Countries:

CANADA, UNITED STATES Document ID: IK1201515

Availability:

ISIS, FleetISIS, NotSIR

Revision:

0

Major System:

ENGINE

Created:

6/2/2025

Current Language: English

Last Modified: 6/13/2025

Other Languages: NONE

Author:

Viewed:

Brandon Heisler

316
Less Info

Coding Information

Hide Details

Copy Link

Copy Relative Link

Bookmark

Add to Favorites

Print

Provide Feedback

View My Bookmarks

Helpful

Not Helpful

1

0

Title : Supplemental 2017 A26 (A26A) Misfire Diagnostics
Applies To : 2017 A26 ESN 4500000 - 4599999

CHANGE LOG
Please refer to the change log text box below for recent changes to this article:
06/13/2025 - Initial Article Release

**PLEASE COMPLETE ALL PUBLISHED DIAGNOSTICS BEFORE PERFORMING THESE STEPS**
The diagnostics within this document are supplemental diagnostic steps only. This article is intended to be followed when all published diagnostics have been exhausted and there is no
current repair direction or solution. Failure to follow published diagnostics can result in improper diagnostics being performed, and may also lead to extended downtime for the customer.
Technical Service Support teams have created this article for a short-term solution while pending published diagnostics are enhanced and updated. Once those diagnostics have been
updated, this article will be retired. Always reference published manuals, FCAPs, and GUIDE sessions before performing the steps below.

DESCRIPTION
This document will guide the user through supplemental diagnostic steps for misfire faults and symptoms on a 2017 A26 (A26A).

SYMPTOM(s)
Diagnostic Trouble Code(s) & Dashboard Indicator Light(s):
DTC/Light

Description

SPN 1322 FMI 14

Engine Misfire for Multiple Cylinders: Special Instructions

SPN 1322 FMI 31

Engine Misfire for Multiple Cylinders: Condition Exists

SPN 1323 FMI 31

Engine Misfire Cylinder #1: Condition Exists

SPN 1324 FMI 31

Engine Misfire Cylinder #2: Condition Exists

SPN 1325 FMI 31

Engine Misfire Cylinder #3: Condition Exists

SPN 1326 FMI 31

Engine Misfire Cylinder #4: Condition Exists

SPN 1327 FMI 31

Engine Misfire Cylinder #5: Condition Exists

SPN 1328 FMI 31

Engine Misfire Cylinder #6: Condition Exists

Customer Observations or Concerns:
MIL
Misfire
Rough Running

SPECIAL TOOL(s) / SOFTWARE

Tool Description

Tool Number

Comments

Instructions

SDS

N/A

N/A

N/A

Tools Resource Center

SERVICE PARTS INFORMATION
Please consult your parts department for service part information. Ensure you are using the most current service part numbers.

DIAGNOSTIC STEP(s)

Step

Interpret the fault codes.

Decision

Determine the proper diagnostic direction:

Yes.

Are more than two single-cylinder misfire fault codes present in the recent health
report, or multiple cylinder misfire fault codes present with more than 1 singlecylinder misfire fault?

If you have not already done so, perform
diagnostics for the multiple-cylinder
misfire fault code.
If the diagnostics for the multiple-cylinder
misfire have been followed, and no
trouble found, confirm base airflow and
fuel system performance.

#1

IK1201511 and IK500109 can be followed
to assist with diagnostics.

No.
Proceed to step 2.

Step
#2

Confirm base diagnostics have been performed.
Review FCAP/GUIDE and symptom-based diagnostics from the diagnostic
manual:
Did the applicable FCAP/GUIDE or symptom-based diagnostics identify a repair
path?

Decision
Yes.
Follow the repair path established by the
published diagnostics.

NOTE: If the GUIDE session led to cylinder head replacement due to valve
recession measurements or injector replacement, that repair path should be
followed and the issue re-tested BEFORE opening a tech service case file.

NOTE: If the issue persists after
following the repair path, ensure the
GUIDE was followed to completion,
and then proceed to step 3.

Tech service does NOT provide approval for part or component replacement. If
a failure has been identified through published diagnostics, then repairs or
replacements for such should be performed.

No.
Proceed to step 3.

Step

Verify the misfire.

Decision

Perform a cylinder balance test using SDS.

Yes.

Get the unit up to operating temperature.

Re-test for the misfire fault. If the issue
persists, open a tech service case file with
your step-by-step results from this article,
as well as GUIDE completion code.

In ONE snapshot, using the cruise switches to hold engine RPM ONLY, hold
the RPM for one minute at idle, one minute at 1200 RPM, and one minute at
1500 RPM.
Graph the engine RPM and all 6 cylinder velocities in SDS. Check for any
outliers in cylinder velocity. Especially related to the cylinder with the fault
code:
#3

Are all cylinders within 0.3 degrees of -0.6 degrees during the steady RPMs (not
during RPM climb)?
NOTE: Using the accelerator pedal to perform this test is NOT acceptable.
Engine RPM is typically not steady enough to get an accurate reading of
cylinder velocity. If the cruise switches are not operational to ramp and hold
engine RPM, then body controller and/or ECM programming may be required.
Image #1 - Good Cylinder Balance

No.
Proceed to step 4.

Image #2 - Single Cylinder Misfire
Image #3 - Multiple Cylinder Misfire

Step

Verify compression brakes.
Remove both compression brakes and install shorter rocker bolts, PN:
06021910616, or 40 mm spacers if the shorter bolts are not available.
Perform the cylinder balance test again in the same manner as step 3:

Decision
Yes.
Replace the compression brake assembly
associated with the cylinder that was out
of specification, and then re-test.

Is the cylinder balance test now in specification, with all cylinders within 0.3 degrees
of -0.6 degrees?
NOTE: If the issue persists after
repairs, revisit step 3.

#4

No.
Proceed to step 5.

Step
#5

Verify valve height.
While the compression brakes are still removed, perform the exhaust valve
recession inspection measurements from the A26 diagnostic manual:

Decision
Yes.
Proceed to step 6.

Are all exhaust valves in specification?
NOTE:
Typical good valve recession is between 0.145 and 0.160.

No.

Failed valve recession measurements are typically between 0.161 and 0.175.
If measurements taken are below 0.145 or greater than 0.175, then the
measurement is likely not accurate and should be verified.

Step

Remove the cylinder head. Inspect the
cylinder head per IK1201476. Rebuild or
replace depending on the results of the
article. Once repairs are completed, retest for the issue.

Verify injector replacement.

Decision

Review the R/O and warranty history to check for recent injector replacement: Yes.
Has the injector for the identified cylinder been replaced within the past 5,000 miles? Remove the cylinder head. Inspect the
cylinder head per IK1201476. Inspect for
possible internal engine damage or wear.
Once repairs are completed, re-test for
the issue.

#6

No.
Replace the injector for the identified
cylinder and then re-test for the issue.
NOTE: If the issue persists after
repairs are completed, revisit step 3.

Step #3 - Image #1: Good Cylinder Balance
Item 1: Ideal graph selection points. RPM is stable and not rising.
Item 2: Data table showing all cylinders within 0.3 degrees of -0.6

Step #3 - Image #2: Single-Cylinder Misfire
Item 1: Graph Selection Point. Engine RPM is stable.
Item 2: Data table showing most cylinders within 0.3 degrees of -0.6
Item 3: Cylinder 6 misfire. Data showing reading of -1.3 degrees. Outside the allowable 0.3 degrees from -0.6

Step #3 - Image #3: Multiple-Cylinder Misfire
Item 1: Graph Selection Point. Engine RPM is stable. This example shows the engine at idle (600 RPM)
Item 2: Data table showing most cylinders outside 0.3 degrees of -0.6.
Item 3: Cylinders 1, 4, 5, and 6 misfiring at idle.

REPAIR STEP(s)
Please see the service manual for current service and repair procedures.

WARRANTY INFORMATION
Warranty Claim Coding:
Refer to the Warranty Coding Manual for Group and Noun Codes.

Standard Repair Time(s):
Refer to the SRT Manual for Repair Times

OTHER RESOURCES
Master Service Information Site

Hide Details

Feedback Information
Viewed:

315

Helpful:

1

Not Helpful: 0
No Feedback Found

Copyright © 2025 Navistar, Inc.