What is OBD: Understanding on-board diagnostics for your fleet

Managing a fleet of vehicles comes with constant challenges, such as unexpected breakdowns that disrupt your operations, rising maintenance costs, and the ongoing pressure to meet regulatory requirements. In fact, downtime costs as much as an average of $448 to $760 a day per vehicle.

That’s why understanding on-board diagnostics (OBD) is an essential component for your fleet management strategy. OBD is a critical diagnostic system in modern vehicles that enables real-time monitoring of engine performance and emissions. They have become so important for vehicle diagnostics and preventative maintenance that the California Air Resources Board (CARB) requires that all new vehicles sold in California from 1988 onward need to have some basic OBD capability.

In this comprehensive guide, we’ll explore what OBD is, OBD II protocols, common DTC codes, and how technology like Samsara’s Connected Asset Maintenance solution can help fleets reduce downtime, improve productivity, and maximize profitability.

What is On-Board Diagnostics (OBD)? 

On-Board Diagnostics (OBD) is a standardized computer system in your vehicles that continuously monitors and reports on the health and performance of critical vehicle information from the engine, emissions system, and other key components. There are two generations of OBD:

• OBD (On-Board Diagnostics): Introduced in the early 1980s by the Society of Automotive Engineers (SAE), OBD (or OBD1) used manufacturer-specific systems with no standard codes or connectors. The onboard computer would provide basic fault detection, like triggering the check engine light, and offer limited data access. Each automaker had its own tools, so a scanner for one brand wouldn’t work on another. These systems were common in vehicles built before model year 1996.

• OBD-II: Introduced in 1996, OBD-II (or OBD2) standardized diagnostics across all U.S. vehicles with a universal 16-pin connector and shared diagnostic trouble codes (DTCs). It offers detailed real-time data like revolutions per minute (RPM), oxygen sensor readings, and emissions status. OBD-II systems are typically compatible with most OBD-II scanners, allowing access to a wide range of vehicle systems, including engine, transmission, and emissions components, regardless of the vehicle's brand.

A key part of how this technology works involves OBD II protocols. These protocols define how diagnostic trouble codes (also known as OBD II fault codes) and other data are communicated from your vehicle’s control modules to an external device. By standardizing data exchange, OBD II protocols ensure consistent, reliable diagnostic information across most modern vehicles.

The primary components of an OBD system include:

• Vehicle OBD-II port: A standardized 16-pin diagnostic link connector (DLC) that provides access to your vehicle’s diagnostic data. If your vehicle doesn’t support a standard OBD-II port, you can use an OBD-II adapter instead.

• Scan tool: A device that plugs into the OBD port to read DTCs, view real-time data, and perform diagnostic tests.

• Diagnostic trouble codes (DTCs): Standardized error codes that identify specific issues detected by the OBD system, helping you or your technicians pinpoint and resolve problems efficiently.

For your fleet, onboard diagnostic systems serve as an early warning system, providing diagnostic trouble codes (DTCs) that help you identify potential issues before they escalate into major repairs or roadside breakdowns. This proactive approach to vehicle maintenance can help reduce your downtime and operational costs.

Understanding OBD protocols and scanner usage

Knowing how OBD protocols work and how to properly use OBD scanners is critical for developing a comprehensive vehicle maintenance strategy. Each vehicle manufacturer may use different communication protocols to transmit data from the vehicle’s computer to diagnostic tools. Understanding these protocols ensures you select compatible scanners that accurately read and interpret the data, avoiding misdiagnosis or incomplete information.

What are the five main OBD-II protocols?

OBD protocols are the communication languages that your vehicle’s computers use to share information with diagnostic tools. The five main OBD-II protocols include:

1. SAE J1850 PWM: Used primarily in Ford vehicles.

2. SAE J1850 VPW: Common in General Motors vehicles.

3. ISO 9141-2: Found in many European and Asian vehicles.

4. ISO 14230 (KWP2000): An advancement of ISO 9141-2 with enhanced capabilities.

5. ISO 15765 CAN: The newest protocol, mandatory on all vehicles sold in the US since 2008.

The protocol ensures that the scanner can properly communicate with the vehicle’s system to request and receive these DTCs. Without the correct protocol, the scanner won’t understand the data format or be able to retrieve the trouble codes accurately. Most modern OBD scanners support multiple protocols, but it’s worth confirming compatibility before purchase.

What are common OBD-II DTC codes?

Once the OBD-II protocol transmits the Diagnostic Trouble Codes (DTCs), your maintenance team can then proceed with diagnosing and servicing the vehicle. Here is a list of some of the most common OBD-II DTC codes that you need to know:

• P0300: A random or multiple cylinder misfire, commonly caused by worn spark plugs, ignition coil failures, or inconsistent fuel delivery.

• P0420: The catalytic converter on Bank 1 is not operating efficiently, often due to a degraded converter or a faulty upstream oxygen sensor.

• P0171: The engine is running too lean on Bank 1, typically caused by unmetered air entering the system, such as from vacuum leaks or a malfunctioning MAF sensor.

• P0174: The engine is running too lean on Bank 2, usually due to the same issues as P0171, affecting the opposite engine bank in V-type engines.

• P0442: A small leak in the vehicle’s evaporative emission control (EVAP) system, frequently caused by a loose gas cap, cracked hose, or faulty seal.

• P0455: A large leak detected in the EVAP system, often resulting from a missing gas cap, disconnected hose, or failed vapor canister.

• P0128: The engine coolant is not reaching its optimal operating temperature, typically caused by a stuck-open thermostat or a faulty temperature sensor.

• P0101: A performance issue with the mass airflow (MAF) sensor or its circuit, which can result in incorrect air-fuel mixture readings and poor engine response.

• P0133: The oxygen sensor (Bank 1, Sensor 1) is responding slower than expected, which may lead to reduced fuel efficiency and higher emissions.

• P0700: A general transmission control system malfunction, often indicating other transmission-related codes are stored in the transmission control module (TCM).

Take your maintenance operations to the next level with Samsara Connected Asset Maintenance

While OBD systems are essential to minimizing breakdowns and keeping your fleet up and running, modern organizations today are adopting computerized maintenance management system (CMMS) solutions like Samsara’s Fleet Maintenance solution to take their maintenance operations to the next level.

Samsara Connected Asset Maintenance solution is the only CMMS solution built on Samsara Intelligence. By harnessing the power of your fleet's data, you can save time and boost utilization, track costs for deeper insights, and consolidate systems for streamlined workflows.

Samsara Connected Asset Maintenance is a user-friendly platform engineered to minimize the time your vehicles spend in the shop and maximize their time on the road, directly impacting your bottom line. By consolidating critical maintenance information and streamlining key workflows, you can:

• Accelerate work order creation with automated data: Inputting a vehicle number instantly populates work order details in a holistic view on a single dashboard, resulting in a process that takes less than a minute to complete and submit. 

• Track costs and uncover problem areas: With Samsara’s Maintenance Cost reporting tool, you can integrate both internal and external vendor spend, allowing you to analyze trends by region, vehicle or asset make, service category, and more.

• Consolidate systems and processes: By having a single point of access to DVIRs, preventive maintenance, and active issues fleet-wide on a unified dashboard, you can easily understand the overall health of your operations and prioritize labor, costs, and maintenance effectively. Furthermore, you can streamline maintenance operations with native integrations and third-party APIs.

• Harness AI to reduce manual processes and improve maintenance: Use Samsara Intelligence to leverage smart alerts to quickly surface fault codes. This makes it possible  to efficiently prioritize repairs and streamline the repair process with AI-generated action steps and instructions for technicians that you can customize to your fleet.

Sterling Crane Canada is the 10th-largest mobile crane rental company in the world. By leveraging Samsara Vehicle Telematics, they were able to improve their proactive maintenance by 14%, while saving over $517,000 in annual maintenance labor costs and 10,000+ hours in technicians’ time. Technicians can now focus on their core tasks instead of troubleshooting malfunctioning equipment or being incorrectly deployed for repairs. These newfound insights have also uncovered significant cost savings, including $1.1 million saved in maintenance and replacement costs overall for on-road equipment and over $2.1 million saved overall for off-road equipment.

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Learn how Samsara can help you improve fleet maintenance by exploring our Fleet Telematics solution and get in touch with our team today.