Ignition does not turn on
Make sure the key is correctly inserted into the start control box (SCU), and that the key matches the car (if the key is not programmed or from another vehicle, the SCU will push it out). If the vehicle is equipped with an automatic transmission, the parking mode must be engaged (P), and if the gearbox is manual, the neutral gear must be engaged.
Check that the circuit between the start button and the central fuse box (CJB) no open or short to ground.
Check that the CAN network is working, i.e. there is no break or short circuit in it. Otherwise, CJB, ECM and Dashboard will not be able to communicate. Check these modules for relevant DTCs and refer to the appropriate DTC Index.
The engine will not start
The immobilizer status LED is displayed in the lower left corner of the instrument panel. When the key is inserted into the SCU, the LED will turn on for 3 seconds and then turn off. If the car is protected by an immobilizer (remote control failed test), LED flashes slowly (once every 2 seconds). In addition, using the diagnostic system, it is necessary to check the diagnostic trouble codes (DTC), related to CJB, instrument panel, ECM and ABS module.
One possible cause of starting problems on an automatic transmission vehicle is the switch being locked in the park position.
Verify that there is no short or open in the engine start request circuit between the CJB and the ECM.
Check the starter relay circuit.
Check that the steering column lock (SCL) is functioning correctly. When the key is inserted into the slot, the SCL should disengage and the steering wheel should turn freely.
Check that the CAN network is working, i.e. there is no break or short circuit in it. Otherwise, the CJB, instrument panel, ECM or ABS module will not be able to communicate and the modules will not request to unlock the immobilizer.
On vehicles with automatic transmission, also check the CAN network between the CJB and the transmission control unit (TCM). CJB before issuing permission to start the engine uses a signal "LockedInP" from the TCM to determine if the transmission is in position. CJB uses format values 0x01; if the CJB finds a value less than the specified value, no launch permission is granted and the key is not popped from the SCU.
In the case of a manual transmission, the clutch pedal must be depressed; check CAN network between CJB and ECM to make sure the clutch pedal is depressed (ClutchPedalSwitch75pct = TRUE and ClutchPedalPressed2 = True). Before receiving these signals, it is impossible to start the car.
On vehicles with automatic transmission, check the CAN network between the ABS module and the CJB. CJB uses signal "BrakePedalActive" to check if the brake pedal is depressed when the engine start authorization is issued. CJB uses the value = TRUE. If the CJB does not receive this signal, permission to start the engine will not be given.
Engine cranks but won't start
If the engine crankshaft rotates, the EMS has passed the test required by the CJB. If the test result is negative, the ECM will not energize the starter relay. This can be checked by looking at the LED on the left side of the instrument panel, which should illuminate for 3 seconds when the key is inserted, or by reading DTCs related to the CJB or ECM.
In all cases of problems with starting the engine, the most obvious causes of the malfunction should first be ruled out:
1. Check the power and grounding of all required modules.
2. Check other systems/functions for unusual behavior/operation.
3. Check the functions that operate abnormally.
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