Theory Of Operation
Some vehicles are equipped with a KIN (Keyless Ignition Node) and Radio Frequency Hub (RF Hub). The KIN uses a Keyless Go Start/Stop push button for cycling the ignition on/off. Other vehicles uses a standard ignition switch to send ignition switch position inputs to the Body Control Module (BCM) and the BCM reads key transponder for a valid ignition key instead of the RF HUB.
When the operator presses the Start/Stop Button on a KIN, the FOBIK is validated wirelessly by the RF Hub (Radio Frequency Hub Module). If the FOBIK is recognized as belonging to the vehicle and is inside the vehicle, the system allows the ignition state of the vehicle to be changed by the operator between the LOCK, ACCESSORY, RUN, and START ignition states.
LED Operation (KIN)
The LEDs in the IGNM and Start/Stop Button provide visual indication of the ignition system and button use to aid the driver. The Logic for LED control is implemented in the RF HUB. The Start/Stop Button contain four LEDs:
- OFF Indication
- ACC Indication (Accessory)
- ON Indication (On or Run)
- Ignition Switch Indicator (button backlight)
The LEDs indicate the vehicle ignition position and are driven by the CAN bus signals related to the ignition position. The Center LED (Ignition Switch Indicator) will blink if there is a related concern.
Ignition Switch Operation (Non-RF HUB Equipped)
The Ignition switch provides the ignition switch inputs to the BCM for Ignition switch status. These are some of the Ignition switch Inputs and Outputs:
- Fused B+ (constant B+ feed all the time to the ignition switch)
- Ignition RUN/ACCESSORY (voltage present in Run/Accessory Positions only)
- Ignition RUN (voltage present in the RUN Position Only)
- Ignition RUN/START (voltage present in the RUN/START positions only)
- Ignition START (voltage present in the START positions only)
Since there is no RF HUB on vehicles equipped with an Ignition Switch, the BCM will read the Key Transponder.
The RF HUB will log a DTC indicating an incorrect Ignition status value is present; in this state the ignition status is unknown. This will continue until the correct signal is received by the RF Hub.
EVIC Operation
The Keyless Go feature requires the vehicle to be equipped with an EVIC display for prompts and status information. The display messages are:
- Service Keyless System
- FOB Not Detected
- FOB Left Vehicle
- Not in Park
- Push Brake Pedal and Push Button to Start
- Push Clutch Pedal and Push Button to Start
- Vehicle not in Park Warning
BCM/RF Hub Module Interaction
There are a few things that must take place before the starter relay can apply voltage to the starter. Below are some key points to check when diagnosing a no crank condition.
The BCM requires two signals from the RF HUB to verify the ignition is in the run or start position. The voltage on the F20 circuit is one of these signals. It can be monitored in both the RF HUB and BCM data display screens as the Ignition Run/Start under the "Sensor" value. The run or start position voltage on this circuit should be at or close to Battery voltage.
Simultaneously the RF HUB busses the Ignition Run/Start status to the BCM. The BCM monitors the bussed input information as the secondary verification on the Ignition Run/Start status. The bussed messages can be monitored with the scan tool in both the RF HUB and BCM data display screens.
The F20 circuit voltage and the bussed ignition run/start status message received by the BCM must agree to enable starting. Once the vehicle is started, the loss of only one ignition signal will not cause the vehicle to cycle off as long as the other feed still indicates a "run status".
The RF HUB also requires an input from the Gated park switch (hardwired) and the OK to start CAN Bus message from the TCM (Crank Enable).
Diagnostic Aids
The No Crank Diagnostic serves as an aid in diagnosing the concern and is intended to be used as a general guide, since each no crank condition can be unique.
The No Crank Diagnostic Test assumes all of the following to be true:
- Communication to all configured modules in the vehicle is possible with the scan tool.
- The condition is currently present.
- The TCM, PCM, RF HUB, and BCM are at the latest calibration (part number) levels.
- There are no active DTCs.
- There are no applicable Recalls.
- There are no applicable TSBs.
- There are no PCM inhibits (i.e. RPM, Trans Range, Clutch).
- The FOBIKs complete function and operation is correct.
- All Battery cables and connections are clean and tight.
- There are no open fuses.
- The Battery is fully charged and can pass a load test from the GR8 tester.
- The engine rotates freely.
- Any aftermarket equipment/wiring that has been installed is operating correctly.
Starter Relay Operation
In a no crank condition the Starter Relay can be missing power or ground at pins 85 and 86, the 12 volt supply at pin 30, or output on pin 87. Further explanation of how a relay operates is listed below:
- Pin 30 is a constant B+ feed.
- The Starter Relay coil is supplied power from the BCM and a controlled ground from the PCM to pins 85 and 86 to energize the relay once the parameters for the Ignition Switch position and status, and all inhibit monitors (i.e. Clutch Switch, RPM, etc.) are satisfied.
While pins 85 and 86 are used to control the relay, which pin is supplied power and ground can vary between vehicles.
Refer to the specific wiring information for the vehicle being tested to properly test Starter Relay and circuitry.
- Pin 87 is an output circuit to the Starter Solenoid. Once the relay control circuit is energized, the coil winding in the relay magnetically pulls the internal switch closed. When the internal switch is closed the power at pin 30 is sent to pin 87 of the relay.