Diagnosis And Testing: Turbo

Courtesy of CHRYSLER GROUP, LLC

ESIM SWITCH MONITOR - STUCK CLOSED 

At ignition off, the state of the ESIM switch is evaluated. If the switch is open, a pass flag is set and PCM will complete power down. If the switch is closed, the PCM will wait a calibrated delay time and open the OBD Vent Valve  . This should vent the vacuum in the Fuel Tank to atmosphere. If the switch opens, a pass flag is set and the PCM will power down. If the PCM detects that the ESIM Switch is still closed after a calibrated time, an error is detected and a switch stuck closed failure is set at the next engine run cycle.

SMALL LEAK MONITOR 

This is an accumulative monitor and the data from each valid event is recorded and added to the previously recorded events. The PCM timer records the engine on/drive cycle and engine off time for each small leak monitor event. For an event to be valid the PCM must see;

1. An engine on/drive cycle for a minimum of 2-5 minutes.
   NOTE:

   The engine on timer will stop counting after a maximum of 26 minutes.

2. And, when the engine is shut down, an engine off timer starts. There is a 12 minute delay time in which the PCM will ignore ESIM Switch input. The engine off timer period will continue to count until one of these three conditions exist:
   • The engine is started without a switch closure during the event.
     NOTE:

     At the next key on cycle a determination is made as to whether the event was valid and the information is kept.

   • An ESIM Switch closed input is received after the 12 minute delay during the event.
     NOTE:

     If the switch closed input is received, the PCM records that the switch has closed and stores the engine shut down time.

   • After a maximum of 17.5 hours without an ESIM Switch closure during the event.

This monitor will increment  the accumulation fail timers  until both  have reached a calibrated threshold (Engine on - 100 minutes and Engine off - 70 hours). When the monitor records a valid switch closure (small leak passing event)  the fail timers are reset.

LEAK SIZE DETERMINATION:  If the PCM did not see an ESIM Switch closed signal during the previous ignition off cycle, the event was valid, and there is a cold start, an intrusive leak test is run to determine if a large leak is present. Immediately after start-up, while the engine is cold, the Purge Solenoid is opened to create vacuum in the evaporative system to a calibrated vacuum point that is beyond the ESIM Switch closing threshold. The pass/fail time will vary based on the total fuel volume at the time of the test. 

• If the switch does not close at all during purging, because of a switch that is stuck open or vacuum cannot be created below -250 Pa within a calibrated time, it is determined to be a general evaporative system failure (P0440) DTC  .
• If vacuum is created and the switch has closed, the PCM stops purging and monitors the switch closure time. If the switch opens before a calibrated time, a large leak is present. Two consecutive failure events will mature a fault (P0455) DTC. 
• If vacuum is created and the switch has closed, the PCM stops purging and monitors the switch closure time. If the switch stays closed longer than a calibrated period of time, it is determined that a large leak is not present and the Small Leak Monitor will continue to run until the accumulative monitor reaches its threshold. If no ESIM Switch closures were recorded during the entire accumulated timer,  it is determined that a small leak is present (P0456) DTC. 

PURGE FLOW DIAGNOSTIC 

Since the vacuum hoses between the Purge Solenoid, Intake Manifold and Ejector Tee cannot be checked during the small leak diagnostic the FTP Sensor is used to monitor the Evap System pressure change during purging to determine if the hoses are disconnected or restricted. The Purge Flow Monitor Diagnostic will only run if the Small Leak Monitor recorded a pass on the previous ignition off event and the test data was valid. The boost portion of the monitor will only run when there is a sustained stable boost condition and not when the vehicle is at wide open throttle. The PCM runs the Purge Flow Monitor once per drive cycle for both engine operating modes and both diagnostics will run during the drive cycle if the parameters allow regardless if the first diagnostic failed.

• When the Purge Flow Monitor begins to run, the normally closed OBD Vent Valve is briefly opened to vent the system to atmosphere. After the Purge Solenoid is energized the PCM monitors the FTP Sensor pressure delta to determine a pass/fail.
• If the diagnostic fails when the engine is running in naturally aspirated mode, the PCM will set the (P0441)  DTC.
• If the diagnostic fails when the engine is running in boost mode, the PCM will set the (P1CEA)  DTC.