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ELD Technical Specifications FAQs

NOTE:  This guidance revises FMCSA-ELD-Technical-Specifications-FAQs(2018-04-09), issued on April 9, 2018, and rescinded on March 10, 2022.




ELD Technical Specifications FAQs

Question: Why are technical specifications in the Electronic Logging Device (ELD) rule?

Guidance: The technical specifications in the ELD rule ensure that manufactures develop compliant devices and systems for uniform enforcement of hours of service.

Question: Will FMCSA allow ELD providers to access the Electronic Record of Duty Status (eRODS) application for use in testing how their electronic logging device’s (ELD) data will display to safety officials? 

Guidance: FMCSA has made a web-based version of the eRODS software available for use by motor carriers and ELD providers. Motor carriers and ELD providers may upload an ELD file to see how the hours of service data will be presented to a safety official. Web eRODS is available on the ELD website at  

Question: How will the ELD report on-duty not-driving status when the origin of the duty status is automatic instead of driver-input?

Guidance: The ELD will report on-duty not-driving status based on automatic detection, starting from the time the vehicle is no longer in motion.

Question: The Event Checksum Calculation describes the individual items to be included in the calculation. Number 9 says “CMV Number.” Is this the CMV VIN or the CMV Power Unit Number?

Guidance: FMCSA showed a CMV number, as an example, in the header output file. The intent was to allow an additional vehicle identification number if an operator had numbered vehicles and chose to add company-assigned numbers to the CMV header data.
NOTE: The following guidance reflects minor correction(s) (e.g., for grammar, typographical errors, or consistency) made on March 10, 2022.

Question: Is a physical connection between the electronic control module (ECM) and electronic logging device (ELD) required to establish integral synchronization with the engine?

Guidance: No. The ECM and ELD may be connected by serial or Control Area Network communication protocols. Hard wiring to the J1939 plug and Bluetooth® connectivity are examples of methods of receiving the data from the ECM or vehicle data bus.

Question: If an electronic logging device (ELD) loses connection to the electronic control module (ECM), how will the device report a system failure?

Guidance: An ELD must use onboard sensors and data record history to identify instances when it may not have complied with the power requirements specified in the ELD rule.

Question: Must the manufacturer self-certify and register every version or firmware update to the electronic logging device (ELD)?

Guidance: The manufacture must register each model and version and self-certify that each particular ELD is compliant with the ELD rule. The manufacturer must decide whether a firmware update is sufficiently significant to change the registration information. FMCSA does not specify parameters for version revisions.

Question: Are vendors required to update or register each different configuration of hardware, even though the product is the same as an application (app) (e.g., black box and Samsung, black box and iPhone, black box and Nexus)?

Guidance: Vendors should register each device bundle if they have different operating systems (e.g., an iOS-based bundle and an Android-based bundle would be considered two registered devices).

Question: Does the registration process require companies to exclusively use FMCSA’s test procedure? Will vendors have access to testing facilities for electronic logging devices (ELDs)?

Guidance: No. ELD manufacturers may use any test procedure they choose and note this in the registration. FMCSA will not provide a third-party testing service. FMCSA will only investigate devices that are suspected of not conforming to specifications, and will conduct testing with the FMCSA compliance test procedure during its investigation.

Question: How will commercial motor vehicle (CMV) environmental specifics be tested with the electronic logging device (ELD)—for example, mounting and connections to the electronic control module (ECM)?

Guidance: FMCSA does not specify testing requirements for connectivity with the vehicle. Each ELD provider is responsible for connectivity testing.

Question: What is the Event Checksum Calculation? 

Guidance: The Event Checksum Calculation is a value associated with each ELD event at the instance of the event record being created. It describes the individual items to be included in the calculation.  The individual items included in the calculation are listed in sections of 49 CFR part 395, subpart B, Appendix A.

Question: Are unassigned driving reports required to be available at roadside?

Guidance: Yes. Section of 49 CFR part 395, subpart B, Appendix A requires the inspected driver’s profile and the Unidentified Driver profile to be available as separate reports at roadside either by printout or display. If there are no unidentified driver records existing on the electronic logging device (ELD) for the current 24-hour period or for any of the previous 7 consecutive days, an ELD does not need to print or display unidentified driver records for the authorized safety official. Otherwise, both reports must be printed or displayed and provided to the authorized safety official.

Question: How should the electronic logging device (ELD) handle the dashboard odometer display not matching the odometer value returned by the electronic control module (ECM)? For instance, when the engine is replaced and the value is not synchronized.

Guidance: The ELD is required to obtain and display the ECM value at all times. Safety officials will use the odometer value reported on the ELD. Note that documentation of engine changes is required by 49 CFR part 379 Appendix A to be maintained at the carrier’s place of business.
Note: This guidance document does not have the force and effect of law and is not meant to bind the public in any way.  It is intended only to provide information and clarity regarding existing requirements under the law or agency policies. 

Regulatory Topic: ELD Guidance
Effective Date: Thursday, March 10, 2022
Issued Date: Thursday, March 10, 2022