Land Rover Passive Entry Passive Start

David Technical Support Specialist Commack, New York Posted   Latest  

Beginning in MY 2010 Jaguar and Land Rover began using a new keyless start “Passive Entry Passive Start (PEPS)” system which has been problematic. The Keyless Vehicle Modules from … have a very high failure rate, especially if they have to be programmed with new keys. New keys cost about $400 and a new KVM costs around $200, add programming and R&R labor and you’re getting close to a grand just to add a key. Because the dealers charge so much for a new key, a lot of people want to try used keys or ebay keys. These keys cannot be used and will not program.

In general, when the driver presses the Engine Start button the Central Junction Box sends a message to the KVM to wake up. The KVM wakes up and sends a wireless signal to the key using the low frequency antennas installed around the car. If the key is within 1 meter, it picks up the signal and sends a response with a pass code to the high frequency antenna in the rear of the vehicle. The KVM checks the pass code and then sends it to the CJB. The CJB checks the pass code and enables the fuel pump and the electrical power distribution. When the Engine Start button is pressed and held the CJB reads it, verifies the brake and park/neutral status, and sends a start request to the engine module. The engine module actuates the starter relay.

If the engine cranks but doesn’t start, it is not an immobilizer problem. Immobilizer problems are commonly caused by bad keys, bad KVMs, low battery voltage, and CAN faults. 

These vehicles are extremely sensitive to low battery voltage, Jaguar wants you to have at least 12.4 volts. Extremely low voltage can cause the battery monitor system to cut power to the keyless vehicle module which disables keyless start. Excessive voltage drop while cranking can cause modules to lose immobilizer configuration. Just having the ignition on drains the battery very quickly, it’s a good idea to hook up a charger / power supply when scanning and diagnosing the vehicle. 

Begin testing with the battery, if it is 4 or more years old, has acid leakage, is too small for the vehicle, or is a cheap / unreliable brand, replace it. Next check the voltage; use a test light or headlights for 15-30 seconds to bleed any surface charge off, if it is less than 12.6 volts charge the battery until the rate falls below 1-2 amps. Put the negative clamp of the charger on the body, engine, or chassis, not the battery negative terminal. This way the battery sensor will register that the battery is being charged. If a conductance tester fails the battery, replace it. Even if it passes a conductance test, do a carbon pile load test. Load the battery to 1/2 its CCA for 15 seconds, if the battery can’t stay above 9.5 volts, it needs to be replaced. Any time the battery is disconnected reset the battery data and the immobilizer. It’s also a good practice to verify that there are no parasitic drain problems and that the charging system is working as well.

If there is a problem with the key not being recognized or the door was opened with the mechanical blade, the cluster will usually display “Smart Key Not Found” when trying to start. The cluster lights will not come on, but the vehicle can still be woken up by pressing the Start/Stop button. The information display part of the cluster should then come alive with a message / odometer reading. 

Put a fresh CR2032 battery into the key and try starting again. Look in the owner’s manual for the emergency start procedure which bypasses the Keyless Vehicle Module. The XF has a “Starter Control Unit” in the lower left of the dash where the key is inserted. On most other vehicles the emergency procedure has you put the key in a special place with an antenna, like under the steering column or on the shifter surround. The car will try to manually detect and read the key, and if it works the engine will start.

If the emergency start procedure fails the immobilizer data may have been lost, hook up the Autologic and go to Security and Keys, then do an Immobilization Reset. Sometimes that’s all that is needed. Run a quick test and look for CAN communication faults, low voltage faults, and immobilization faults. The KVM is also known on some vehicles as the Remote Function Actuator (RFA). The Autologic should communicate to the vehicle on both the high speed and medium speed networks even if the cluster lights won’t come on. Make sure you can talk to the KVM, CJB, ECM, Cluster and Driver’s Door modules. 

If you have a CAN communication problem you need to check voltage at the diagnostic connector on pins 6 and 14 for the high speed (drive) CAN network, and pins 3 and 11 for the medium speed (body) CAN. Voltages should add up to almost 5 and should be roughly 2.3 / 2.7. Disconnect the battery and check resistance across those pins. 6 and 14 should be 55-65 ohms, so should 3 and 11. If the resistance reads 120 ohms there is likely a break in the CAN network or one of the modules with a terminating resistor is bad. You will can look at the schematics to find out which modules have the terminating resistors.

Michael Owner/Technician
Cartersville, Georgia
Michael Default

Hi David, How do you discern if you have a key problem, KVM problem or CJB problem? The one that I had was a bad key. Fortunately they had another key. Mike

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David Technical Support Specialist
Commack, New York
David Default

HI Michael, excellent question, Usually the vehilce won't power up (cluster won't light up) and the message on the cluster says "Smart Key Not Found" . If you put the hazzard flashers on it wakes up the medium speed can bus so communication is now possible with the medium speed can bus. Whch is Acess to every module on the start authorization process except the Engine Control Module. See if you

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Michael Owner/Technician
Cartersville, Georgia
Michael Default

Thanks David. Excellent information!

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