Jaguar Security Module – Troubleshooting Guide

Use this guide only after your Security / Locking Module (SLM) has been rebuilt and reinstalled.

A. Symptoms covered

• Brake lights inoperative or stuck ON

• Security / central locking not working or intermittent

• Alarm not arming or disarming correctly

1. Basic checks (applies to all symptoms)

• Verify battery voltage is 12.4V or higher with ignition off

• Check all relevant fuses for the security/locking system and brake lights

• Inspect SLM connector for bent pins, corrosion, or loose fit

• Confirm the SLM is fully seated and all ground points near it are clean/tight

2. If brake lights do NOT work at all

• Check all rear brake-light bulbs for open filaments or wrong type installed

• Inspect bulb sockets for heat damage, melted plastic, or green corrosion

• Check grounds at rear lamp assemblies for rust, loose screws, or broken wires

• Inspect wiring in the trunk/boot hinge area for broken or pinched wires

• Test brake-pedal switch operation

  • Confirm power and ground at the switch

  • Verify the switch output changes when pressing and releasing the pedal

• If the brake-pedal switch does not send a clean signal, repair or replace it first

At the SLM (professional/technician check)

• Confirm the SLM has proper power and ground feeds

• Confirm the brake-pedal signal is reaching the SLM input

• Check for brake-lamp output leaving the SLM when the pedal is pressed

  • If input is good but there is no brake-lamp output, the SLM is suspect

  • If output is present but the brake lights still do not work, the fault is in wiring, grounds, bulbs, or lamp assemblies, not the SLM

3. If brake lights are STUCK ON

• Confirm brake-pedal switch is correctly adjusted and not physically stuck

• Unplug the brake-pedal switch

  • If the lights go out, replace/adjust the switch or its bracket

  • If the lights stay on with the switch unplugged, check for shorted wiring to the lamps

• Inspect harness near trunk/boot hinge and rear lamps for melted or pinched wires

• If wiring and switch test good but brake outputs stay powered leaving the SLM, the SLM may be at fault

4. If security / central locking still has issues

• Verify key fob battery condition and re-sync if required

• Check door-lock fuses and any separate relays related to central locking

• Inspect door-lock actuators and linkages for sticking or mechanical binding

• If only one or two doors fail to lock/unlock, suspect local actuators or wiring in that door

• If all doors fail together and power/grounds at the SLM are correct, SLM or vehicle wiring/control signals may be at fault

5. When to re-contact UpFix

• You have verified:

  • All fuses, bulbs, sockets, and grounds are good

  • Trunk/boot harness and rear lamp wiring are not damaged

  • Brake-pedal switch works and its signal reaches the SLM

  • The SLM has proper power and ground

• And you still see:

  • No brake-lamp output leaving the SLM when input is good

  • Brake-lamp output stuck ON with a good switch and good wiring

  • System-wide locking/security failure with correct power/grounds and no wiring faults

When you contact us, please include:

• Vehicle year, model, and VIN

• A list of any fault codes pulled from the vehicle

• Test results for power, ground, and brake-switch signal at the SLM connector