Possible causes of no-start with push button keyless systems:
In no particular order, we’ve listed some of the many possible causes of a no-start condition on a push button keyless system:
• Driver not pushing the button in far enough.
• Defective push button (or fault in push button wiring harness).
• Driver not depressing the brake pedal (automatic) or clutch pedal (manual).
• Defective brake or clutch pedal position switch (or fault in the switch wiring harness).
• Transmission not in Park (or Neutral).
• Defective Park/Neutral safety switch.
• Driver does not have the smart fob with them (forgot it), or has wrong fob for the car (if they own several cars with push button start systems).
• Smart fob has a problem (defective transponder, low or dead battery, or fob code is out of sync or is corrupted). You may see an error message that says, “fob not recognized.” Check/replace the fob battery first to see if that cures problem. If not, the fob may need to be reprogrammed or replaced.
• Vehicle antenna(s) does not recognize the smart fob (wiring problem or defective keyless antenna control module). You may get an error message that says, “fob not recognized.” Check signal strength with scan tool.
• Defective steering interlock release module.
• CAN bus communication fault (should set a “U” diagnostic trouble code).
• If the engine does not crank when the button is depressed, it could be a conventional electrical problem such as a dead car battery, bad starter relay or solenoid, bad starter or a fault in the starter circuit wiring harness.
• If the engine cranks but does not start, and the anti-theft light is not flashing, the fault is not likely in the push button start system. Check for fuel problems (bad fuel pump, fuel pump relay, plugged fuel filter, no gas in tank), ignition problems (like a bad crank sensor or ignition control module), or a mechanical problem (broken timing belt or broken teeth on flywheel).
DIAGNOSIS
On most of these systems, the best and fastest way to get to the core of a no-start problem is to use a factory scan tool (or an aftermarket scan tool that has similar software capabilities) to run whichever self-tests are available for the keyless start system.
On Nissans, for example, the Nissan Signal Tech II scan tool (which can also be used for the Tire Pressure Monitoring System) includes menu options for checking the intelligent key system relative signal strength, for testing the remote keyless entry relative signal strength and for checking the strength of the output signal from the vehicle keyless antenna. If an intelligent key fob or steering column lock is defective and has to be replaced, the IDs of the parts must be registered and programmed into the system — which is a dealer-only job that requires the factory Consult-III scan tool.
It’s the same story with other import makes. If you discover a defective smart fob, replacing it requires the same programming procedures as replacing or duplicating a key with an anti-theft chip. You’ll need a new car dealer or certified locksmith to do the programming.
Something else to keep in mind: if repairs require disconnecting the battery to replace an electronic component, make sure you have the factory radio and navigation system codes before you disconnect the battery so these devices can be reset afterward. Other on-board electronics may also require a relearn or reset procedure following a battery disconnect. Refer to the vehicle service literature to see what may be affected, and what’s required to get these systems operating again following a battery disconnect.
