Will Fixd Work On A Diesel?

The Fixd ($59.00 at Amazon) is a little gadget that fits into your car’s On-Board Diagnostic (OBD) connection and gives you access to the car’s computerized self-diagnosis system. The OBD-II port, which is normally positioned under the dashboard on the driver’s side, is found in all cars made after 1996. The Fixd sensor works on all gasoline-powered automobiles with an OBD-II port, but not on cars built before 1996, nor on cars powered by diesel engines or cars that are entirely electric. It will, however, operate on hybrid vehicles.

Do OBD2 scanners work on diesels?

Onboard diagnostic (OBD) systems were first developed and optimized for gasoline engines, but they are now widely used in diesel engines as well. All diesel-powered vehicles with a gross vehicle weight rating (GVWR) of less than 14,000 pounds must now comply with OBDII criteria for monitoring the functioning of their pollution control systems as of the 2007 model year.

“But nothing can be considered to be certain in this world except death and taxes,” wrote Benjamin Franklin. If Franklin could see into the future, he would almost certainly have added ever-stricter pollution control measures to his list. Standards have only been tougher since the California Air Resources Board (CARB) first started regulating pollutants that had a negative influence on the state’s air quality, and technology has been constantly developing to meet these new difficulties.

Diesel automobiles are no strangers to OBD systems. In 1994, CARB and the US Environmental Protection Agency (EPA) mandated OBDII for light-duty diesel vehicles (GVWR less than 8,500 pounds) beginning in 1997. California legislation mandated OBDII compliance for all medium-duty trucks (8,500 to 14,000 pounds GVWR), including gasoline and diesel-powered, starting in 1997. However, the EPA did not immediately follow California’s lead in this area, allowing federal vehicles with GVWRs of 8,500 to 14,000 pounds to be exempt from OBDII compliance. The government required the use of onboard diagnostic devices, although they did not have to be as comprehensive as those required for California automobiles.

It became evident that improvements were required over time, and beginning in 2004, OBDII was phased into the EPA’s “heavy-duty” class (8,500- to 14,000-pound GVWR). As of 2007, all vehicles in this weight class sold in the United States must be OBDII compliant.


Since 1997, federal diesel-powered pickups and vans have been offered with an OBDII exemption for a number of model years. Onboard diagnostics were necessary on these vehicles, but they did not have to be as extensive as their OBDII equivalents. What was the difference between the federal versions and OBDII automobiles marketed in California and other states that embraced California emission standards?

The majority of the variances were in individual Powertrain Control Module (PCM) calibrations, as both versions used the same serial data bus, data connection connector, and basic PCM software. The federal models had fewer supported monitors, but both used the same general and enhanced scan tool modes. With a quick visual assessment, it would be difficult to discern any significant differences.

The glow plug system was an exception in some cars, where various hardware may be employed to regulate and monitor glow plug performance. Glow plug monitors were not necessary in federal vehicles, but they had to be able to diagnose a faulty glow plug, set a Diagnostic Trouble Code (DTC), and turn on the Malfunction Indicator Light (MIL) correspondingly in California vehicles. The federal (OBDI) calibration for a 2003 Ford 6.0 liter turbodiesel is detailed in the sidebar. Overall, the MIL is far less likely to be illuminated in federal vehicles than it is in California models that are OBDII-compliant.

Diesel Engine Monitors

The operation of the supported monitors is critical to the operations of an OBDII-compliant emission control system. All components and systems that play a substantial part in the vehicle’s emissions production must be monitored with OBDII, and one or more of the following tests must be performed:

Electrical tests are carried out. Sensors and actuators are checked for continuity, short circuits, signal out-of-range, and other issues.

Tests of rationalism. deciding whether the data supplied makes sense in light of additional data input in the case of sensors

Tests that are functional. Identifying whether a device is appropriately responding to computer commands.

Active or passive methods can be used to conduct functional tests. During normal operation, passive testing involves waiting for an actuator to get an instruction from the vehicle’s computer and then searching for sensory data that indicates appropriate operation. In active testing, the computer takes control of the actuator solely for the purpose of testing.

A number of monitors, similar to those used in gasoline engines, are employed in diesel engines. Comprehensive component monitoring and exhaust gas recirculation are just two examples. There’s also a misfire monitor, but it’s only active when the computer is inactive. Components that were once only found in gasoline engines are increasingly being utilised in diesel engines to provide monitoring duties.

The Mass Air Flow (MAF) sensor, which is now utilized with diesel engines to monitor the operation of the Exhaust Gas Recirculation (EGR) system, is an excellent example of this. Total airflow into the engine is recorded when the EGR valve is closed, and an associated decline in airflow is expected as the EGR valve opens, much as it is in gasoline applications.

In some circumstances, this new value is compared to a speed-density computation based on the engine’s rpm signal and a Manifold Absolute Pressure (MAP) sensor. The effective EGR gas flow is the difference between the two readings, and it is compared to what the vehicle’s computer requested to establish whether a defect exists in the system.

While diesel engines have some monitors in common with gasoline engines, they also have several that are specific to diesels. The EGR cooler monitor is one example. The exhaust gas recirculation system is critical for reducing nitrogen oxide (NOx) emissions from modern diesel engines. To accomplish the intended effect, very high rates of EGR flow are required, and the EGR gases must be cooled.

The Ford 6.4 liter Powerstroke, for example, performs this purpose by connecting two liquid-cooled EGR coolers in series. Because the EGR cooler has such a large impact on vehicle emissions, it requires an OBDII monitor to ensure proper operation. Two temperature sensors are utilized to monitor the EGR cooler operation on the 6.4 liter Powerstroke: one on the exhaust manifold as it flows into the EGR system, and one near the EGR valve itself.

The PCM may assess the efficiency of the coolers by looking for a temperature difference between the inlet and outlet sensors with the EGR valve open when the EGR cooler monitor is running. A first failure of this test would result in a pending code and a freeze frame, whereas a second failure would result in a DTC and the MIL being illuminated.

The Diesel Oxidation Catalyst (DOC) efficiency monitor is another example of a monitor that is specific to diesel engines. The DOC is used to oxidize hydrocarbon (HC) and carbon monoxide (CO) pollutants, as well as specific Particulate Matter fractions (PM). Even in California OBDII applications, DOCs have been employed in diesel-powered pickups and vans in the past, but their operation was not monitored. Since the 2007 model year (particularly, vehicles constructed after January 1, 2007), this has changed, and these vehicles must now include a catalyst efficiency monitor in their OBD approach.

While oxygen sensors are used to measure the effectiveness of catalysts in gasoline engines, exhaust gas temperature sensors are most commonly used to determine the efficiency of DOCs. Typically, this monitor will be on while the Diesel Particulate Filter (DPF), which is positioned downstream of the DOC, is actively regenerating. When the exhaust valve is open, a small amount of fuel is injected. When this post-injection fuel enters the DOC, the temperature of the exhaust gas rises as the catalyst oxidizes the surplus HC. At the DOC input, the temperature of the exhaust gases is measured and compared to the values at the outlet.

The amount of fuel injected for DPF regeneration determines the minimal predicted temperature increase. A DTC is set and the MIL is illuminated if the exhaust gas temperature does not rise to the anticipated minimum.

Closed Loop Operation

We can expect closed-loop operating in diesel engines in the not-too-distant future. New piezo-resistive sensors have been created that can be used with a glow plug in the same device. Because the glow plug can reach the combustion chambers of the engine, it is now able to assess cylinder pressures during a combustion event and make fuel control modifications based on this information. Because the ability to limit peak pressures in the combustion chamber also limits NOx generation, this is a big step forward in diesel emission management.

The scan tool for diagnosing diesel engine fuel and emission control system issues can also be supplemented with cylinder pressure data that can be used to perform new and more complex monitors, making it increasingly useful for diagnosing diesel engine fuel and emission control system difficulties.

Is there a monthly fee for FIXD?

No, a subscription is not required to utilize your FIXD sensor. Additional services come with the membership, but scanning your vehicle is always free.

Do you leave FIXD plugged in all the time?

When the sensor is not connecting with the app, it uses very little power, so you may leave it plugged in all the time. We recommend that you remove the sensor if you leave your automobile unattended for more than 3 weeks.

What’s the difference between FIXD and FIXD premium?

The FIXD app, which is available for free, tells you what’s wrong with your automobile and provides maintenance reminders. FIXD Premium gives you complete control over your vehicle maintenance and repairs with additional features and experienced on-call service.

How much does FIXD app cost?

FIXD transforms your vehicle’s issues into easy-to-understand words. Whenever you have a problem, FIXD will inform you of the severity of the situation as well as the repercussions of continuing to drive. FIXD will also notify you when your vehicle requires maintenance, allowing you to extend the life of your vehicle.

FIXD Premium is a new feature! Do you require extra assistance in determining the cause of a problem? For assistance from a trained mechanic, call our toll-free number. Emissions Pre-Check, Issue Forecast, Issue Frequency, and more are all included! FIXD Premium subscriptions are available for $8.99/month for a one-month subscription or $69.99/year for a one-year subscription.

FIXD Premium is available as an in-app purchase. After your free trial expires, your iTunes account will be charged, and auto-renewing (at the same price as the original purchase) will begin 24 hours before the end of the time. Renewals must be canceled 24 hours before the end of the period. When you buy something, you lose your free trial period if you haven’t utilized it yet.