Ron Ananian, The Car Doctor - October 11, 2025 - Hour 1 - Diagnosing Fuel Injector Faults - (855)560-9900 24/7 Hotline
About this episode
Ron Ananian dives deep into diagnosing fuel injector faults, specifically focusing on the P0203 code, which indicates an injector circuit fault. He shares a real-life case involving a 2015 Jeep Wrangler experiencing misfires and discusses the importance of testing the entire injector circuit. Listeners will learn about common misconceptions regarding misfires and the significance of proper diagnostics. The episode also touches on winter driving preparedness and features engaging listener calls about classic cars and electrical issues, providing practical advice and insights from Ron's extensive experience.
Code P0203, winter-readiness, and two electrical gremlins. Ron opens with a 2015 Jeep Wrangler 3.6L that set P0303 (misfire) and P0203 (injector circuit). He walks through smart diagnostics: verify injector resistance against known-good cylinders, check the circuit from PCM to injector, then confirm with a scope or a swap test—because a component can ohm “good” cold and fail hot. From there, he pivots to fall-and-winter driving prep in response to an RV-fire traffic shutdown: fuel up, pack essentials, and plan for long, no-exit stretches. Classic-iron detour: documenting a ’67 Chevy II Nova (VIN/cowl tag and build sheet beat a window sticker). Then it’s a ’96 Olds Aurora with a fickle charge (don’t trust the dash—test the alternator feed and wiring) and an ’09 Escape no-crank likely flirting with anti-theft/steering-lock issues.
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P0203
"I want to talk about P0203. P0203 is a fault code."
P0203 is a code that mechanics use to identify problems with the fuel injector for the third cylinder in an engine. If this code appears, it usually means there might be an issue with how fuel is being delivered to that part of the engine.
P0203 is an OBD-II fault code that indicates a problem with the fuel injector circuit for cylinder 3. This code can help diagnose issues related to fuel delivery or injector malfunction.
Jeep Wrangler
"We had a 2015 Jeep Wrangler, V6 to 3.6, came into the shop this week..."
The Jeep Wrangler is a tough, off-road vehicle that can handle rough terrain. The 2015 version has a V6 engine, which gives it good power for driving in challenging conditions.
The Jeep Wrangler is a compact and mid-size four-wheel drive off-road vehicle known for its rugged design and off-road capabilities. The 2015 model features a V6 engine, which is popular among enthusiasts for its balance of power and efficiency.
cylinder misfire
"It's reported P0303, cylinder misfire, P0203, injector circuit fault."
A cylinder misfire happens when a part of the engine doesn't work right, causing the engine to run unevenly and lose power. This can be due to problems with spark plugs or fuel delivery.
A cylinder misfire occurs when one or more cylinders in an engine fail to fire properly, leading to rough engine performance and a loss of power. It can be caused by issues such as faulty spark plugs, fuel injectors, or ignition coils.
injector circuit fault
"P0303, cylinder misfire, P0203, injector circuit fault."
An injector circuit fault means there's a problem with the part that controls how fuel gets into the engine. If this isn't working, the engine might not run well.
An injector circuit fault indicates a problem with the electrical circuit that controls the fuel injector, which can prevent the injector from delivering fuel to the engine properly. This can lead to performance issues and misfires.
check engine light
"and the check engine light comes on and the light starts to flash,"
The check engine light is a light on your dashboard that tells you something might be wrong with your car's engine. If it comes on, it's a good idea to get it checked out.
The check engine light is a warning indicator on a vehicle's dashboard that signals a potential issue with the engine or emissions system. When it illuminates, it indicates that the vehicle's onboard diagnostics have detected a problem that may need attention.
spark plug
"it needs a spark plug, right?"
A spark plug is a part of your car's engine that helps start the engine by creating a small spark. If it’s not working well, your car can have trouble running smoothly.
A spark plug is a crucial component in gasoline engines that ignites the air-fuel mixture in the combustion chamber. Proper functioning of spark plugs is essential for engine performance, fuel efficiency, and emissions control.
injector connector
"And it was a simple process to get to the injector connector, unplug it, and we read about 14 ohms of resistance."
An injector connector is a part that connects to the fuel injector, helping it get the electrical signals it needs to spray fuel into the engine.
The injector connector is a component that connects the fuel injector to the vehicle's electrical system. It allows the injector to receive the necessary electrical signals to operate correctly.
ohms
"...we read about 14 ohms of resistance. Well, the circuit, and I know this just from having done these before..."
Ohms measure how much resistance there is to electricity. In cars, this helps check if parts like fuel injectors are working correctly.
Ohms is a unit of measurement for electrical resistance. In automotive contexts, it helps determine if electrical components are functioning properly by measuring how much resistance they present to the flow of electricity.
resistance
"...the circuit, and I know this just from having done these before, those injectors typically read between 10, 10 and 16 ohms of resistance."
Resistance is how much a part opposes the flow of electricity. It's important for checking if electrical parts in cars are working properly.
Resistance in electrical terms refers to the opposition to the flow of electric current. In automotive applications, measuring resistance can help diagnose electrical issues in components like sensors and injectors.
ASD relay
"you have to pull out the ASD relay, the automatic shutdown relay. And I checked the circuit live."
The ASD relay is a part of the car's electrical system that turns off the fuel and ignition if something goes wrong. This helps keep the engine safe from damage.
The Automatic Shutdown Relay (ASD relay) is a component in a vehicle's electrical system that controls the power to the fuel injectors and ignition system. It helps prevent the engine from running when there is a fault, ensuring safety and preventing damage.
PCM
"...termination at the PCM out to the injector to make sure that it read the same and it did."
The PCM is like the brain of the car that controls how the engine and transmission work together. It helps the car run smoothly by making adjustments based on information it receives from sensors.
The Powertrain Control Module (PCM) is the computer that manages the engine and transmission functions in a vehicle. It processes data from various sensors and makes adjustments to optimize performance and efficiency.
P0201
"My problem now, I set a P0201 diagnosis confirmed. I've got a bad injector that measured correctly as far as resistance..."
P0201 is a code that tells you there's a problem with the fuel injector for the first cylinder in the engine. It helps mechanics figure out what's wrong.
P0201 is a diagnostic trouble code (DTC) indicating a problem with the injector circuit for cylinder one. It helps mechanics identify issues related to fuel delivery in that specific cylinder.
wiring harness
"...especially on the Jeeps where the wiring harness runs up and around the intake plenum is, we're looking for critters, right?"
A wiring harness is like a network of wires that connects different parts of a car, allowing them to communicate and work together. If it's damaged, it can cause electrical problems.
A wiring harness is a bundle of wires and connectors that transmits electrical power and signals throughout a vehicle. It's crucial for the functioning of various electrical components, including the engine and sensors.
injectors
"Put a set of injectors in it, all right? At my suggestion, the customer agreed, higher mileage, older vehicle."
Injectors are parts of a car's engine that spray fuel into the engine to help it run. If they get old or damaged, the car might not work as well.
Fuel injectors are components in an engine that deliver fuel into the combustion chamber. They play a crucial role in the engine's performance and efficiency, especially in older vehicles where they may wear out over time.
Chevy II Nova
"...how can I help? 1967 Chevy II Nova,"
The Chevy II Nova is a small car made by Chevrolet that was popular in the 1960s. The 1967 version is known for being affordable and easy to maintain, making it a favorite among car lovers.
The Chevy II Nova is a compact car produced by Chevrolet from 1962 to 1979. The 1967 model year is part of the second generation, known for its simple design and affordability, making it popular among car enthusiasts and collectors.
Chevrolet Chevy II
"All right, how can I help? 1967 Chevy II Nova, been decoding the Protector plate"
The Chevy II, or Nova, is a small car that was made in the 1960s and is loved for its simple design and good performance. The 1967 model is especially popular among people who like classic cars because it looks cool and has a lot of power.
The Chevrolet Chevy II, also known as the Nova, was introduced in the early 1960s as a compact car aimed at providing an affordable and efficient option for buyers. The 1967 model is particularly notable for its classic styling and performance options, making it a favorite among classic car enthusiasts and collectors.
Protector plate
"The Protector plate, the engine code on the Protector plate is ZI, and I traced that back to being a L79."
A Protector plate is a small metal tag on a car that shows details like the engine type. It's used to check if the car's parts are original and correct.
The Protector plate is a metal plate attached to a vehicle that contains important information about the car, such as the engine code and other specifications. It is often used for verifying the authenticity and originality of classic cars.
L79
"...I traced that back to being a L79. But then, like I said, the window sticker..."
The L79 is a powerful engine that was used in some older Chevrolet cars. It's popular among car fans because it offers good performance.
The L79 is a high-performance engine option that was available in some classic Chevrolet models, particularly in the 1960s. It is known for its power and was often sought after by enthusiasts.
CE block
"The 327, this is where the twist is, it's got a CE block in it, and it's got L79 pistons in it, because I put a camera in there and looked at the, the number on top of the piston..."
A CE block is a type of engine block used in some Chevrolet cars. It helps identify what kind of engine it is and what parts can be used with it.
A CE block refers to a specific casting number for a Chevrolet engine block, indicating its design and specifications. This designation is important for identifying the engine's capabilities and compatibility with performance parts.
casting number
"...because I put a camera in there and looked at the, the number on top of the piston, and it's 3866954."
A casting number is a special code found on engine parts that helps identify what the part is and its specifications. It's like a name tag for engine components.
A casting number is a unique identifier stamped on engine components, such as blocks and pistons, that indicates the part's specifications and manufacturing details. It is crucial for identifying the correct parts for repairs or upgrades.
horsepower
"to ruin an engine in one of those because of the horsepower they put out. So, I think it really comes back to..."
Horsepower is a way to measure how powerful an engine is. The more horsepower an engine has, the faster and stronger it can make a car go.
Horsepower is a unit of measurement for power, commonly used to quantify the output of engines. It indicates how much work an engine can perform over time, influencing a vehicle's acceleration and top speed.
Chevrolet Chevelle
"...but he had a 65 Chevelle SS 396 car. By the time he got it in the early 70s,..."
The Chevelle SS 396 is a classic American muscle car from 1965. It was known for its strong engine and sporty design, making it popular among car enthusiasts.
The Chevrolet Chevelle SS 396 is a classic muscle car known for its powerful engine and performance. The 'SS' stands for Super Sport, indicating a higher performance variant of the Chevelle.
big block
"it had a 283 in it because the original big block was gone."
A big block is a type of car engine that is larger and usually provides more power than smaller engines. It's often found in muscle cars and performance vehicles.
A big block refers to a type of engine design that has a larger displacement and is typically more powerful than small block engines. They are often used in high-performance applications.
automotive history
"...But that was a piece of automotive history. I think those were the cars the first year 65..."
Automotive history is the story of how cars have been made and changed over the years. It includes important cars and inventions that have influenced how we drive today.
Automotive history refers to the development and evolution of motor vehicles over time, including significant models, technological advancements, and cultural impacts. The mention of 'automotive history' highlights the importance of certain cars, like the Chevelle, in shaping the automotive landscape.
older cars
"...the problem with all the older cars, it's not that they won't go the distance, but if they break, you can't buy parts..."
Older cars are vehicles that were made a long time ago. They might not work as well for long trips because they can break down more easily and finding parts to fix them can be hard.
Older cars often refer to vehicles manufactured several decades ago, typically before the 1980s. They may lack modern technology and safety features, making them less reliable for long-distance travel compared to newer models.
Chevrolet Monte Carlo
"I went to college in a 72 Monte Carlo And, you know, I broke down on the side of the Garden State Parkway."
The Chevrolet Monte Carlo is a type of car made by Chevrolet, popular in the 1970s. The 1972 version is known for being stylish and having good performance.
The Chevrolet Monte Carlo is a personal luxury car that was produced by Chevrolet from 1970 to 1988. The 1972 model is part of the first generation, known for its stylish design and performance options.
327
"I think it was a 327 350 horse car. And it was very rare and very, very much sought after then as it is today."
The '327' is a type of engine size used in some classic cars, especially Chevrolets. It's known for being powerful and is often sought after by car enthusiasts.
The '327' refers to a 327 cubic inch V8 engine, commonly associated with Chevrolet. This engine was popular in various models during the 1960s and is known for its performance and reliability.
voltage regulator
"...so I don't know what the voltage regulator is at. Well, the voltage regulator is built into the alternator."
The voltage regulator is a part that helps control the amount of electricity that goes to the battery and other electrical parts of the car, making sure they get the right amount of power.
The voltage regulator is a component that maintains a constant voltage level to the electrical system, ensuring that the battery and electrical components receive the correct voltage to operate efficiently.
Ford Escape
".... Tell me your story. Okay, so I got a 2009 Ford Escape. About six months ago,"
The Ford Escape is a small SUV that is great for driving around town or taking on trips. The 2009 version is known for being comfortable and having enough space for passengers and luggage, plus it even has a version that saves on gas.
The Ford Escape is a compact SUV that was first introduced in 2000 and has become popular for its blend of practicality and efficiency. The 2009 model is part of the second generation and is known for its comfortable ride, spacious interior, and available hybrid variant, making it a significant choice for families and commuters alike.
OBD2
"Now I'm not talking about something OBD2, do you have something that'll go year make model?"
OBD2 is a system in cars that helps check if everything is working properly. It can tell mechanics if there are any problems with the engine or other important parts.
OBD2 stands for On-Board Diagnostics II, a standardized system that allows vehicles to self-diagnose and report issues. It provides access to data from the vehicle's engine control unit and other systems, helping mechanics identify problems more efficiently.
voltmeter
"...I'd put a voltmeter on it. Okay. Because I just want to know, do I have signal?"
A voltmeter is a device that checks how much electricity is flowing through a wire. It's useful for figuring out if there's a problem with the car's electrical system.
A voltmeter is a tool used to measure the electrical potential difference, or voltage, between two points in an electrical circuit. It is essential for diagnosing electrical issues in vehicles.
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