Tech2Tech: EFI/DFI Series (Part III): EFI/DFI Troubleshooting



Figure 1 — A Malfunction Indicator LightBy Dave Worden

In part two of our series on electronic fuel-injection (EFI) and digital fuel-injection (DFI) engines in August 2009 OPE, we covered some components that can be tested but not repaired. This could be due to the component — engine control unit (ECU), an electrical relay, a manifold absolute pressure (MAP) sensor — and/or the cost to repair might be in excess of a new part (a fuel injector). In this article, we will cover troubleshooting the EFI/DFI systems when a fault code is given. Most of the EFI/DFI engines are equipped with a diagnostic lamp or a Malfunction Indicator Light (MIL) (see Figure 1).

Diagnostic Lamp/MIL

Although engines equipped with either a diagnostic lamp or MIL will obviously make the technician’s job much easier as far as identifying the problem, the tech still has to check and repair it correctly. Some technicians refer to them as an “idiot light,” which is a mildly derogatory term that refers to a method of displaying information about a system (e.g. an engine or a piece of factory equipment). Dealing with the DFI system by Kawasaki is easy as long as you read the blink code correctly. They have several common codes that indicate air inlet issues, water temperature, and vacuum and/or pressure concerns. Once you read the blink code, you would then simply go to the sensor in question, verify the part is not functioning correctly, and repair or replace it. To access the self-diagnostic codes in a Kawasaki engine with DFI, turn the key on and the light should flash. If not, check the bulb to make sure it is good; if uncertain, replace the bulb. Also, be sure the battery is in a full state of charge or the bulb may blink slowly. After two seconds, the light should flash if there are fault codes stored. They will be a long blink, followed by short blinks; note the code and refer to the manual for potential issues.

One big key to troubleshooting this system is to make sure you rely on the repair manual supplied by the given manufacturer. There will always be procedures that need to be followed and checked in order to make sure the problem does not arise again. This is important for technicians to remember due to the sheer volume of product they see. Years ago, the engines were fairly simple, and one set of procedures could be used for all. Today, the opposite is true — there are so many variations that it is impossible to know them all by heart. I have a great memory; the only issue is that it is really short!

In the case of Kawasaki engines with DFI, their fault codes are as follows:

  1. 12 — Inlet air temperature sensor open or shorted
  2. 13 — Water temperature sensor open or shorted
  3. 21 — Vacuum pressure sensor open or shorted
  4. 22 — Atmospheric pressure measurement error

NOTE: These could all be wiring connections as well.

With the self-diagnostic system, once the code is identified, it is best to refer to the manual for the appropriate voltage tests and remember to have the battery fully charged to get correct readings. Let’s use an example of receiving a fault code 12 and see where we go to repair this issue.

  1. Turn off the ignition switch.
  2. Disconnect the ECU.
  3. Connect the special adapter tool.
  4. Set the volt meter to DC 10V.
  5. Connect the positive and negative leads to the appropriate terminals.
  6. Turn the ignition switch on. Check the voltage reading, which should be approximately 2.26 – 2.50 V at 68 degrees Fahrenheit.
  7. If the voltage is out of this range, then check the ECU ground and power supply.
  8. Check the wiring.
  9. Check the sensor’s resistance using machine oil, and slowly heat the oil while taking resistance readings. If they are outside the values listed in the manual, replace the sensor.

Figure 2 — Flow charts, such as this life example, are easy-to-understand diagrams showing how steps in a process fit together. This makes them useful tools for communicating how processes work, and for clearly documenting how a particular job is done. Furthermore, mapping out a process in flow-chart format helps you clarify your understanding of the process, and helps you think about where the process can be improved. This may seem like a long, drawn-out process, but you must remember that these sensors are at times working in extreme conditions and with very low voltage. Using a flow chart (see Figure 2) as a teaching instrument, service becomes easier as does a better understanding of the systems.


Kohler MIL

The Kohler EFI engine also uses a MIL that uses a blink code. (NOTE: When the MIL is lit, the engine control unit stores the fault code related to the malfunction. The fault code can be retrieved with the diagnostic disk or by reading the blink code by accessing the MIL. Simply turn the key switch on-off-on-off-on-off within three seconds. The light will then blink, count the blinks, refer to the service manual, and you have the fault.) However, the Kohler engine’s MIL will stay on if there is a fault with the EFI components (see Figure 3). As with the DFI system, once you have accessed the fault codes, you then refer to the service manual to see what the issue could be. The MIL fault codes with Kohler are as follows:

1) 21 — Engine Speed Synchronization

2) 22 — Throttle Position Sensor (TPS)

Figure 3 — A lit Malfunction Indicator Light3) 23 — Engine Control Unit (ECU)

4) 24 — Engine Speed Sensor

5) 31 — Oxygen Sensor (short high/low)

6) 32 — Oxygen Sensor (no charge)

7) 33 — Fuel System/Oxygen Sensor (temporary adaption at limit)

8) 34 — Fuel System/Oxygen Sensor (learned adaption limit)

9) 42 — Oil Temperature Sensor

10) There are more codes based on the liquid-cooled engine, as well as some other changes that have occurred with the system. I believe you now see the value of referring to the service manual or having the diagnostic software program that is available.

As we did earlier, let’s take a look at a fault code and follow a procedure for testing it. We will use fault code 42 — Oil Temperature Sensor:

  1. Check sensor wiring and/or connection.
  2. Engine wiring harness — Check appropriate pin connections.
  3. ECU – Check to harness connection problem.
  4. Engine temperature operating above sensor limit
  5. Remove the temperature sensor from the adapter.
  6. Wipe sensor clean and allow it to reach room temperature (20 degrees C, 68 degrees F).
  7. Unplug the main harness connector from the ECU.
  8. With the sensor connected, check the temperature sensor circuit resistance. The value should be 2375-2625.
  9. Unplug the sensor connector and check sensor.
  10. If the resistance is out of specifications, replace the temperature sensor.
  11. If it is within specifications, check the temperature sensor circuits (input, ground) from the main harness connector to the corresponding terminal in the sensor plug for continuity, damage, etc.

As you can see by this example, if a blink code is accessed, it is a matter of tracing the leads and making the appropriate connections, getting the necessary readings, and then replacing the appropriate part(s). If there is no blink code and the engine is running rough or lacks power, remember it could be engine related! There are times when, as technicians, we see a new engine and/or feature and always think the worst. It seems to be our nature that we always remember the worst-case scenarios. For example, when was the last time you were praised for doing a good job? Tough to recall, isn’t it? When was the last time you were called an S.O.B.? That comes a lot easier! I was called that this morning by a wonderful driver on the road!

With all that being said, I want to share a factual problem that I recently encountered. A customer came into a dealership (name being omitted to protect the innocent!) with a commercial machine and the following complaint: “The unit recently began to hunt and/or surge after 10 minutes of running and now it appears to be getting worse. I just changed the fuel filter, but it is still hunting.” The technician (his name is also being omitted to protect himself!) claimed to check everything, and it appears to be a DFI relay issue. I was asked to check it over and see what I could determine. I went to the Malfunction Indicator Light and checked for a fault code. The light was disconnected, and when I checked further, it was burned out! I asked for a replacement bulb, but the parts department did not have one in stock. (Not a good start.) I then did a visual check to see if there were any other indicators or signs. I observed the following:

  1. The air cleaner canister had duct tape over the elbow. Upon removal of the tape, there was a large piece of the plastic elbow gone!
  2. The fuel cap also had the NASCAR glue (duct tape) holding the fuel cap together!
  3. There was a large amount of debris in the fuel tank itself.

At this point, to be safe, I took a VOA meter and the service manual for DFI engines and did some preliminary tests; all sensors passed their tests and the fuel pressure — when running — was within specifications, but the unit still hunted. I then ran the engine with the air cleaner removed, and when the engine started to surge/hunt, I began to close off the air supply. I had the airflow almost completely cut off, when the engine suddenly smoothed out and ran fine! This led me to believe that the unit was getting too much air and not enough fuel. I then remembered the owner stated he replaced the fuel filter. I checked his filter, which was the correct type and installed correctly. However, when I checked the fuel flow from the tank (Remember the debris?), there was barely any flow from the tank! I removed the fuel line from the tank to the filter, and it was packed with debris and grass! This was restricting the amount of fuel, along with a bad fuel cap and air cleaner. After cleaning and flushing the tank, replacing the fuel cap and air cleaner canister, the engine started and ran fine. I also had a new indicator lamp installed and checked the system, and there were no faults.

What does this prove? My opinion was that the technician was unfamiliar with a DFI system (he did finally admit that), and since he did not understand the system, it had to be a sensor and/or DFI component related. If he had applied basic theory or taken the time to call the manufacturer or at least replaced the indicator lamp, he would have spent less time being frustrated and more time being efficient and productive.

Dave Worden has 40 years of extensive experience in the outdoor power equipment industry at the dealer, distributor and manufacturer levels. After beginning his career as a service technician for a dealership, he made the jump to a Central Distributor. There, he continued to work in the service department before he was promoted to educational director, representing Briggs & Stratton, Kohler, MTD and Tecumseh. He then moved up to the manufacturer level, serving as a territory manager for McCulloch Corp., a training specialist for Kohler Co. Engine Division, and a general manager for a manufacturer-owned dealership. In addition to being a contributing writer for OPE, Worden is currently operating a dealer consulting company called DJW Consultants, as well as serving as vice president of the Equipment & Engine Training Council, a committee chair for National SkillsUSA and an at-large representative for SkillsUSA Massachusetts.


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