What are the ELD Malfunctions and Data Diagnostic Events?

Nov 7, 2022 2:17:05 PM / by Mike Riegel

According to the ELD requirements, electronic logging devices are supposed to log certain events as malfunctions or data diagnostic events if the device can't acquire all required data items. Some ELD providers will indicate these items as a "malfunction" or "data diagnostic" with little information about the cause. This can confuse and worry users into thinking their ELD is broken and leaving them exposed for DOT violations for not having a working ELD.

All ELD must have a special malfunctions and data diagnostic event indicator on their display that is always visible to the user. This should be able to be seen by the driver on every screen in accordance with the ELD mandate.

After the malfunction has fallen out of the required timeframe in a 24-hour window the indicator should go away, indicating that the malfunction is no longer active.

Here are the different types of malfunctions all ELDs must be able to catch. 


Power Compliance Malfunction

From the FMCSA mandate this malfunction must be handled by the ELD as follows: Power Compliance Monitoring
(a) An ELD must monitor data it receives from the engine ECM or alternative sources as allowed in sections– of this appendix, its onboard sensors, and data record history to identify instances when it may not have complied with the power requirements specified in section, in which case, the ELD must record a power data diagnostics event for the corresponding driver(s), or under the unidentified driver profile if no drivers were authenticated at the time of detection.

(b) An ELD must set a power compliance malfunction if the power data diagnostics event described in paragraph of this appendix indicates an aggregated in-motion driving time understatement of 30 minutes or more on the ELD over a 24-hour period across all driver profiles, including the unidentified driver profile.

What this means is that when the vehicle with the ELD is started, it is required to boot up and begin working within 1 minute after the vehicle is started and remain on until the vehicle is turned off.

If this item is not collected for a cumulative period of 30 minutes or more within a 24-hour window the display must show a malfunction indicator. This time window is for all accounts including the "unidentified driver" account. 

avoid eld malfunctions and data diagnostic events


Engine Synchronization Compliance Malfunction

The engine synchronization malfunction deals with the data that is collected from the vehicle's engine that is used to keep the driver's hours of service records. These required items are:

  • The VIN of the vehicle
  • The total engine hours on the vehicle
  • The current odometer reading
  • The wheel speed of the vehicle to tell if it is in motion
  • The RPM to tell that the engine is running.

According to the FMCSA's ELD Mandate engine synchronization events must be handled as follows: Engine Synchronization Compliance Monitoring

(a) An ELD must monitor the data it receives from the engine ECM or alternative sources as allowed in sections– of this appendix, its onboard sensors, and data record history to identify instances and durations of its non-compliance with the ELD engine synchronization requirement specified in section 4.2.

(b) An ELD required to establish a link to the engine ECM as described in section 4.2 must monitor its connectivity to the engine ECM and its ability to retrieve the vehicle parameters described under section 4.3.1 of this appendix and must record an engine-synchronization data diagnostics event when it no longer can acquire updated values for the ELD parameters required for records within 5 seconds of the need.

(c) An ELD must set an engine synchronization compliance malfunction if connectivity to any of the required data sources specified in section 4.3.1 of this appendix is lost for more than 30 minutes during a 24-hour period aggregated across all driver profiles, including the unidentified driver profile.


If the ELD is unable to get any one of the 5 items within 5 seconds of making the request on the vehicles ECM, then a data diagnostic event must be triggered to let the driver know of a possible error. 

If the data diagnostic event continues and cannot get the required engine data for a cumulative period over 30 minutes in a 24-hour window across all user profiles, then the data diagnostic event must be upgraded to an "Engine synchronization compliance" malfunction event.


Timing Compliance Malfunction

The timing compliance data required by the mandate works off the ELD's ability to collect and use Coordinated Universal Time (UTC) time to log and monitor events. The timing of the ELD cannot be adjusted or tampered with by anyone (drivers, carriers, employees etc).

The time used by the electronic logging device must be collected automatically and a malfunction must be indicated if the ELD cannot meet the underlying requirement set in the mandate. Timing Compliance Monitoring
The ELD must periodically cross-check its compliance with the requirement specified in section of this appendix with respect to an accurate external UTC source and must record a timing compliance malfunction when it can no longer meet the underlying compliance requirement.

The underlying compliance requirement mentioned says that the electronic logging device must stay in sync with the UTC time and if the synchronization deviates by more than 10 minutes in any direction then the malfunction event must be triggered.


Positioning Compliance Malfunction

The ELD is required to get the driver's current position in order to determine things such as total distance traveled and where the driver was when ELD events trigger. 

The ELD must be constantly monitoring the latitude and longitude of the vehicle with an accuracy of at least 1 mile while on duty and an accuracy of 10 miles while in personal conveyance

According to the FMCSA's ELD Mandate positioning compliance events must be handled as follows: Positioning Compliance Monitoring

(a) An ELD must continually monitor the availability of valid position measurements meeting the listed accuracy requirements in section of this appendix and must track the distance and elapsed time from the last valid measurement point.

(b) ELD records requiring location information must use the last valid position measurement and include the latitude/longitude coordinates and distance traveled, in miles, since the last valid position measurement.

(c) An ELD must monitor elapsed time during periods when the ELD fails to acquire a valid position measurement within 5 miles of the CMV’s movement. When such elapsed time exceeds a cumulative 60 minutes over a 24 hour period, the ELD must set and record a positioning compliance malfunction.

(d) If a new ELD event must be recorded at an instance when the ELD had failed to acquire a valid position measurement within the most recent elapsed 5 miles of driving, but the ELD has not yet set a positioning compliance malfunction, the ELD must record the character ‘‘X’’ in both the latitude and longitude fields, unless location is entered manually by the driver, in which case it must log the character ‘‘M’’ instead. Under the circumstances listed in this paragraph, if the ELD event is due to a change in duty status for the driver, the ELD must prompt the driver to enter location manually in accordance with section of this appendix. If the driver does not enter the location information and the vehicle is in motion, the ELD must record a missing required data element data diagnostic event for the driver.

(e) If a new ELD event must be recorded at an instance when the ELD has set a positioning compliance malfunction, the ELD must record the character ‘‘E’’ in both the latitude and longitude fields regardless of whether the driver is prompted and manually enters location information.

If the ELD is unable to connect to the needed satellites in order to get position, then the ELD must start its data diagnostic errors. If the ELD cannot get the location data for a cumulative 60 minutes in a 24-hour period, the event must be upgraded to a malfunction. 

When trying to log missing location information in the ELD's database the latitude and longitude must contain an "X" symbolizing that the location data could not be received. If the driver manually enters a location, then the fields will need to contain an "M".


Data Recording Compliance Malfunction

After a period of frequent use an ELD may begin to run out of memory to store new data for logs. If an ELD does not have a way to purge old data or make room for new data, it's possible that it will reach its limits in terms of available memory. 

It is also possible that the ELD was unable to get one or many required data items for logging. If any of the required data items are unable to be collected, then the ELD must indicate a diagnostic data error. Data Recording Compliance Monitoring

(a) An ELD must monitor its storage capacity and integrity and must detect a data recording compliance malfunction if it can no longer record or retain required events or retrieve recorded logs that are not otherwise catalogued remotely by the motor carrier.

(b) An ELD must monitor the completeness of the ELD event record information in relation to the required data elements for each event type and must record a missing data elements data diagnostics event for the driver if any required field is missing at the time of recording.


Data Transfer Compliance Malfunction

Being able to transfer data and logbooks to the DOT at roadside is essential. The ELD must always be able to transfer logs as required by the FMCSA.

A certified ELD must periodically test its data transfer mechanism to make sure that it is operational. This test should be performed at least once every 7 days. If for some reason it fails to perform its check then the ELD should produce a data diagnostic error. Once the data diagnostic error is present the ELD should automatically increase the frequency of its data transfer testing to once every 24 hours. Data Transfer Compliance Monitoring

(a) An ELD must implement in-service monitoring functions to verify that the data transfer mechanism(s) described in section 4.9.1 of this appendix are continuing to function properly. An ELD must verify this functionality at least once every 7 days. These monitoring functions may be automatic or may involve manual steps for a driver.

(b) If the monitoring mechanism fails to confirm proper in-service operation of the data transfer mechanism(s), an ELD must record a data transfer data diagnostic event and enter an unconfirmed data transfer mode.

(c) After an ELD records a data transfer data diagnostic event, the ELD must increase the frequency of the monitoring function to check at least once every 24-hour period. If the ELD stays in the unconfirmed data transfer mode following the next three consecutive monitoring checks, the ELD must detect a data transfer compliance malfunction.


Other ELD Detected Malfunction

Sometimes ELD providers may add additional features outside of the ELD mandate to their product or services. If these providers need to alert the user of possible malfunctions of these other items, they can use the malfunction events to get the driver's attention. Other Technology-Specific

Operational Health Monitoring In addition to the required monitoring schemes described in sections– of this appendix, the ELD provider may implement additional, technology-specific malfunction and data diagnostic detection schemes and may use the ELD’s malfunction status indicator and data diagnostic status indicator (described in sections and to communicate the ELD’s malfunction or non-compliant state to the operator(s) of the ELD.


If you find that you have any of these ELD malfunctions showing up in your ELD's display, follow these steps on how to handle ELD malfunctions to protect yourself from possible DOT violations.

If you follow these steps and still receive a violation in error, remember you can always contest it by filing a DataQ and getting the violation and inspection removed so it won't affect your CSA score.

If you want to review the entire ELD mandate, you can download it here.

Topics: ELDs

Mike Riegel

Written by Mike Riegel