Case Number: S2418000010
Release Date: August 2024
Symptom/Vehicle Issue: MIL On/Check Engine Lamp On, Engine May Run Rough
Customer Complaint/Technician Observation: The customer’s complaint may
include the MIL on/ check engine lamp on. The condition may or may not include the
engine missing or running rough. Upon further investigation, the following DTC(s) may
be set in the Powertrain Control Module (PCM):
P0300-Multiple Cylinder Misfire
P0301-Cyl 1 Misfire
P0302-Cyl 2 Misfire
P0303-Cyl 3 Misfire
P0304-Cyl 4 Misfire
P0305-Cyl 5 Misfire
P0306-Cyl 6 Misfire

Discussion: This STAR On-Line is meant to pinpoint the diagnostic steps needed for
different types of misfires. If there are any other DTCs (P- codes) setting along with
the misfire DTCs, complete diagnostic checks on those FIRST in accordance with
Service Library procedure(s) before proceeding with the misfire DTCs. Failure to
do so could result in wasted diagnostic time and not fixing the problem.

This document does not authorize warranty repairs. This communication documents a record of past experiences. STAR Online
does not provide any conclusions about what is wrong with the vehicle. Rather, it captures all previous cases known that appear
to be similar or related to the vehicle symptom / condition. You are the expert, and you are responsible for deciding on the
appropriate course of action.

Contact STAR Center, or your Technical Assistance Center Via TechCONNECT or eCONTACT ticket if no
solution is found
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IF there are no other DTCs (P- codes) setting alongside the misfire DTCs,
proceed with the following:
BEFORE COMPLETING ANY WORK, COLLECT A FREEZE FRAME REPORT. IF
YOU ALREADY CLEARED THE DTCs, ATTEMPT TO DUPLICATE THE
CONDITION FIRST, THEN COLLECT FREEZE FRAME REPORT. THIS IS A
CRITICAL STEP!
Reviewing and understanding the data in the freeze frame data will provide
important information on what the conditions were when the DTC(s) were
setting.
If misfire DTC(s) cannot be duplicated, please refer to the information below for
diagnostic direction:
Diagnostic Direction
Misfire Diagnostic
Category

Applicable DTC

DTC Condition

DTC Status

Diagnostic Step

Single Cylinder

P0301, P0302, P0303,
P0304, P0305, P0306

ONLY 1 misfire code ACTIVE, STORED or Skip to Step 1.
present (not P0300) PENDING

Single Bank 1

P0300, P0301, P0302,
P0303

Any combination of
those 4 only

ACTIVE, STORED or Skip to Step 2.
PENDING

Single Bank 2

P0300, P0304, P0305,
P0306

Any combination of
those 4 only

ACTIVE, STORED or Skip to Step 2.
PENDING

All-Cylinder (across
banks)

P0300, P0301, P0302,
P0303, P0304, P0305,
P0306

All 6 individual cyl
ACTIVE, STORED or Skip to Step 3.
misfire codes must be PENDING
present (plus P0300)

Multi-Cylinder (across
banks)

P0300, P0301, P0302,
P0303, P0304, P0305,
P0306

-More than 1 misfire ACTIVE, STORED or Skip to Step 4.
code (not P0300)
PENDING
-Cannot be classified
as single bank

This document does not authorize warranty repairs. This communication documents a record of past experiences. STAR Online
does not provide any conclusions about what is wrong with the vehicle. Rather, it captures all previous cases known that appear
to be similar or related to the vehicle symptom / condition. You are the expert, and you are responsible for deciding on the
appropriate course of action.

Contact STAR Center, or your Technical Assistance Center Via TechCONNECT or eCONTACT ticket if no
solution is found
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After recording the above information, follow the procedure below for 3.0L SO (EFH):
1) For a single cylinder misfire: Follow the Service Library procedure fully in
specified order of diagnostic checks. Suggested to submit DIDI with evidence of
diagnostic checks to confirm warranty claim.
2) For a single bank 1/2 misfire:
a) Clear codes
b) Start vehicle
c) If codes return, remove downstream O2 sensor of associated misfire bank.
(Fig. 1 shows location of upstream and downstream o2 sensors.)

1 = Upstream
Bank 1
2 = Upstream
Bank 2
3 = Downstream
Bank 2
4 = Downstream
Bank 1

Fig. 1 O2 Sensor Locations

This document does not authorize warranty repairs. This communication documents a record of past experiences. STAR Online
does not provide any conclusions about what is wrong with the vehicle. Rather, it captures all previous cases known that appear
to be similar or related to the vehicle symptom / condition. You are the expert, and you are responsible for deciding on the
appropriate course of action.

Contact STAR Center, or your Technical Assistance Center Via TechCONNECT or eCONTACT ticket if no
solution is found
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d) Inspect catalytic converter internally through the upstream and downstream O2
sensor holes with borescope. Compare to pictures below to determine if it was
damaged. Images outlined in GREEN frames are OK (Figs. 2-4). Images in
RED frames are NOT OK (Figs 5-7).

Figs. 2-4 Good Catalyst Examples
This document does not authorize warranty repairs. This communication documents a record of past experiences. STAR Online
does not provide any conclusions about what is wrong with the vehicle. Rather, it captures all previous cases known that appear
to be similar or related to the vehicle symptom / condition. You are the expert, and you are responsible for deciding on the
appropriate course of action.

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Figs. 5-7 Bad Catalyst Examples
This document does not authorize warranty repairs. This communication documents a record of past experiences. STAR Online
does not provide any conclusions about what is wrong with the vehicle. Rather, it captures all previous cases known that appear
to be similar or related to the vehicle symptom / condition. You are the expert, and you are responsible for deciding on the
appropriate course of action.

Contact STAR Center, or your Technical Assistance Center Via TechCONNECT or eCONTACT ticket if no
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i) If no damage is found in catalytic converter, swap upstream O2 sensors (Fig.
1 – Sensors labeled 1 & 2). Clear codes. Start vehicle. Record Vehicle
Scan Report. If misfire DTCs return but switch banks, replace the upstream
O2 sensor that was originally in the bank associated with the original misfire
DTC in accordance with Service Library procedure. Suggest submitting DIDI
with evidence of diagnostic checks to confirm warranty claim.
ii) If damage is present in catalytic converter, replace part in accordance with
Service Library procedure. Suggest submitting DIDI with evidence of
diagnostic checks to confirm warranty claim.
NOTE: It is possible that a misfire can damage multiple components. After the
catalytic converter has been replaced, if misfire DTCs return or you have O2 sensor
related DTCs, also replace the associated O2 sensor in accordance with Service
Library procedure. Suggest submitting DIDI with evidence of diagnostic checks to
confirm warranty claim.
3) For all cylinder misfire (across banks):
a) Check battery voltage in accordance with the Service Library procedure.
i) If voltage results are below 10.5 V, follow the service procedure to diagnose
and repair the condition. Suggest submitting DIDI with evidence of diagnostic
checks to confirm warranty claim.
ii) If battery diagnostics are OK, proceed to next step 3b.
b) Follow SOL S2418000005 to inspect the air box, air filter, and air box lid for
proper assembly. The vehicle may have been recently serviced. If the airbox
assembly is not re-assembled correctly after an air filter check, it will disturb the
airflow across the Mass Airflow sensor (MAF) and cause varying levels of
symptoms.
i) If the air filter or air box lid is found not correctly assembled, follow the SOL
above to ensure proper installation. Make sure the repair has resolved the
condition.
ii) If those parts are found to be properly assembled, proceed to step 3c.
This document does not authorize warranty repairs. This communication documents a record of past experiences. STAR Online
does not provide any conclusions about what is wrong with the vehicle. Rather, it captures all previous cases known that appear
to be similar or related to the vehicle symptom / condition. You are the expert, and you are responsible for deciding on the
appropriate course of action.

Contact STAR Center, or your Technical Assistance Center Via TechCONNECT or eCONTACT ticket if no
solution is found
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c) Check supply side fuel pressure in accordance with Service Library procedure.
i) If an issue is found with supply side fuel pressure, follow the published repair
procedure in Service Library to resolve it. Suggest submitting DIDI with
evidence of diagnostic checks to confirm warranty claim.
ii) If no issues are found with supply side fuel pressure, proceed to step 3d.
d) Check for engine wiring harness for a rub-through or pinched wiring
condition. Pay close attention to the section of wiring that falls below or behind
AIS Y-Pipe near the lift stud (see Fig. 8 below).

Fig. 8 AIS Y-Pipe near the lift stud

i) If a wiring defect condition is found, replace or repair wiring harness in
accordance with Service Library procedure. Suggest submitting DIDI with
evidence of diagnostic checks to confirm warranty claim.
ii) If no wiring defect is found, proceed to next step 3e.
This document does not authorize warranty repairs. This communication documents a record of past experiences. STAR Online
does not provide any conclusions about what is wrong with the vehicle. Rather, it captures all previous cases known that appear
to be similar or related to the vehicle symptom / condition. You are the expert, and you are responsible for deciding on the
appropriate course of action.

Contact STAR Center, or your Technical Assistance Center Via TechCONNECT or eCONTACT ticket if no
solution is found
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e) Check the CAC Cold duct for proper connections/missing or damaged gaskets
(locations shown by red circles in Fig. 9).

Fig. 9 CAC Cold Duct Location on Engine Assembly

f) Check the Charge Air Cooler Duct connections proper connections/missing or
damaged gaskets (Figs. 10-11).

This document does not authorize warranty repairs. This communication documents a record of past experiences. STAR Online
does not provide any conclusions about what is wrong with the vehicle. Rather, it captures all previous cases known that appear
to be similar or related to the vehicle symptom / condition. You are the expert, and you are responsible for deciding on the
appropriate course of action.

Contact STAR Center, or your Technical Assistance Center Via TechCONNECT or eCONTACT ticket if no
solution is found
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Check for missing or damaged
gaskets at these connections.

Fig. 10 Charge Air Cooler Duct connections

No seal

Seal

Fig. 11 Missing Seal/Installed Seal
This document does not authorize warranty repairs. This communication documents a record of past experiences. STAR Online
does not provide any conclusions about what is wrong with the vehicle. Rather, it captures all previous cases known that appear
to be similar or related to the vehicle symptom / condition. You are the expert, and you are responsible for deciding on the
appropriate course of action.

Contact STAR Center, or your Technical Assistance Center Via TechCONNECT or eCONTACT ticket if no
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i) If missing gasket condition is found, repair condition in accordance with
Service Library procedure. Suggest submitting DIDI with evidence of
diagnostic checks to confirm warranty claim.
ii) If gasket is present, end diagnostic step.
4) For multi-cylinder misfire (mixed banks)
a) Determine if issue exists as Cold Start Multiple Cylinder Misfire Vs. Multiple
Cylinder Misfire under Other Conditions by reviewing freeze frame data.
i) Review the following freeze frame data parameters. If the values fall within
the given ranges, the issue is considered as Cold Start Misfire.
(1) Time To Start: Less than 60 seconds
(2) Engine Speed: 1200 – 1700 RPM
(3) Engine Coolant Temperature: Less than 125 F degrees
(4) Vehicle Speed: Less than 2 MPH
ii) If after reviewing freeze frame data, the conditions are found NOT to fall under
Cold Start Misfire as described above, follow normal diagnostic service
procedures as published in Service Library for the relevant misfire DTCs.
iii) If after reviewing freeze frame data, the conditions do fall under Cold Start
Misfire as described above, continue with the steps outlined below.
b) Cold soak the vehicle by letting it sit overnight for 8+ hours.
c) DO NOT START VEHICLE UNTIL THE FOLLOWING STEPS HAVE BEEN
COMPLETED. READ PROCEDURE TO THE END BEFORE PROCEEDING.
d) Following instructions found in the wiTECH Knowledge Base, set up a MicroPOD
(with trigger) to data record the vehicle. Use data recording template “T6 Cold
Start Misfire Template” that can be found under the “Flight Recordings” tab in
wiTECH.
e) Install the POD to the under dash OBD2 diagnostic port.
f) Make sure before starting the vehicle, the LED on the POD is in a green/steadyon state. If it is not, press the button on the trigger once. This will wake up the
POD and get it ready to record but will not trigger the recording yet. IF THE POD
LED IS ALREADY IN A GREEN/STEADY- ON STATE, DO NOT PRESS THE
TRIGGER BUTTON, THE POD IS ALREADY READY TO GO.
This document does not authorize warranty repairs. This communication documents a record of past experiences. STAR Online
does not provide any conclusions about what is wrong with the vehicle. Rather, it captures all previous cases known that appear
to be similar or related to the vehicle symptom / condition. You are the expert, and you are responsible for deciding on the
appropriate course of action.

Contact STAR Center, or your Technical Assistance Center Via TechCONNECT or eCONTACT ticket if no
solution is found
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Version 4.5 06/08/2022

g) When starting the vehicle, pay attention to whether you can feel the misfire
happening, or not, record details of your experience.
h) Start engine.
i) Wait 10 seconds after start-up then trigger flight recording.
j) Allow the vehicle to idle for 5 minutes without disturbing it.
k) After 5 minutes, depress the button on the POD trigger again to trigger a second
recording. Do not disturb the vehicle again for 5 minutes.
l) Attempt to get the answer to the following questions from the customer. We
understand some data may not be available, but please ask. The more data that
is available to review, the faster we can resolve the issue.
 Did the issue occur during a remote start?
 What were the conditions when the MIL came on (idle, driving)?
 What was the fuel level?
 What grade of fuel was used (Regular/Premium)?
 How long had the vehicle been sitting (minutes, hours, overnight)?
 Was the vehicle on an incline during start?
 Was the vehicle inside or outside?
 If outside, what was the weather?
 Please include all data in the STAR case (see step m)
m) Open a STAR case and attach flight recording files and any other recorded data
to STAR case (including details of symptoms experienced during diagnosis) and
await further instructions.

This document does not authorize warranty repairs. This communication documents a record of past experiences. STAR Online
does not provide any conclusions about what is wrong with the vehicle. Rather, it captures all previous cases known that appear
to be similar or related to the vehicle symptom / condition. You are the expert, and you are responsible for deciding on the
appropriate course of action.

Contact STAR Center, or your Technical Assistance Center Via TechCONNECT or eCONTACT ticket if no
solution is found
Stellantis US LLC

Version 4.5 06/08/2022