Antitheft and Alarm Systems: Testing and Inspection
Inspection and Verification
Anti-theft - Passive
The best method to confirm the correct operation of the Passive Anti-Theft System (PATS) is to check the LED (located in the center of the instrument panel). The LED should illuminate solid for 3 seconds, when the ignition status is set to ON, and then extinguish. This validates all PATS functions (i.e. the key transponder matches a stored key code, the challenge/response sequence between the respective modules was successful resulting in the EMS being enabled).
Ignition fails to operate
Check that the smart key is located within the vehicle interior, and that it is the correct one for the vehicle. Insert the smart key into the start control unit (located in floor console cubby box), this is an alternative method to allow Ignition On/Engine Start.
Check that the start button circuit to the CJB is not open circuit or short circuit to power.
Check that the CAN network is not malfunctioning, i.e. open circuit or short circuit. This would mean that the remote keyless entry module, Central Junction Box (CJB) and instrument cluster would be unable to communicate.
Engine fails to crank
If a PATS fault is detected, the LED will flash for 60 seconds at 4Hz with a 50% duty cycle. At the end of this period, the LED will flash a 2 digit code; this code is repeated 10 times. The meaning of these fault codes along with the frequency of flashing is given in the accompanying table. As a general rule a fault code of 16 or less will cause the vehicle not to crank. Additionally, the manufacturer approved diagnostic system should be used to check the instrument cluster, CJB & ECM for Diagnostic Trouble Codes (DTCs).
One potential occurrence for failing to crank could be due to the 'Not In Park' switch (input to the CJB) or the P & N start switch (input to the ECM).
Check the Crank Request output from the CJB to ECM is not short circuit to ground or open circuit.
Check the Starter Relay circuit.
NOTE:
Due to Smart Start both sides of Relay Coil are switched directly from ECM (If conditions correct)
Check that the Steering Column Lock correctly operates and the steering wheel can turn freely.
Check that the CAN network is not malfunctioning, i.e. the CAN circuit is open or short circuit. This would mean that the instrument cluster and ECM would be unable to communicate resulting in no Challenge being performed to enable the ECM. This would be supported by LED Flash Code 24, see PATS Fault Code Table.
Also check the CAN network between the ABS module and the CJB. The CJB uses the CAN_BrakePressureTMC signal to determine if the brake pedal has been pressed in order to allow an engine crank. The CJB uses a value of 0x03, if the CJB sees a value less than this, it will not enable the Crank Request Output.
Engine cranks but will not start
If the Engine is cranking it means that the ECM has passed the authorization required with the Instrument Cluster. If this authorization failed, the ECM would not engage the starter relay. This could be confirmed by verifying the PATS LED prove out (illuminated solid for 3 seconds) or by reading DTCs from the instrument cluster and ECM.
In this case, the fuel pump circuit should be verified. The Fuel Pump Delivery Module (FPDM), which is supplied via the RJB (authentication required with the instrument cluster) and controlled by the ECM, supplies the fuel pump.
In all cases of suspected non-start issues, the most logical failure modes should be eliminated first. i.e.
- Check all relevant supplies and grounds to the relevant modules listed herein.
- Note any unusual behavior from other systems/functionality.
- Note any functions that are not operating as expected.
PATS Fault Codes
For the various PATS modes/faults listed in the table , the instrument cluster will store a DTC and indicate this to the customer during the detection period defined in the 'when logged' column, by illuminating the indicator as described for 60 seconds and then flashing the LED 10 times as appropriate. The indication will stop immediately the ignition status is set to OFF any time during the fault indication sequence. Up to 4 DTCs could be stored per key read sequence (1-10 read attempts). No DTCs will be stored until all retry attempts are complete. Only the highest priority fault code will be flashed.
To determine the fault code from the LED: The LED will flash initially ten times with 1.5 seconds between. The LED will remain OFF for 2.5 seconds then flash a number of times with 0.5 seconds between (the number of times the LED flashes represents the first digit of the code), the LED will remain OFF for 1.5 seconds then flash a number of times with 1.5 seconds between (the number of times the LED flashes represents the second digit of the code).
The PATS LED will be commanded on as shown under 'indication'. Normal PATS operations are complete within 400ms of the ignition switch transition from OFF to ON or START, worst case for ECM communication problems will be less than 2 seconds. If PATS is not complete during the 2 seconds the ECM will terminate PATS and await the next ignition ON or START event. PATS faults will be indicated via the LED as soon as possible and will terminate the LED prove out. At ignition OFF all previous flashing will cease and the perimeter anti-theft system will control the LED when the vehicle is locked and armed.
1 If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
2 If the cause is not visually evident, verify the symptom and refer to the manufacturer approved diagnostic system.