TECHNICAL SERVICE OPERATIONS

MAS004868 DS 25-28
Diagnostic Sheet
FROM: Maserati TSO
TO: Maserati Network

HVAC DIAGNOSTIC WORKSHEET

IMPORTANT NOTICE This bulletin supersedes MAS004757 DS 25-16 released on May 30, 2025. It contains
updated information, please ensure all previous versions are discarded.

DATE: SEPTEMBER 05, 2025

This Diagnostic Sheet serves as a guide and provides a diagnostic path to help determine the root
cause of certain HVAC concerns. This Diagnostic Sheet requires a BOL to be submitted.

MODELS: Grecale, GT/GC, MC20 (All MY)
WHEN DEALING WITH HVAC CONCERNS SUCH AS “AC NOT BLOWING COLD,” DO NOT ASSUME IT IS DUE
TO LOW REFRIGERANT. DO NOT EVAC AND RECHARGE THE HVAC SYSTEM UNTIL ADVISED TO DO SO BY
THE BOL TEAM!

Perform and complete the inspection procedures starting on the next page. Once completed. Open a
BOL “Support Request”, report all results, and attach pages 2 and 3 along with all EVO reports.
If any of the below information is missing, Maserati reserves the right to request it before
providing support/approval or feedback to Blue On Line. Maserati reserves the right to deny
coverage for repairs not performed to factory standards. For additional questions or support,
please contact Maserati Technical Service Operations.

© 2025 Maserati North
America. Aftersales
www.maseratiusa.com

MAS004868

All rights reserved. Reproduction or translation in
whole or in part is not permitted without
authorization from the publisher. Printed in USA

Page 1 of 3

A) General HVAC Pre-diagnostic Inspections
1. Perform a walk-around visual inspection of the vehicle exterior for damage, especially the
front bumper and grill for condenser damage, and the driver-side mirror where the ambient
sensor is located.
2. Perform a visual inspection of the engine bay, air vents, and Cabin Filter. Check the outside
recirc vents for debris. Inspect the accessory belt, AC compressor, all related lines, and fittings
for issues.

TECHNICAL SERVICE OPERATIONS

DIAGNOSTIC PROCEDURES

B) HVAC STATIC and DYNAMIC performance inspections
1. Run the engine at IDLE until fully warmed up. While the engine is running, create a DTC and Parameter
report in PDF format of the following modules: ECC, ECM, BCM, ICS, and (ICS-R if equipped).

STATIC PERFORMANCE INSPECTION
This test is essential for evaluating the resting (static) pressures of the A/C system and provides a
baseline for diagnosing potential refrigerant-related issues.
1. What is Shop Ambient Temp during the test above?_______________________
2. What is Shop Ambient Humidity during the test above?_____________________
3. With the engine OFF for a minimum of 15 minutes (To allow pressures to equalize), hook up
your HVAC manual gauges and document LOW and HIGH side pressures (Take a picture of
gauges (High and Low) and attach it to BOL and Label “ENGINE OFF – PRESSURES”)
DYNAMIC PERFORMANCE INSPECTION
This test is essential for evaluating real-time system performance under load, ensuring that the
air conditioning system is functioning within manufacturer specifications.
The following tests must be performed with all doors closed and windows rolled up.

1. Start the vehicle up and let the engine run at IDLE, then set the HVAC to the following:
a.
b.
c.
d.
e.

AC: MAX ON
MODE: Center Dash Vents
Blower: MAX
TEMP: LOW (Dr. and Pass. sides)
AUTO: OFF

© 2025 Maserati North
America. Aftersales
www.maseratiusa.com

MAS004868

All rights reserved. Reproduction or translation in
whole or in part is not permitted without
authorization from the publisher. Printed in USA

Page 2 of 3

3. Place a DIGITAL Temp Gauge in the Dash Center Vent(s) and document the LH Temp. (Driver’s
Side) and RH Temp (passenger side).
4. Take photos of HVAC pressure gauges (High and Low) attach them to BOL and Label them
“ENGINE RUNNING – PRESSURES”
a. DYNAMIC (IDLE) LOW PRESSURE READING __________BAR
b. DYNAMIC (IDLE) HIGH PRESSURE READING __________BAR

5. Measure the air temperature from the front-facing vents using a digital thermometer. Set the
HVAC TEMP to LOW with the fan speed on HIGH. Air distribution to front-facing vents. Attach
a picture of the MIA of the front dash and A/C controls.
6. Attach another picture of the A/C machine with the engine fully warmed up and running with
engine speed at 2500RPM Hold the engine there for 5 minutes then take a picture. Also,
perform and attach another full vehicle report during this time so we can see and monitor
parameter values. Attach the report to the BOL.
a. DYNAMIC (2500 RPM) LOW PRESSURE READING __________BAR
b. DYNAMIC (2500 RPM) HIGH PRESSURE READING __________BAR

TRI-ZONE SYSTEM (Optional on some vehicles)
If the customer has concerns regarding this system, check the ICS-R for DTCs along with
performing the same diagnosis.

© 2025 Maserati North
America. Aftersales
www.maseratiusa.com

MAS004868

All rights reserved. Reproduction or translation in
whole or in part is not permitted without
authorization from the publisher. Printed in USA

Page 3 of 3

TECHNICAL SERVICE OPERATIONS

2. Wait 5 minutes and then use the EVO to run a report of the BCM, ECM, and ECC modules.
PARAMETERS & DTCS and SAVE as PDF then Attach to BOL.