Electronic Diesel Engine Diagnosis Specialist Certification Test
Objective: To identify those Technicians who possess knowledge of the skills necessary to diagnose sophisticated diesel engine performance problems on medium- and heavy-duty trucks.
Test Content
The Electronic Diesel Engine Diagnosis Specialist (L2) test contains 45 questions focused on the diagnosis of general diesel engine, electronic diesel engine controls, diesel engine air induction and exhaust systems, diesel fuel systems, and specific fuel systems, including High Pressure Common Rail (HPRC), electronic unit injector (EUI) and hydraulic electronic unit injector (HEUI) systems. Because of the complexity of the L2 test, ASE generally recommends that you NOT register for other tests during the same test session.
Composite Vehicle
Many of the questions relate to a sample vehicle equipped with a composite diesel engine control system featuring a cross-section of electronic diesel engine control technology used by all engine manufacturers. This vehicle is described in the Medium-Heavy Composite Vehicle Type 4 Reference document that is provided as an electronic pop-up during the test. Use the link below to download and review this document prior to taking the L2 test.
Prerequisite
To register for the regular L2 certification test, you must have passed one of the ASE Diesel Engine tests (A9, H2, S2, or T2) and one of the ASE Electrical/Electronic Systems tests (A6, H6, S6 or T6). To register for the recertification version of the Electronic Diesel Engines Diagnosis Specialist Test (L2R), you must have previously passed the regular L2 test.
Recertification
Technicians must retest every five years to retain their certification. The Advanced Diesel Engine Diagnosis Specialist recertification test (L2R) is the same length as the regular certification test.
Study Guides
This guide contains test specifications, tasks lists, sample test questions, and training resources.
Advanced Diesel Engine Diagnosis Specialist Study Guide:This guide contains test specifications, tasks lists, sample test questions, and training resources.
Medium-Heavy Composite Vehicle Type 4 Reference Booklet:This booklet describes the composite electronic diesel engine control system that is used with many of the questions in the L2 test.
Established to ensure test prep content accurately reflects current ASE standards and task lists, the Officially Licensed ASE Test Prep Partners go through a comprehensive content and ASE style guide review process. ASE works directly with approved partners to help verify that their materials accurately support candidates preparing for ASE certification tests.
Test Times and Number of Questions
ASE Certification tests usually include ten additional research questions that are not counted for score. You will not be told which questions these are, so you should answer every question. No research questions are added to Recertification Tests. You are only eligible to take the Recertification Test when you have previously passed the corresponding initial Certification Test.
| Test | Name | Certification Tests: Number of Questions | Certification: Time Allowed | Recertification Tests: Number of Questions | Recertification: Time Allowed |
|---|---|---|---|---|---|
| L2 | Electronic Diesel Engine Diagnosis | 45 | 2 hours | 45 | 2 hours |
Registration Dates
Winter Registration
January 10, 2026 - March 31, 2026
Spring Registration
April 10, 2026 - June 30, 2026
Summer Registration
July 10, 2026 - September 30, 2026
Fall Registration
October 10, 2026 - December 31, 2026
Testing FAQs
ASE Certification tests are written in workshops by a national panel of seasoned automotive industry professionals, including working technicians, automobile manufacturers, aftermarket manufacturers, and educators. Not by any single person at ASE.
Exams are segmented by sub-specialty such as automobile, medium/heavy truck, school bus, collision repair, and more. There are over 50 tests, each designed to discern the automotive service technician’s knowledge of job-related skills.
Purchasing and scheduling a test can be done by logging in to your myASE account. To purchase a test, select the test you want to take and pay the applicable fees. A registration fee is charged per order in addition to the test fee. Once you have purchased a test, you will have 90 days from the original date of purchase to schedule an appointment and take your test. Visit myASE to get started.
Certification credentials are valid for five years. If it has been five years or more since you took a test, it’s time to take the corresponding Recertification Test. The five-year requirement ensures certified professionals are current in this rapidly changing industry. You can find your expiration dates on your certificates or in myASE.
You may take the Recertification Tests even if your credentials have expired. You simply must have been previously certified in that specialty area. If you have some certifications that expire soon and others that are still good for some time, you may take Recertification Tests for any or all of them. If you recertify early, you will not be credited with the time remaining on your original certification. The new expiration date occurs five years from the date of your recertification.
If you wish to change your test date or time, you must first cancel the existing appointment before you can schedule a new one. No changes are allowed within three days of your scheduled appointment. To make changes, use the Cancel Selected Appointment(s) option in myASE. For assistance by phone, call ASE Customer Care at 800-390-6789 from 8AM – 5PM Eastern Monday – Friday.
If you wish to cancel a test, you must first cancel any existing appointment for that test AND then cancel the test. Use the Cancel Test option in myASE. If you are within three days of your testing appointment, you cannot cancel the appointment or test. You can only cancel a test and receive a refund for a test that you purchased. For assistance by phone, call ASE Customer Care at 800-390-6789 from 8AM – 5PM Eastern Monday – Friday.
To become ASE Certified, you must pass an ASE test and have full-time, hands-on work experience (or a combination of formal training and experience). The amount of work experience required can vary by test.
It is best to submit your work experience form for review after you have created a myASE account. It does not have to be submitted before you take your test, but your certificate for a passed test will be delayed until your work experience information is reviewed and approved. See the work experience requirements here and complete the work experience form online.