HEM Data Products

DAWN OBD Inspector™ with TamperDetect™

Description & Purpose

HEM Data’s DAWN OBD Inspector™ is an inspection/maintenance (I/M) tool for heavy-duty, medium-duty and light-duty diesel vehicles. DAWN OBD Inspector is a small, easily portable solution and quick to install. It is ideal for the roaming inspector or test site. Just attach the hardware to the vehicle network connector, turn on the engine, and open the app. Complete the test and view the report all within 2 minutes! DAWN (Data Acquisition With Network) is the umbrella name for HEM Data’s products.

OBD Inspector acquires all the available data to assess the vehicle’s condition including transmitted parameters, Test Modes in J1979 and Diagnostic Messages (DMs) in J1939, reporting Readiness and DTCs (active, pending, permanent, historical). HD-OBD was phased in during the 2010-2014 model years for on-road trucks. Older models and off-road vehicles are supported if the data is available on the vehicle’s J1939 network.

The tool is designed for federal and state diesel I/M programs, service technicians, researchers, and companies who resell or buy used trucks and off-road vehicles. The California Air Resource Board (CARB) has approved a version of HEM Data’s DAWN OBD Inspector™ for use with their CARB Clean Truck Check. DAWN OBD Inspector is also adaptable to meet inspection data acquisition and analysis requirements of other government jurisdictions.

HEM Data supports program compliance and enforcement (fraud, tampering). DAWN OBD Inspector has been used to evaluate over 75,000 heavy and medium duty trucks that have been acquired by over 150 inspectors. This inspection data is stored in HEM Data’s HD-OBD Inspection Dashboard™. The Inspection Dashboard has an advanced TamperDetect™ algorithm using the HD-OBD data to determine if the vehicle has been tampered to delete or override the emissions system. OBD testing is important for environmental and human health to minimize engine emissions and to have emission equipment operate efficiently. It is illegal to resell vehicles with tampered or deleted emissions.

Below is a screenshot showing key information to the user immediately after the test. The data displayed can be modified for the application. Part of a report shows whether a vehicles emission system was tampered/deleted.

Part of a report showing a tampered vehicle


OBD Inspector consists of three major components

  • CAN Mini Streamer™ hardware (dongle)
  • iPad or iPhone (iOS 12.4 and up)
  • DAWN OBD Inspector™ software
  • HD-OBD Inspector Dashboard™ (database of 75,000+ inspections)

CAN Mini Streamer™ Hardware

HEM Data’s CAN Mini Streamer™ hardware sends the vehicle data to the DAWN OBD Inspector app via WiFi. The Mini Streamer hardware conveniently fits directly on the 9-pin J1939 connector. An adapter cable works for the 16-pin J1939 connector or a non-standard connector. Baud rates of 250k, 500k, and 1000k are automatically detected.

J1939 Mini Streamer™

The Mini Streamer acquires both J1939 and J1979 data within 2 minutes and wirelessly sends vehicle data to the DAWN OBD Inspector™ app. Therefore, test personnel don’t need to climb into the cab.

DAWN OBD Inspector™ Software

HEM Data develops various software apps to support both I/M programs and inspection applications using the CAN Mini Streamer hardware. State and federal agencies as well as fleets, and Independent Owner Operators (IOOs) could benefit. Applications include

  • Specific jurisdiction’s requirements, such as the CARB I/M program
  • Inspection for a re-sale/auction
  • Monitoring fault codes
  • How vehicles are used and to determine pass/fail requirements
  • Detecting tampering for compliance and enforcement

Currently, DAWN OBD Inspector is supported on both an iPad and iPhone. Check with HEM Data regarding the status of PC and Android support. The app displays real-time information to the user as the test is progressing. The app sends the data to HEM Data’s Dashboard (and/or the customers) when the smart device has internet access. The analyzed results are conveniently displayed locally in the app for quick feedback as shown in the sample screen below. A progress bar at the bottom of the screen shows the test status.

Parameters table provides real-time feedback to the user

The screenshot below shows all active, previous, and pending trouble codes on the heavy-duty vehicle.

Active, previous, and pending trouble codes

HD-OBD Inspector Dashboard

HEM Data’s HD-OBD Inspection Dashboard analyzes both J1939 and J1979 data. This is important since J1939 Diagnostic Message (DM) equivalents are reported very differently in J1979.

Using HEM Data’s TamperDetect™ algorithm, the dashboard analyzes whether the vehicle’s OBD system and emission control equipment have been tampered or deleted. The vehicle report is available directly from the app so the user feedback is nearly instantaneous on the iPad or iPhone.

Additional features of the Inspector Dashboard are

  • Define pass/fail criteria for a HD I/M program
  • Define normal/abnormal data for given models
  • Compare vehicle models within a user-defined group (can be very specific or broad)
  • Determine what parameters are commonly transmitted to thereby know what parameters will be available

Intermittent Problems

To help the service technician gain valuable data to fix a frustrating intermittent problem, the OBD or J1939 Mini Logger should be temporarily installed to record vehicle operation. The technician selects the parameters of interest to log based on the problem. See examples showing intermittent problems that we were successfully diagnosed.


HEM Data consults on acquiring and analyzing OBD data. HEM Data has an ongoing multiple year support contracts with EPA starting six years ago. EPA and CARB have acquired over 800 HEM Data loggers. SAE has published two books written by HEM Data on acquiring OBD and other CAN data from LD and HD vehicles, and SAE has requested updated editions for these books.

Presentation to I/M Solutions Forum

HEM Data made a presentation at the I/M Solutions Forum introducing DAWN OBD Inspector. A copy of the presentation can be downloaded here.

J1939 Mini Logger™ OBD Mini Logger™ DAWN Telematics™ DAWN™ Software ADAQ Mini™ DAWN Dashboard™