component Internal Failure'. This tells the technician that the module reporting the code believes the component itself has an internal fault, as opposed to a circuit issue like an open or short. (see via This is typically displayed on professional scan tools like the Jaguar SDD system.)

Scan Tool Commands That Help

• Jaguar SDD (Symptom Driven Diagnostics): Configure existing module - Gateway module — This is the specific service function required to apply the software update that fixes the false B1402-96 code, as detailed in TSB JTB00310NAS3.
• Jaguar SDD (Symptom Driven Diagnostics): Battery replacement / Battery Monitoring System Reset — This function must be run after replacing the main or secondary battery to recalibrate the Battery Monitoring System (BMS). Failing to do so can lead to incorrect charging and other electrical faults.
• Jaguar SDD (Symptom Driven Diagnostics): Dual battery system diagnostic service routine — This is a guided diagnostic test to check the functionality of the dual battery system components after initial checks (software, grounds) have been performed.

Wiring & Ground Locations

• G4D178 — Right side of the luggage compartment. This is the main negative battery cable's connection point to the vehicle body.. This is a known weak point for becoming loose or corroded, directly causing B1402 and other electrical faults by creating an unstable ground for the entire battery management system.
• Gateway Module (GWM) — At the rear of the right wheel arch in the luggage compartment, adjacent to the Dual Battery Module (DBM).. The GWM is the control module that hosts the software for the dual battery system and is the source of the false B1402 code. The software update is performed on this module.
• Dual Battery Junction Box (DBJB) / Fuse Box (DBFB) — Adjacent to the primary battery in the luggage compartment.. This box contains Contactor 1, the physical component that the B1402 code refers to. A failure of this part is the ultimate hardware cause if software and grounds are good.
• Dual Battery Module (DBM) — At the rear of the right wheel arch in the luggage compartment, adjacent to the GWM.. The DBM receives signals from the GWM via a LIN bus connection and directly controls the contactors in the DBJB. A fault in this module or its wiring could also trigger the code.

OEM Part Supersession History

• C2Z17854 → C2Z23250 — Part revision or supplier change.
  Heads up: C2Z23250 is the correct replacement for the earlier part number.

Model Year Variations Within This Range

• 2012-2013: The software glitch causing false B1402-96 codes is specific to XF models in the VIN range S20753-U03286, as defined by TSB JTB00310NAS3. Vehicles outside this range may have the code but the software update would not be the prescribed first step.