AfterSales Diagnostic Sheet
MAS002832
(BOL 21-28)

From: Aftersales - TSO
To: Maserati Network
Auburn Hills, MI.
October 29, 2021

NOTE: The below in depth diagnostic procedures are to be used along with the procedures
listed in the Workshop Manuals if a more comprehensive diagnosis is required.

Evap high load purge diagnosis with pressure sensor
Issue: Engine Warning Light On
Models: M157/M156/M161 Gasoline engine equipped with Evap pressure sensor from MY21
Issue description: Engine light switches ON in Cluster, with no effect or symptoms affecting
the drivability.
Conditions: The Engine Warning Light may switch ON when running or at standstill.
Engine Temperature will not affect the symptom (warm or cold engine has no influence).
Possible Engine ECU errors:
DTC in ECM module:
DFC_TESPL -> P04F0 (EVAP System High Load Purge Line "A" Performance-)
DFC_PSSPEmax -> P0453 (EVAP System Pressure Sensor/Switch "B" Circuit High-)
DFC_PSSPEmin -> P0452 (EVAP System Pressure Sensor/Switch "B" Circuit Low-)
DFC_PSSPMAX -> P0451 (Plausibility check pressure signal venturi tube: High)
DFC_PSSPMIN -> P0451 (Plausibility check pressure signal venturi tube: Low)
All the above DTC’s are related to the new pressure sensor used by the ECM to monitor
the high load purge line from the purge valve to the ejector tee and to the right intercooler
(Figure 2, Figure 3). The new pressure sensor is located on the connection pipe from the
purge valve to ejector tee (Figure 4, Figure 5).

Troubleshooting:
1. Save a FIRST ECM scan report (Parameters + DTCs) using MD/MD EVO and attach
it to a BOL report.
2. Only for V8 engines- in order to understand if the purge valve connectors are
correctly fitted and connected to the correct purge valves (3 way purge valve and 2
way purge valve connectors could be switched – Figure 1, Figure 3, Figure 5) ,
perform the following electrical checks on wiring harness:

Figure 1: - High load purge line on V8 engine.

a. Check the integrity of the 3 way purge valve connector and related ECM
connector, make sure there is no oxidation and that pin tightness is secure.
b. Check the 3 way purge valve wiring harness integrity and the correct pin-out
(Figure 2): Ensure there are no short circuits to power supply or ground and it’s
securely plugged in. Perform these checks with the KIN in the OFF position,
disconnected battery power supply and disconnected connectors from the ECM
and sensor, in order to isolate the wiring.

Figure 3: 3 way purge valve.

Figure 2: 3 way purge valve wiring diagram.

c. Check the integrity of the 2 way purge valve connector and related ECM
connector, make sure there is no oxidation and that pin tightness is secure.
d. Check the 2 way purge valve wiring harness integrity and the correct pin-out
(Figure 4): Ensure there are no short circuits to power supply or ground and no
open circuits. Perform these checks with the KIN in the OFF position,
disconnected battery power supply and disconnected connectors from ECM and
sensor, in order to isolate the wiring.

Figure 5: 2 way purge valve.

Figure 4: 2 way purge valve wiring diagram.

3. Perform the following electrical checks on the wiring harness:
a. Check the integrity of the pressure sensor connector and related ECM
connector, make sure there is no oxidation and that pin tightness is secure.
b. Check the wiring harness integrity (Figure 6): Ensure there are no short circuits
to power supply or ground and no open circuits. Perform these checks with the
KIN in the OFF position, disconnected battery power supply and disconnected
connectors from ECM and sensor, in order to isolate the wiring.
c. Check at pin 1 (Figure 6) of the pressure sensor connector to ensure the power
supply of 5V is present, with the KIN in RUN position.

Figure 6: Fuel vapor pressure sensor on high load purge line.

Figure 7: - High load purge line on V8 engine.

Figure 8: - High load purge line on V6 Levante.

4. If there are issues at the previous steps, repair as necessary or proceed replacing
defective components and then go to next step.
5. Perform, on ECM module, active diagnosis “Canister purge valve 1” via MD/MD EVO
and check if the 3 way purge valve is working properly (opening and closing when
modifying the duty cycle) with the key on and the engine off.
6. Verify that all the components of the High load purge line system are properly
installed and connected (Figure 7, Figure 8). These include connection pipes (from
purge valve to manifold, to ejector tee and to the intercooler), make sure there are
no leaks or obstruction of all the system components.
7. Collect all the information and measurements requested and open a BOL as a
Support Request.

Figure 9: - High load purge line on V8 engine.

Figure 10: - High load purge line on V6 engine Levante.

If you have any questions, please contact the Technical Support Helpdesk.

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